ssa.go

// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gc

import (
	"encoding/binary"
	"fmt"
	"html"
	"os"
	"path/filepath"
	"sort"

	"bufio"
	"bytes"
	"cmd/compile/internal/ssa"
	"cmd/compile/internal/types"
	"cmd/internal/obj"
	"cmd/internal/obj/x86"
	"cmd/internal/objabi"
	"cmd/internal/src"
	"cmd/internal/sys"
)

var ssaConfig *ssa.Config
var ssaCaches []ssa.Cache

var ssaDump string     // early copy of $GOSSAFUNC; the func name to dump output for
var ssaDir string      // optional destination for ssa dump file
var ssaDumpStdout bool // whether to dump to stdout
var ssaDumpCFG string  // generate CFGs for these phases
const ssaDumpFile = "ssa.html"

// The max number of defers in a function using open-coded defers. We enforce this
// limit because the deferBits bitmask is currently a single byte (to minimize code size)
const maxOpenDefers = 8

// ssaDumpInlined holds all inlined functions when ssaDump contains a function name.
var ssaDumpInlined []*Node

func initssaconfig() {
	types_ := ssa.NewTypes()

	if thearch.SoftFloat {
		softfloatInit()
	}

	// Generate a few pointer types that are uncommon in the frontend but common in the backend.
	// Caching is disabled in the backend, so generating these here avoids allocations.
	_ = types.NewPtr(types.Types[TINTER])                             // *interface{}
	_ = types.NewPtr(types.NewPtr(types.Types[TSTRING]))              // **string
	_ = types.NewPtr(types.NewSlice(types.Types[TINTER]))             // *[]interface{}
	_ = types.NewPtr(types.NewPtr(types.Bytetype))                    // **byte
	_ = types.NewPtr(types.NewSlice(types.Bytetype))                  // *[]byte
	_ = types.NewPtr(types.NewSlice(types.Types[TSTRING]))            // *[]string
	_ = types.NewPtr(types.NewPtr(types.NewPtr(types.Types[TUINT8]))) // ***uint8
	_ = types.NewPtr(types.Types[TINT16])                             // *int16
	_ = types.NewPtr(types.Types[TINT64])                             // *int64
	_ = types.NewPtr(types.Errortype)                                 // *error
	types.NewPtrCacheEnabled = false
	ssaConfig = ssa.NewConfig(thearch.LinkArch.Name, *types_, Ctxt, Debug.N == 0)
	ssaConfig.SoftFloat = thearch.SoftFloat
	ssaConfig.Race = flag_race
	ssaCaches = make([]ssa.Cache, nBackendWorkers)

	// Set up some runtime functions we'll need to call.
	assertE2I = sysfunc("assertE2I")
	assertE2I2 = sysfunc("assertE2I2")
	assertI2I = sysfunc("assertI2I")
	assertI2I2 = sysfunc("assertI2I2")
	deferproc = sysfunc("deferproc")
	deferprocStack = sysfunc("deferprocStack")
	Deferreturn = sysfunc("deferreturn")
	Duffcopy = sysfunc("duffcopy")
	Duffzero = sysfunc("duffzero")
	gcWriteBarrier = sysfunc("gcWriteBarrier")
	goschedguarded = sysfunc("goschedguarded")
	growslice = sysfunc("growslice")
	msanread = sysfunc("msanread")
	msanwrite = sysfunc("msanwrite")
	msanmove = sysfunc("msanmove")
	newobject = sysfunc("newobject")
	newproc = sysfunc("newproc")
	panicdivide = sysfunc("panicdivide")
	panicdottypeE = sysfunc("panicdottypeE")
	panicdottypeI = sysfunc("panicdottypeI")
	panicnildottype = sysfunc("panicnildottype")
	panicoverflow = sysfunc("panicoverflow")
	panicshift = sysfunc("panicshift")
	raceread = sysfunc("raceread")
	racereadrange = sysfunc("racereadrange")
	racewrite = sysfunc("racewrite")
	racewriterange = sysfunc("racewriterange")
	x86HasPOPCNT = sysvar("x86HasPOPCNT")       // bool
	x86HasSSE41 = sysvar("x86HasSSE41")         // bool
	x86HasFMA = sysvar("x86HasFMA")             // bool
	armHasVFPv4 = sysvar("armHasVFPv4")         // bool
	arm64HasATOMICS = sysvar("arm64HasATOMICS") // bool
	typedmemclr = sysfunc("typedmemclr")
	typedmemmove = sysfunc("typedmemmove")
	Udiv = sysvar("udiv")                 // asm func with special ABI
	writeBarrier = sysvar("writeBarrier") // struct { bool; ... }
	zerobaseSym = sysvar("zerobase")

	// asm funcs with special ABI
	if thearch.LinkArch.Name == "amd64" {
		GCWriteBarrierReg = map[int16]*obj.LSym{
			x86.REG_AX: sysfunc("gcWriteBarrier"),
			x86.REG_CX: sysfunc("gcWriteBarrierCX"),
			x86.REG_DX: sysfunc("gcWriteBarrierDX"),
			x86.REG_BX: sysfunc("gcWriteBarrierBX"),
			x86.REG_BP: sysfunc("gcWriteBarrierBP"),
			x86.REG_SI: sysfunc("gcWriteBarrierSI"),
			x86.REG_R8: sysfunc("gcWriteBarrierR8"),
			x86.REG_R9: sysfunc("gcWriteBarrierR9"),
		}
	}

	if thearch.LinkArch.Family == sys.Wasm {
		BoundsCheckFunc[ssa.BoundsIndex] = sysfunc("goPanicIndex")
		BoundsCheckFunc[ssa.BoundsIndexU] = sysfunc("goPanicIndexU")
		BoundsCheckFunc[ssa.BoundsSliceAlen] = sysfunc("goPanicSliceAlen")
		BoundsCheckFunc[ssa.BoundsSliceAlenU] = sysfunc("goPanicSliceAlenU")
		BoundsCheckFunc[ssa.BoundsSliceAcap] = sysfunc("goPanicSliceAcap")
		BoundsCheckFunc[ssa.BoundsSliceAcapU] = sysfunc("goPanicSliceAcapU")
		BoundsCheckFunc[ssa.BoundsSliceB] = sysfunc("goPanicSliceB")
		BoundsCheckFunc[ssa.BoundsSliceBU] = sysfunc("goPanicSliceBU")
		BoundsCheckFunc[ssa.BoundsSlice3Alen] = sysfunc("goPanicSlice3Alen")
		BoundsCheckFunc[ssa.BoundsSlice3AlenU] = sysfunc("goPanicSlice3AlenU")
		BoundsCheckFunc[ssa.BoundsSlice3Acap] = sysfunc("goPanicSlice3Acap")
		BoundsCheckFunc[ssa.BoundsSlice3AcapU] = sysfunc("goPanicSlice3AcapU")
		BoundsCheckFunc[ssa.BoundsSlice3B] = sysfunc("goPanicSlice3B")
		BoundsCheckFunc[ssa.BoundsSlice3BU] = sysfunc("goPanicSlice3BU")
		BoundsCheckFunc[ssa.BoundsSlice3C] = sysfunc("goPanicSlice3C")
		BoundsCheckFunc[ssa.BoundsSlice3CU] = sysfunc("goPanicSlice3CU")
	} else {
		BoundsCheckFunc[ssa.BoundsIndex] = sysfunc("panicIndex")
		BoundsCheckFunc[ssa.BoundsIndexU] = sysfunc("panicIndexU")
		BoundsCheckFunc[ssa.BoundsSliceAlen] = sysfunc("panicSliceAlen")
		BoundsCheckFunc[ssa.BoundsSliceAlenU] = sysfunc("panicSliceAlenU")
		BoundsCheckFunc[ssa.BoundsSliceAcap] = sysfunc("panicSliceAcap")
		BoundsCheckFunc[ssa.BoundsSliceAcapU] = sysfunc("panicSliceAcapU")
		BoundsCheckFunc[ssa.BoundsSliceB] = sysfunc("panicSliceB")
		BoundsCheckFunc[ssa.BoundsSliceBU] = sysfunc("panicSliceBU")
		BoundsCheckFunc[ssa.BoundsSlice3Alen] = sysfunc("panicSlice3Alen")
		BoundsCheckFunc[ssa.BoundsSlice3AlenU] = sysfunc("panicSlice3AlenU")
		BoundsCheckFunc[ssa.BoundsSlice3Acap] = sysfunc("panicSlice3Acap")
		BoundsCheckFunc[ssa.BoundsSlice3AcapU] = sysfunc("panicSlice3AcapU")
		BoundsCheckFunc[ssa.BoundsSlice3B] = sysfunc("panicSlice3B")
		BoundsCheckFunc[ssa.BoundsSlice3BU] = sysfunc("panicSlice3BU")
		BoundsCheckFunc[ssa.BoundsSlice3C] = sysfunc("panicSlice3C")
		BoundsCheckFunc[ssa.BoundsSlice3CU] = sysfunc("panicSlice3CU")
	}
	if thearch.LinkArch.PtrSize == 4 {
		ExtendCheckFunc[ssa.BoundsIndex] = sysvar("panicExtendIndex")
		ExtendCheckFunc[ssa.BoundsIndexU] = sysvar("panicExtendIndexU")
		ExtendCheckFunc[ssa.BoundsSliceAlen] = sysvar("panicExtendSliceAlen")
		ExtendCheckFunc[ssa.BoundsSliceAlenU] = sysvar("panicExtendSliceAlenU")
		ExtendCheckFunc[ssa.BoundsSliceAcap] = sysvar("panicExtendSliceAcap")
		ExtendCheckFunc[ssa.BoundsSliceAcapU] = sysvar("panicExtendSliceAcapU")
		ExtendCheckFunc[ssa.BoundsSliceB] = sysvar("panicExtendSliceB")
		ExtendCheckFunc[ssa.BoundsSliceBU] = sysvar("panicExtendSliceBU")
		ExtendCheckFunc[ssa.BoundsSlice3Alen] = sysvar("panicExtendSlice3Alen")
		ExtendCheckFunc[ssa.BoundsSlice3AlenU] = sysvar("panicExtendSlice3AlenU")
		ExtendCheckFunc[ssa.BoundsSlice3Acap] = sysvar("panicExtendSlice3Acap")
		ExtendCheckFunc[ssa.BoundsSlice3AcapU] = sysvar("panicExtendSlice3AcapU")
		ExtendCheckFunc[ssa.BoundsSlice3B] = sysvar("panicExtendSlice3B")
		ExtendCheckFunc[ssa.BoundsSlice3BU] = sysvar("panicExtendSlice3BU")
		ExtendCheckFunc[ssa.BoundsSlice3C] = sysvar("panicExtendSlice3C")
		ExtendCheckFunc[ssa.BoundsSlice3CU] = sysvar("panicExtendSlice3CU")
	}

	// Wasm (all asm funcs with special ABIs)
	WasmMove = sysvar("wasmMove")
	WasmZero = sysvar("wasmZero")
	WasmDiv = sysvar("wasmDiv")
	WasmTruncS = sysvar("wasmTruncS")
	WasmTruncU = sysvar("wasmTruncU")
	SigPanic = sysfunc("sigpanic")
}

// getParam returns the Field of ith param of node n (which is a
// function/method/interface call), where the receiver of a method call is
// considered as the 0th parameter. This does not include the receiver of an
// interface call.
func getParam(n *Node, i int) *types.Field {
	t := n.Left.Type
	if n.Op == OCALLMETH {
		if i == 0 {
			return t.Recv()
		}
		return t.Params().Field(i - 1)
	}
	return t.Params().Field(i)
}

// dvarint writes a varint v to the funcdata in symbol x and returns the new offset
func dvarint(x *obj.LSym, off int, v int64) int {
	if v < 0 || v > 1e9 {
		panic(fmt.Sprintf("dvarint: bad offset for funcdata - %v", v))
	}
	if v < 1<<7 {
		return duint8(x, off, uint8(v))
	}
	off = duint8(x, off, uint8((v&127)|128))
	if v < 1<<14 {
		return duint8(x, off, uint8(v>>7))
	}
	off = duint8(x, off, uint8(((v>>7)&127)|128))
	if v < 1<<21 {
		return duint8(x, off, uint8(v>>14))
	}
	off = duint8(x, off, uint8(((v>>14)&127)|128))
	if v < 1<<28 {
		return duint8(x, off, uint8(v>>21))
	}
	off = duint8(x, off, uint8(((v>>21)&127)|128))
	return duint8(x, off, uint8(v>>28))
}

// emitOpenDeferInfo emits FUNCDATA information about the defers in a function
// that is using open-coded defers.  This funcdata is used to determine the active
// defers in a function and execute those defers during panic processing.
//
// The funcdata is all encoded in varints (since values will almost always be less than
// 128, but stack offsets could potentially be up to 2Gbyte). All "locations" (offsets)
// for stack variables are specified as the number of bytes below varp (pointer to the
// top of the local variables) for their starting address. The format is:
//
//  - Max total argument size among all the defers
//  - Offset of the deferBits variable
//  - Number of defers in the function
//  - Information about each defer call, in reverse order of appearance in the function:
//    - Total argument size of the call
//    - Offset of the closure value to call
//    - Number of arguments (including interface receiver or method receiver as first arg)
//    - Information about each argument
//      - Offset of the stored defer argument in this function's frame
//      - Size of the argument
//      - Offset of where argument should be placed in the args frame when making call
func (s *state) emitOpenDeferInfo() {
	x := Ctxt.Lookup(s.curfn.Func.lsym.Name + ".opendefer")
	s.curfn.Func.lsym.Func().OpenCodedDeferInfo = x
	off := 0

	// Compute maxargsize (max size of arguments for all defers)
	// first, so we can output it first to the funcdata
	var maxargsize int64
	for i := len(s.openDefers) - 1; i >= 0; i-- {
		r := s.openDefers[i]
		argsize := r.n.Left.Type.ArgWidth()
		if argsize > maxargsize {
			maxargsize = argsize
		}
	}
	off = dvarint(x, off, maxargsize)
	off = dvarint(x, off, -s.deferBitsTemp.Xoffset)
	off = dvarint(x, off, int64(len(s.openDefers)))

	// Write in reverse-order, for ease of running in that order at runtime
	for i := len(s.openDefers) - 1; i >= 0; i-- {
		r := s.openDefers[i]
		off = dvarint(x, off, r.n.Left.Type.ArgWidth())
		off = dvarint(x, off, -r.closureNode.Xoffset)
		numArgs := len(r.argNodes)
		if r.rcvrNode != nil {
			// If there's an interface receiver, treat/place it as the first
			// arg. (If there is a method receiver, it's already included as
			// first arg in r.argNodes.)
			numArgs++
		}
		off = dvarint(x, off, int64(numArgs))
		if r.rcvrNode != nil {
			off = dvarint(x, off, -r.rcvrNode.Xoffset)
			off = dvarint(x, off, s.config.PtrSize)
			off = dvarint(x, off, 0)
		}
		for j, arg := range r.argNodes {
			f := getParam(r.n, j)
			off = dvarint(x, off, -arg.Xoffset)
			off = dvarint(x, off, f.Type.Size())
			off = dvarint(x, off, f.Offset)
		}
	}
}

// buildssa builds an SSA function for fn.
// worker indicates which of the backend workers is doing the processing.
func buildssa(fn *Node, worker int) *ssa.Func {
	name := fn.funcname()
	printssa := false
	if ssaDump != "" { // match either a simple name e.g. "(*Reader).Reset", or a package.name e.g. "compress/gzip.(*Reader).Reset"
		printssa = name == ssaDump || myimportpath+"."+name == ssaDump
	}
	var astBuf *bytes.Buffer
	if printssa {
		astBuf = &bytes.Buffer{}
		fdumplist(astBuf, "buildssa-enter", fn.Func.Enter)
		fdumplist(astBuf, "buildssa-body", fn.Nbody)
		fdumplist(astBuf, "buildssa-exit", fn.Func.Exit)
		if ssaDumpStdout {
			fmt.Println("generating SSA for", name)
			fmt.Print(astBuf.String())
		}
	}

	var s state
	s.pushLine(fn.Pos)
	defer s.popLine()

	s.hasdefer = fn.Func.HasDefer()
	if fn.Func.Pragma&CgoUnsafeArgs != 0 {
		s.cgoUnsafeArgs = true
	}

	fe := ssafn{
		curfn: fn,
		log:   printssa && ssaDumpStdout,
	}
	s.curfn = fn

	s.f = ssa.NewFunc(&fe)
	s.config = ssaConfig
	s.f.Type = fn.Type
	s.f.Config = ssaConfig
	s.f.Cache = &ssaCaches[worker]
	s.f.Cache.Reset()
	s.f.Name = name
	s.f.DebugTest = s.f.DebugHashMatch("GOSSAHASH")
	s.f.PrintOrHtmlSSA = printssa
	if fn.Func.Pragma&Nosplit != 0 {
		s.f.NoSplit = true
	}
	s.panics = map[funcLine]*ssa.Block{}
	s.softFloat = s.config.SoftFloat

	// Allocate starting block
	s.f.Entry = s.f.NewBlock(ssa.BlockPlain)
	s.f.Entry.Pos = fn.Pos

	if printssa {
		ssaDF := ssaDumpFile
		if ssaDir != "" {
			ssaDF = filepath.Join(ssaDir, myimportpath+"."+name+".html")
			ssaD := filepath.Dir(ssaDF)
			os.MkdirAll(ssaD, 0755)
		}
		s.f.HTMLWriter = ssa.NewHTMLWriter(ssaDF, s.f, ssaDumpCFG)
		// TODO: generate and print a mapping from nodes to values and blocks
		dumpSourcesColumn(s.f.HTMLWriter, fn)
		s.f.HTMLWriter.WriteAST("AST", astBuf)
	}

	// Allocate starting values
	s.labels = map[string]*ssaLabel{}
	s.labeledNodes = map[*Node]*ssaLabel{}
	s.fwdVars = map[*Node]*ssa.Value{}
	s.startmem = s.entryNewValue0(ssa.OpInitMem, types.TypeMem)

	s.hasOpenDefers = Debug.N == 0 && s.hasdefer && !s.curfn.Func.OpenCodedDeferDisallowed()
	switch {
	case s.hasOpenDefers && (Ctxt.Flag_shared || Ctxt.Flag_dynlink) && thearch.LinkArch.Name == "386":
		// Don't support open-coded defers for 386 ONLY when using shared
		// libraries, because there is extra code (added by rewriteToUseGot())
		// preceding the deferreturn/ret code that is generated by gencallret()
		// that we don't track correctly.
		s.hasOpenDefers = false
	}
	if s.hasOpenDefers && s.curfn.Func.Exit.Len() > 0 {
		// Skip doing open defers if there is any extra exit code (likely
		// copying heap-allocated return values or race detection), since
		// we will not generate that code in the case of the extra
		// deferreturn/ret segment.
		s.hasOpenDefers = false
	}
	if s.hasOpenDefers &&
		s.curfn.Func.numReturns*s.curfn.Func.numDefers > 15 {
		// Since we are generating defer calls at every exit for
		// open-coded defers, skip doing open-coded defers if there are
		// too many returns (especially if there are multiple defers).
		// Open-coded defers are most important for improving performance
		// for smaller functions (which don't have many returns).
		s.hasOpenDefers = false
	}

	s.sp = s.entryNewValue0(ssa.OpSP, types.Types[TUINTPTR]) // TODO: use generic pointer type (unsafe.Pointer?) instead
	s.sb = s.entryNewValue0(ssa.OpSB, types.Types[TUINTPTR])

	s.startBlock(s.f.Entry)
	s.vars[&memVar] = s.startmem
	if s.hasOpenDefers {
		// Create the deferBits variable and stack slot.  deferBits is a
		// bitmask showing which of the open-coded defers in this function
		// have been activated.
		deferBitsTemp := tempAt(src.NoXPos, s.curfn, types.Types[TUINT8])
		s.deferBitsTemp = deferBitsTemp
		// For this value, AuxInt is initialized to zero by default
		startDeferBits := s.entryNewValue0(ssa.OpConst8, types.Types[TUINT8])
		s.vars[&deferBitsVar] = startDeferBits
		s.deferBitsAddr = s.addr(deferBitsTemp)
		s.store(types.Types[TUINT8], s.deferBitsAddr, startDeferBits)
		// Make sure that the deferBits stack slot is kept alive (for use
		// by panics) and stores to deferBits are not eliminated, even if
		// all checking code on deferBits in the function exit can be
		// eliminated, because the defer statements were all
		// unconditional.
		s.vars[&memVar] = s.newValue1Apos(ssa.OpVarLive, types.TypeMem, deferBitsTemp, s.mem(), false)
	}

	// Generate addresses of local declarations
	s.decladdrs = map[*Node]*ssa.Value{}
	var args []ssa.Param
	var results []ssa.Param
	for _, n := range fn.Func.Dcl {
		switch n.Class() {
		case PPARAM:
			s.decladdrs[n] = s.entryNewValue2A(ssa.OpLocalAddr, types.NewPtr(n.Type), n, s.sp, s.startmem)
			args = append(args, ssa.Param{Type: n.Type, Offset: int32(n.Xoffset)})
		case PPARAMOUT:
			s.decladdrs[n] = s.entryNewValue2A(ssa.OpLocalAddr, types.NewPtr(n.Type), n, s.sp, s.startmem)
			results = append(results, ssa.Param{Type: n.Type, Offset: int32(n.Xoffset)})
			if s.canSSA(n) {
				// Save ssa-able PPARAMOUT variables so we can
				// store them back to the stack at the end of
				// the function.
				s.returns = append(s.returns, n)
			}
		case PAUTO:
			// processed at each use, to prevent Addr coming
			// before the decl.
		case PAUTOHEAP:
			// moved to heap - already handled by frontend
		case PFUNC:
			// local function - already handled by frontend
		default:
			s.Fatalf("local variable with class %v unimplemented", n.Class())
		}
	}

	// Populate SSAable arguments.
	for _, n := range fn.Func.Dcl {
		if n.Class() == PPARAM && s.canSSA(n) {
			v := s.newValue0A(ssa.OpArg, n.Type, n)
			s.vars[n] = v
			s.addNamedValue(n, v) // This helps with debugging information, not needed for compilation itself.
		}
	}

	// Convert the AST-based IR to the SSA-based IR
	s.stmtList(fn.Func.Enter)
	s.stmtList(fn.Nbody)

	// fallthrough to exit
	if s.curBlock != nil {
		s.pushLine(fn.Func.Endlineno)
		s.exit()
		s.popLine()
	}

	for _, b := range s.f.Blocks {
		if b.Pos != src.NoXPos {
			s.updateUnsetPredPos(b)
		}
	}

	s.insertPhis()

	// Main call to ssa package to compile function
	ssa.Compile(s.f)

	if s.hasOpenDefers {
		s.emitOpenDeferInfo()
	}

	return s.f
}

func dumpSourcesColumn(writer *ssa.HTMLWriter, fn *Node) {
	// Read sources of target function fn.
	fname := Ctxt.PosTable.Pos(fn.Pos).Filename()
	targetFn, err := readFuncLines(fname, fn.Pos.Line(), fn.Func.Endlineno.Line())
	if err != nil {
		writer.Logf("cannot read sources for function %v: %v", fn, err)
	}

	// Read sources of inlined functions.
	var inlFns []*ssa.FuncLines
	for _, fi := range ssaDumpInlined {
		var elno src.XPos
		if fi.Name.Defn == nil {
			// Endlineno is filled from exported data.
			elno = fi.Func.Endlineno
		} else {
			elno = fi.Name.Defn.Func.Endlineno
		}
		fname := Ctxt.PosTable.Pos(fi.Pos).Filename()
		fnLines, err := readFuncLines(fname, fi.Pos.Line(), elno.Line())
		if err != nil {
			writer.Logf("cannot read sources for inlined function %v: %v", fi, err)
			continue
		}
		inlFns = append(inlFns, fnLines)
	}

	sort.Sort(ssa.ByTopo(inlFns))
	if targetFn != nil {
		inlFns = append([]*ssa.FuncLines{targetFn}, inlFns...)
	}

	writer.WriteSources("sources", inlFns)
}

func readFuncLines(file string, start, end uint) (*ssa.FuncLines, error) {
	f, err := os.Open(os.ExpandEnv(file))
	if err != nil {
		return nil, err
	}
	defer f.Close()
	var lines []string
	ln := uint(1)
	scanner := bufio.NewScanner(f)
	for scanner.Scan() && ln <= end {
		if ln >= start {
			lines = append(lines, scanner.Text())
		}
		ln++
	}
	return &ssa.FuncLines{Filename: file, StartLineno: start, Lines: lines}, nil
}

// updateUnsetPredPos propagates the earliest-value position information for b
// towards all of b's predecessors that need a position, and recurs on that
// predecessor if its position is updated. B should have a non-empty position.
func (s *state) updateUnsetPredPos(b *ssa.Block) {
	if b.Pos == src.NoXPos {
		s.Fatalf("Block %s should have a position", b)
	}
	bestPos := src.NoXPos
	for _, e := range b.Preds {
		p := e.Block()
		if !p.LackingPos() {
			continue
		}
		if bestPos == src.NoXPos {
			bestPos = b.Pos
			for _, v := range b.Values {
				if v.LackingPos() {
					continue
				}
				if v.Pos != src.NoXPos {
					// Assume values are still in roughly textual order;
					// TODO: could also seek minimum position?
					bestPos = v.Pos
					break
				}
			}
		}
		p.Pos = bestPos
		s.updateUnsetPredPos(p) // We do not expect long chains of these, thus recursion is okay.
	}
}

// Information about each open-coded defer.
type openDeferInfo struct {
	// The ODEFER node representing the function call of the defer
	n *Node
	// If defer call is closure call, the address of the argtmp where the
	// closure is stored.
	closure *ssa.Value
	// The node representing the argtmp where the closure is stored - used for
	// function, method, or interface call, to store a closure that panic
	// processing can use for this defer.
	closureNode *Node
	// If defer call is interface call, the address of the argtmp where the
	// receiver is stored
	rcvr *ssa.Value
	// The node representing the argtmp where the receiver is stored
	rcvrNode *Node
	// The addresses of the argtmps where the evaluated arguments of the defer
	// function call are stored.
	argVals []*ssa.Value
	// The nodes representing the argtmps where the args of the defer are stored
	argNodes []*Node
}

type state struct {
	// configuration (arch) information
	config *ssa.Config

	// function we're building
	f *ssa.Func

	// Node for function
	curfn *Node

	// labels and labeled control flow nodes (OFOR, OFORUNTIL, OSWITCH, OSELECT) in f
	labels       map[string]*ssaLabel
	labeledNodes map[*Node]*ssaLabel

	// unlabeled break and continue statement tracking
	breakTo    *ssa.Block // current target for plain break statement
	continueTo *ssa.Block // current target for plain continue statement

	// current location where we're interpreting the AST
	curBlock *ssa.Block

	// variable assignments in the current block (map from variable symbol to ssa value)
	// *Node is the unique identifier (an ONAME Node) for the variable.
	// TODO: keep a single varnum map, then make all of these maps slices instead?
	vars map[*Node]*ssa.Value

	// fwdVars are variables that are used before they are defined in the current block.
	// This map exists just to coalesce multiple references into a single FwdRef op.
	// *Node is the unique identifier (an ONAME Node) for the variable.
	fwdVars map[*Node]*ssa.Value

	// all defined variables at the end of each block. Indexed by block ID.
	defvars []map[*Node]*ssa.Value

	// addresses of PPARAM and PPARAMOUT variables.
	decladdrs map[*Node]*ssa.Value

	// starting values. Memory, stack pointer, and globals pointer
	startmem *ssa.Value
	sp       *ssa.Value
	sb       *ssa.Value
	// value representing address of where deferBits autotmp is stored
	deferBitsAddr *ssa.Value
	deferBitsTemp *Node

	// line number stack. The current line number is top of stack
	line []src.XPos
	// the last line number processed; it may have been popped
	lastPos src.XPos

	// list of panic calls by function name and line number.
	// Used to deduplicate panic calls.
	panics map[funcLine]*ssa.Block

	// list of PPARAMOUT (return) variables.
	returns []*Node

	cgoUnsafeArgs bool
	hasdefer      bool // whether the function contains a defer statement
	softFloat     bool
	hasOpenDefers bool // whether we are doing open-coded defers

	// If doing open-coded defers, list of info about the defer calls in
	// scanning order. Hence, at exit we should run these defers in reverse
	// order of this list
	openDefers []*openDeferInfo
	// For open-coded defers, this is the beginning and end blocks of the last
	// defer exit code that we have generated so far. We use these to share
	// code between exits if the shareDeferExits option (disabled by default)
	// is on.
	lastDeferExit       *ssa.Block // Entry block of last defer exit code we generated
	lastDeferFinalBlock *ssa.Block // Final block of last defer exit code we generated
	lastDeferCount      int        // Number of defers encountered at that point

	prevCall *ssa.Value // the previous call; use this to tie results to the call op.
}

type funcLine struct {
	f    *obj.LSym
	base *src.PosBase
	line uint
}

type ssaLabel struct {
	target         *ssa.Block // block identified by this label
	breakTarget    *ssa.Block // block to break to in control flow node identified by this label
	continueTarget *ssa.Block // block to continue to in control flow node identified by this label
}

// label returns the label associated with sym, creating it if necessary.
func (s *state) label(sym *types.Sym) *ssaLabel {
	lab := s.labels[sym.Name]
	if lab == nil {
		lab = new(ssaLabel)
		s.labels[sym.Name] = lab
	}
	return lab
}

func (s *state) Logf(msg string, args ...interface{}) { s.f.Logf(msg, args...) }
func (s *state) Log() bool                            { return s.f.Log() }
func (s *state) Fatalf(msg string, args ...interface{}) {
	s.f.Frontend().Fatalf(s.peekPos(), msg, args...)
}
func (s *state) Warnl(pos src.XPos, msg string, args ...interface{}) { s.f.Warnl(pos, msg, args...) }
func (s *state) Debug_checknil() bool                                { return s.f.Frontend().Debug_checknil() }

var (
	// dummy node for the memory variable
	memVar = Node{Op: ONAME, Sym: &types.Sym{Name: "mem"}}

	// dummy nodes for temporary variables
	ptrVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "ptr"}}
	lenVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "len"}}
	newlenVar    = Node{Op: ONAME, Sym: &types.Sym{Name: "newlen"}}
	capVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "cap"}}
	typVar       = Node{Op: ONAME, Sym: &types.Sym{Name: "typ"}}
	okVar        = Node{Op: ONAME, Sym: &types.Sym{Name: "ok"}}
	deferBitsVar = Node{Op: ONAME, Sym: &types.Sym{Name: "deferBits"}}
)

// startBlock sets the current block we're generating code in to b.
func (s *state) startBlock(b *ssa.Block) {
	if s.curBlock != nil {
		s.Fatalf("starting block %v when block %v has not ended", b, s.curBlock)
	}
	s.curBlock = b
	s.vars = map[*Node]*ssa.Value{}
	for n := range s.fwdVars {
		delete(s.fwdVars, n)
	}
}

// endBlock marks the end of generating code for the current block.
// Returns the (former) current block. Returns nil if there is no current
// block, i.e. if no code flows to the current execution point.
func (s *state) endBlock() *ssa.Block {
	b := s.curBlock
	if b == nil {
		return nil
	}
	for len(s.defvars) <= int(b.ID) {
		s.defvars = append(s.defvars, nil)
	}
	s.defvars[b.ID] = s.vars
	s.curBlock = nil
	s.vars = nil
	if b.LackingPos() {
		// Empty plain blocks get the line of their successor (handled after all blocks created),
		// except for increment blocks in For statements (handled in ssa conversion of OFOR),
		// and for blocks ending in GOTO/BREAK/CONTINUE.
		b.Pos = src.NoXPos
	} else {
		b.Pos = s.lastPos
	}
	return b
}

// pushLine pushes a line number on the line number stack.
func (s *state) pushLine(line src.XPos) {
	if !line.IsKnown() {
		// the frontend may emit node with line number missing,
		// use the parent line number in this case.
		line = s.peekPos()
		if Debug.K != 0 {
			Warn("buildssa: unknown position (line 0)")
		}
	} else {
		s.lastPos = line
	}

	s.line = append(s.line, line)
}

// popLine pops the top of the line number stack.
func (s *state) popLine() {
	s.line = s.line[:len(s.line)-1]
}

// peekPos peeks the top of the line number stack.
func (s *state) peekPos() src.XPos {
	return s.line[len(s.line)-1]
}

// newValue0 adds a new value with no arguments to the current block.
func (s *state) newValue0(op ssa.Op, t *types.Type) *ssa.Value {
	return s.curBlock.NewValue0(s.peekPos(), op, t)
}

// newValue0A adds a new value with no arguments and an aux value to the current block.
func (s *state) newValue0A(op ssa.Op, t *types.Type, aux interface{}) *ssa.Value {
	return s.curBlock.NewValue0A(s.peekPos(), op, t, aux)
}

// newValue0I adds a new value with no arguments and an auxint value to the current block.
func (s *state) newValue0I(op ssa.Op, t *types.Type, auxint int64) *ssa.Value {
	return s.curBlock.NewValue0I(s.peekPos(), op, t, auxint)
}

// newValue1 adds a new value with one argument to the current block.
func (s *state) newValue1(op ssa.Op, t *types.Type, arg *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue1(s.peekPos(), op, t, arg)
}

// newValue1A adds a new value with one argument and an aux value to the current block.
func (s *state) newValue1A(op ssa.Op, t *types.Type, aux interface{}, arg *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue1A(s.peekPos(), op, t, aux, arg)
}

// newValue1Apos adds a new value with one argument and an aux value to the current block.
// isStmt determines whether the created values may be a statement or not
// (i.e., false means never, yes means maybe).
func (s *state) newValue1Apos(op ssa.Op, t *types.Type, aux interface{}, arg *ssa.Value, isStmt bool) *ssa.Value {
	if isStmt {
		return s.curBlock.NewValue1A(s.peekPos(), op, t, aux, arg)
	}
	return s.curBlock.NewValue1A(s.peekPos().WithNotStmt(), op, t, aux, arg)
}

// newValue1I adds a new value with one argument and an auxint value to the current block.
func (s *state) newValue1I(op ssa.Op, t *types.Type, aux int64, arg *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue1I(s.peekPos(), op, t, aux, arg)
}

// newValue2 adds a new value with two arguments to the current block.
func (s *state) newValue2(op ssa.Op, t *types.Type, arg0, arg1 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue2(s.peekPos(), op, t, arg0, arg1)
}

// newValue2A adds a new value with two arguments and an aux value to the current block.
func (s *state) newValue2A(op ssa.Op, t *types.Type, aux interface{}, arg0, arg1 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue2A(s.peekPos(), op, t, aux, arg0, arg1)
}

// newValue2Apos adds a new value with two arguments and an aux value to the current block.
// isStmt determines whether the created values may be a statement or not
// (i.e., false means never, yes means maybe).
func (s *state) newValue2Apos(op ssa.Op, t *types.Type, aux interface{}, arg0, arg1 *ssa.Value, isStmt bool) *ssa.Value {
	if isStmt {
		return s.curBlock.NewValue2A(s.peekPos(), op, t, aux, arg0, arg1)
	}
	return s.curBlock.NewValue2A(s.peekPos().WithNotStmt(), op, t, aux, arg0, arg1)
}

// newValue2I adds a new value with two arguments and an auxint value to the current block.
func (s *state) newValue2I(op ssa.Op, t *types.Type, aux int64, arg0, arg1 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue2I(s.peekPos(), op, t, aux, arg0, arg1)
}

// newValue3 adds a new value with three arguments to the current block.
func (s *state) newValue3(op ssa.Op, t *types.Type, arg0, arg1, arg2 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue3(s.peekPos(), op, t, arg0, arg1, arg2)
}

// newValue3I adds a new value with three arguments and an auxint value to the current block.
func (s *state) newValue3I(op ssa.Op, t *types.Type, aux int64, arg0, arg1, arg2 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue3I(s.peekPos(), op, t, aux, arg0, arg1, arg2)
}

// newValue3A adds a new value with three arguments and an aux value to the current block.
func (s *state) newValue3A(op ssa.Op, t *types.Type, aux interface{}, arg0, arg1, arg2 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue3A(s.peekPos(), op, t, aux, arg0, arg1, arg2)
}

// newValue3Apos adds a new value with three arguments and an aux value to the current block.
// isStmt determines whether the created values may be a statement or not
// (i.e., false means never, yes means maybe).
func (s *state) newValue3Apos(op ssa.Op, t *types.Type, aux interface{}, arg0, arg1, arg2 *ssa.Value, isStmt bool) *ssa.Value {
	if isStmt {
		return s.curBlock.NewValue3A(s.peekPos(), op, t, aux, arg0, arg1, arg2)
	}
	return s.curBlock.NewValue3A(s.peekPos().WithNotStmt(), op, t, aux, arg0, arg1, arg2)
}

// newValue4 adds a new value with four arguments to the current block.
func (s *state) newValue4(op ssa.Op, t *types.Type, arg0, arg1, arg2, arg3 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue4(s.peekPos(), op, t, arg0, arg1, arg2, arg3)
}

// newValue4 adds a new value with four arguments and an auxint value to the current block.
func (s *state) newValue4I(op ssa.Op, t *types.Type, aux int64, arg0, arg1, arg2, arg3 *ssa.Value) *ssa.Value {
	return s.curBlock.NewValue4I(s.peekPos(), op, t, aux, arg0, arg1, arg2, arg3)
}

// entryNewValue0 adds a new value with no arguments to the entry block.
func (s *state) entryNewValue0(op ssa.Op, t *types.Type) *ssa.Value {
	return s.f.Entry.NewValue0(src.NoXPos, op, t)
}

// entryNewValue0A adds a new value with no arguments and an aux value to the entry block.
func (s *state) entryNewValue0A(op ssa.Op, t *types.Type, aux interface{}) *ssa.Value {
	return s.f.Entry.NewValue0A(src.NoXPos, op, t, aux)
}

// entryNewValue1 adds a new value with one argument to the entry block.
func (s *state) entryNewValue1(op ssa.Op, t *types.Type, arg *ssa.Value) *ssa.Value {
	return s.f.Entry.NewValue1(src.NoXPos, op, t, arg)
}

// entryNewValue1 adds a new value with one argument and an auxint value to the entry block.
func (s *state) entryNewValue1I(op ssa.Op, t *types.Type, auxint int64, arg *ssa.Value) *ssa.Value {
	return s.f.Entry.NewValue1I(src.NoXPos, op, t, auxint, arg)
}

// entryNewValue1A adds a new value with one argument and an aux value to the entry block.
func (s *state) entryNewValue1A(op ssa.Op, t *types.Type, aux interface{}, arg *ssa.Value) *ssa.Value {
	return s.f.Entry.NewValue1A(src.NoXPos, op, t, aux, arg)
}

// entryNewValue2 adds a new value with two arguments to the entry block.
func (s *state) entryNewValue2(op ssa.Op, t *types.Type, arg0, arg1 *ssa.Value) *ssa.Value {
	return s.f.Entry.NewValue2(src.NoXPos, op, t, arg0, arg1)
}

// entryNewValue2A adds a new value with two arguments and an aux value to the entry block.
func (s *state) entryNewValue2A(op ssa.Op, t *types.Type, aux interface{}, arg0, arg1 *ssa.Value) *ssa.Value {
	return s.f.Entry.NewValue2A(src.NoXPos, op, t, aux, arg0, arg1)
}

// const* routines add a new const value to the entry block.
func (s *state) constSlice(t *types.Type) *ssa.Value {
	return s.f.ConstSlice(t)
}
func (s *state) constInterface(t *types.Type) *ssa.Value {
	return s.f.ConstInterface(t)
}
func (s *state) constNil(t *types.Type) *ssa.Value { return s.f.ConstNil(t) }
func (s *state) constEmptyString(t *types.Type) *ssa.Value {
	return s.f.ConstEmptyString(t)
}
func (s *state) constBool(c bool) *ssa.Value {
	return s.f.ConstBool(types.Types[TBOOL], c)
}
func (s *state) constInt8(t *types.Type, c int8) *ssa.Value {
	return s.f.ConstInt8(t, c)
}
func (s *state) constInt16(t *types.Type, c int16) *ssa.Value {
	return s.f.ConstInt16(t, c)
}
func (s *state) constInt32(t *types.Type, c int32) *ssa.Value {
	return s.f.ConstInt32(t, c)
}
func (s *state) constInt64(t *types.Type, c int64) *ssa.Value {
	return s.f.ConstInt64(t, c)
}
func (s *state) constFloat32(t *types.Type, c float64) *ssa.Value {
	return s.f.ConstFloat32(t, c)
}
func (s *state) constFloat64(t *types.Type, c float64) *ssa.Value {
	return s.f.ConstFloat64(t, c)
}
func (s *state) constInt(t *types.Type, c int64) *ssa.Value {
	if s.config.PtrSize == 8 {
		return s.constInt64(t, c)
	}
	if int64(int32(c)) != c {
		s.Fatalf("integer constant too big %d", c)
	}
	return s.constInt32(t, int32(c))
}
func (s *state) constOffPtrSP(t *types.Type, c int64) *ssa.Value {
	return s.f.ConstOffPtrSP(t, c, s.sp)
}

// newValueOrSfCall* are wrappers around newValue*, which may create a call to a
// soft-float runtime function instead (when emitting soft-float code).
func (s *state) newValueOrSfCall1(op ssa.Op, t *types.Type, arg *ssa.Value) *ssa.Value {
	if s.softFloat {
		if c, ok := s.sfcall(op, arg); ok {
			return c
		}
	}
	return s.newValue1(op, t, arg)
}
func (s *state) newValueOrSfCall2(op ssa.Op, t *types.Type, arg0, arg1 *ssa.Value) *ssa.Value {
	if s.softFloat {
		if c, ok := s.sfcall(op, arg0, arg1); ok {
			return c
		}
	}
	return s.newValue2(op, t, arg0, arg1)
}

type instrumentKind uint8

const (
	instrumentRead = iota
	instrumentWrite
	instrumentMove
)

func (s *state) instrument(t *types.Type, addr *ssa.Value, kind instrumentKind) {
	s.instrument2(t, addr, nil, kind)
}

// instrumentFields instruments a read/write operation on addr.
// If it is instrumenting for MSAN and t is a struct type, it instruments
// operation for each field, instead of for the whole struct.
func (s *state) instrumentFields(t *types.Type, addr *ssa.Value, kind instrumentKind) {
	if !flag_msan || !t.IsStruct() {
		s.instrument(t, addr, kind)
		return
	}
	for _, f := range t.Fields().Slice() {
		if f.Sym.IsBlank() {
			continue
		}
		offptr := s.newValue1I(ssa.OpOffPtr, types.NewPtr(f.Type), f.Offset, addr)
		s.instrumentFields(f.Type, offptr, kind)
	}
}

func (s *state) instrumentMove(t *types.Type, dst, src *ssa.Value) {
	if flag_msan {
		s.instrument2(t, dst, src, instrumentMove)
	} else {
		s.instrument(t, src, instrumentRead)
		s.instrument(t, dst, instrumentWrite)
	}
}

func (s *state) instrument2(t *types.Type, addr, addr2 *ssa.Value, kind instrumentKind) {
	if !s.curfn.Func.InstrumentBody() {
		return
	}

	w := t.Size()
	if w == 0 {
		return // can't race on zero-sized things
	}

	if ssa.IsSanitizerSafeAddr(addr) {
		return
	}

	var fn *obj.LSym
	needWidth := false

	if addr2 != nil && kind != instrumentMove {
		panic("instrument2: non-nil addr2 for non-move instrumentation")
	}

	if flag_msan {
		switch kind {
		case instrumentRead:
			fn = msanread
		case instrumentWrite:
			fn = msanwrite
		case instrumentMove:
			fn = msanmove
		default:
			panic("unreachable")
		}
		needWidth = true
	} else if flag_race && t.NumComponents(types.CountBlankFields) > 1 {
		// for composite objects we have to write every address
		// because a write might happen to any subobject.
		// composites with only one element don't have subobjects, though.
		switch kind {
		case instrumentRead:
			fn = racereadrange
		case instrumentWrite:
			fn = racewriterange
		default:
			panic("unreachable")
		}
		needWidth = true
	} else if flag_race {
		// for non-composite objects we can write just the start
		// address, as any write must write the first byte.
		switch kind {
		case instrumentRead:
			fn = raceread
		case instrumentWrite:
			fn = racewrite
		default:
			panic("unreachable")
		}
	} else {
		panic("unreachable")
	}

	args := []*ssa.Value{addr}
	if addr2 != nil {
		args = append(args, addr2)
	}
	if needWidth {
		args = append(args, s.constInt(types.Types[TUINTPTR], w))
	}
	s.rtcall(fn, true, nil, args...)
}

func (s *state) load(t *types.Type, src *ssa.Value) *ssa.Value {
	s.instrumentFields(t, src, instrumentRead)
	return s.rawLoad(t, src)
}

func (s *state) rawLoad(t *types.Type, src *ssa.Value) *ssa.Value {
	return s.newValue2(ssa.OpLoad, t, src, s.mem())
}

func (s *state) store(t *types.Type, dst, val *ssa.Value) {
	s.vars[&memVar] = s.newValue3A(ssa.OpStore, types.TypeMem, t, dst, val, s.mem())
}

func (s *state) zero(t *types.Type, dst *ssa.Value) {
	s.instrument(t, dst, instrumentWrite)
	store := s.newValue2I(ssa.OpZero, types.TypeMem, t.Size(), dst, s.mem())
	store.Aux = t
	s.vars[&memVar] = store
}

func (s *state) move(t *types.Type, dst, src *ssa.Value) {
	s.instrumentMove(t, dst, src)
	store := s.newValue3I(ssa.OpMove, types.TypeMem, t.Size(), dst, src, s.mem())
	store.Aux = t
	s.vars[&memVar] = store
}

// stmtList converts the statement list n to SSA and adds it to s.
func (s *state) stmtList(l Nodes) {
	for _, n := range l.Slice() {
		s.stmt(n)
	}
}

// stmt converts the statement n to SSA and adds it to s.
func (s *state) stmt(n *Node) {
	if !(n.Op == OVARKILL || n.Op == OVARLIVE || n.Op == OVARDEF) {
		// OVARKILL, OVARLIVE, and OVARDEF are invisible to the programmer, so we don't use their line numbers to avoid confusion in debugging.
		s.pushLine(n.Pos)
		defer s.popLine()
	}

	// If s.curBlock is nil, and n isn't a label (which might have an associated goto somewhere),
	// then this code is dead. Stop here.
	if s.curBlock == nil && n.Op != OLABEL {
		return
	}

	s.stmtList(n.Ninit)
	switch n.Op {

	case OBLOCK:
		s.stmtList(n.List)

	// No-ops
	case OEMPTY, ODCLCONST, ODCLTYPE, OFALL:

	// Expression statements
	case OCALLFUNC:
		if isIntrinsicCall(n) {
			s.intrinsicCall(n)
			return
		}
		fallthrough

	case OCALLMETH, OCALLINTER:
		s.callResult(n, callNormal)
		if n.Op == OCALLFUNC && n.Left.Op == ONAME && n.Left.Class() == PFUNC {
			if fn := n.Left.Sym.Name; compiling_runtime && fn == "throw" ||
				n.Left.Sym.Pkg == Runtimepkg && (fn == "throwinit" || fn == "gopanic" || fn == "panicwrap" || fn == "block" || fn == "panicmakeslicelen" || fn == "panicmakeslicecap") {
				m := s.mem()
				b := s.endBlock()
				b.Kind = ssa.BlockExit
				b.SetControl(m)
				// TODO: never rewrite OPANIC to OCALLFUNC in the
				// first place. Need to wait until all backends
				// go through SSA.
			}
		}
	case ODEFER:
		if Debug_defer > 0 {
			var defertype string
			if s.hasOpenDefers {
				defertype = "open-coded"
			} else if n.Esc == EscNever {
				defertype = "stack-allocated"
			} else {
				defertype = "heap-allocated"
			}
			Warnl(n.Pos, "%s defer", defertype)
		}
		if s.hasOpenDefers {
			s.openDeferRecord(n.Left)
		} else {
			d := callDefer
			if n.Esc == EscNever {
				d = callDeferStack
			}
			s.callResult(n.Left, d)
		}
	case OGO:
		s.callResult(n.Left, callGo)

	case OAS2DOTTYPE:
		res, resok := s.dottype(n.Right, true)
		deref := false
		if !canSSAType(n.Right.Type) {
			if res.Op != ssa.OpLoad {
				s.Fatalf("dottype of non-load")
			}
			mem := s.mem()
			if mem.Op == ssa.OpVarKill {
				mem = mem.Args[0]
			}
			if res.Args[1] != mem {
				s.Fatalf("memory no longer live from 2-result dottype load")
			}
			deref = true
			res = res.Args[0]
		}
		s.assign(n.List.First(), res, deref, 0)
		s.assign(n.List.Second(), resok, false, 0)
		return

	case OAS2FUNC:
		// We come here only when it is an intrinsic call returning two values.
		if !isIntrinsicCall(n.Right) {
			s.Fatalf("non-intrinsic AS2FUNC not expanded %v", n.Right)
		}
		v := s.intrinsicCall(n.Right)
		v1 := s.newValue1(ssa.OpSelect0, n.List.First().Type, v)
		v2 := s.newValue1(ssa.OpSelect1, n.List.Second().Type, v)
		s.assign(n.List.First(), v1, false, 0)
		s.assign(n.List.Second(), v2, false, 0)
		return

	case ODCL:
		if n.Left.Class() == PAUTOHEAP {
			s.Fatalf("DCL %v", n)
		}

	case OLABEL:
		sym := n.Sym
		lab := s.label(sym)

		// Associate label with its control flow node, if any
		if ctl := n.labeledControl(); ctl != nil {
			s.labeledNodes[ctl] = lab
		}

		// The label might already have a target block via a goto.
		if lab.target == nil {
			lab.target = s.f.NewBlock(ssa.BlockPlain)
		}

		// Go to that label.
		// (We pretend "label:" is preceded by "goto label", unless the predecessor is unreachable.)
		if s.curBlock != nil {
			b := s.endBlock()
			b.AddEdgeTo(lab.target)
		}
		s.startBlock(lab.target)

	case OGOTO:
		sym := n.Sym

		lab := s.label(sym)
		if lab.target == nil {
			lab.target = s.f.NewBlock(ssa.BlockPlain)
		}

		b := s.endBlock()
		b.Pos = s.lastPos.WithIsStmt() // Do this even if b is an empty block.
		b.AddEdgeTo(lab.target)

	case OAS:
		if n.Left == n.Right && n.Left.Op == ONAME {
			// An x=x assignment. No point in doing anything
			// here. In addition, skipping this assignment
			// prevents generating:
			//   VARDEF x
			//   COPY x -> x
			// which is bad because x is incorrectly considered
			// dead before the vardef. See issue #14904.
			return
		}

		// Evaluate RHS.
		rhs := n.Right
		if rhs != nil {
			switch rhs.Op {
			case OSTRUCTLIT, OARRAYLIT, OSLICELIT:
				// All literals with nonzero fields have already been
				// rewritten during walk. Any that remain are just T{}
				// or equivalents. Use the zero value.
				if !isZero(rhs) {
					s.Fatalf("literal with nonzero value in SSA: %v", rhs)
				}
				rhs = nil
			case OAPPEND:
				// Check whether we're writing the result of an append back to the same slice.
				// If so, we handle it specially to avoid write barriers on the fast
				// (non-growth) path.
				if !samesafeexpr(n.Left, rhs.List.First()) || Debug.N != 0 {
					break
				}
				// If the slice can be SSA'd, it'll be on the stack,
				// so there will be no write barriers,
				// so there's no need to attempt to prevent them.
				if s.canSSA(n.Left) {
					if Debug_append > 0 { // replicating old diagnostic message
						Warnl(n.Pos, "append: len-only update (in local slice)")
					}
					break
				}
				if Debug_append > 0 {
					Warnl(n.Pos, "append: len-only update")
				}
				s.append(rhs, true)
				return
			}
		}

		if n.Left.isBlank() {
			// _ = rhs
			// Just evaluate rhs for side-effects.
			if rhs != nil {
				s.expr(rhs)
			}
			return
		}

		var t *types.Type
		if n.Right != nil {
			t = n.Right.Type
		} else {
			t = n.Left.Type
		}

		var r *ssa.Value
		deref := !canSSAType(t)
		if deref {
			if rhs == nil {
				r = nil // Signal assign to use OpZero.
			} else {
				r = s.addr(rhs)
			}
		} else {
			if rhs == nil {
				r = s.zeroVal(t)
			} else {
				r = s.expr(rhs)
			}
		}

		var skip skipMask
		if rhs != nil && (rhs.Op == OSLICE || rhs.Op == OSLICE3 || rhs.Op == OSLICESTR) && samesafeexpr(rhs.Left, n.Left) {
			// We're assigning a slicing operation back to its source.
			// Don't write back fields we aren't changing. See issue #14855.
			i, j, k := rhs.SliceBounds()
			if i != nil && (i.Op == OLITERAL && i.Val().Ctype() == CTINT && i.Int64Val() == 0) {
				// [0:...] is the same as [:...]
				i = nil
			}
			// TODO: detect defaults for len/cap also.
			// Currently doesn't really work because (*p)[:len(*p)] appears here as:
			//    tmp = len(*p)
			//    (*p)[:tmp]
			//if j != nil && (j.Op == OLEN && samesafeexpr(j.Left, n.Left)) {
			//      j = nil
			//}
			//if k != nil && (k.Op == OCAP && samesafeexpr(k.Left, n.Left)) {
			//      k = nil
			//}
			if i == nil {
				skip |= skipPtr
				if j == nil {
					skip |= skipLen
				}
				if k == nil {
					skip |= skipCap
				}
			}
		}

		s.assign(n.Left, r, deref, skip)

	case OIF:
		if Isconst(n.Left, CTBOOL) {
			s.stmtList(n.Left.Ninit)
			if n.Left.BoolVal() {
				s.stmtList(n.Nbody)
			} else {
				s.stmtList(n.Rlist)
			}
			break
		}

		bEnd := s.f.NewBlock(ssa.BlockPlain)
		var likely int8
		if n.Likely() {
			likely = 1
		}
		var bThen *ssa.Block
		if n.Nbody.Len() != 0 {
			bThen = s.f.NewBlock(ssa.BlockPlain)
		} else {
			bThen = bEnd
		}
		var bElse *ssa.Block
		if n.Rlist.Len() != 0 {
			bElse = s.f.NewBlock(ssa.BlockPlain)
		} else {
			bElse = bEnd
		}
		s.condBranch(n.Left, bThen, bElse, likely)

		if n.Nbody.Len() != 0 {
			s.startBlock(bThen)
			s.stmtList(n.Nbody)
			if b := s.endBlock(); b != nil {
				b.AddEdgeTo(bEnd)
			}
		}
		if n.Rlist.Len() != 0 {
			s.startBlock(bElse)
			s.stmtList(n.Rlist)
			if b := s.endBlock(); b != nil {
				b.AddEdgeTo(bEnd)
			}
		}
		s.startBlock(bEnd)

	case ORETURN:
		s.stmtList(n.List)
		b := s.exit()
		b.Pos = s.lastPos.WithIsStmt()

	case ORETJMP:
		s.stmtList(n.List)
		b := s.exit()
		b.Kind = ssa.BlockRetJmp // override BlockRet
		b.Aux = n.Sym.Linksym()

	case OCONTINUE, OBREAK:
		var to *ssa.Block
		if n.Sym == nil {
			// plain break/continue
			switch n.Op {
			case OCONTINUE:
				to = s.continueTo
			case OBREAK:
				to = s.breakTo
			}
		} else {
			// labeled break/continue; look up the target
			sym := n.Sym
			lab := s.label(sym)
			switch n.Op {
			case OCONTINUE:
				to = lab.continueTarget
			case OBREAK:
				to = lab.breakTarget
			}
		}

		b := s.endBlock()
		b.Pos = s.lastPos.WithIsStmt() // Do this even if b is an empty block.
		b.AddEdgeTo(to)

	case OFOR, OFORUNTIL:
		// OFOR: for Ninit; Left; Right { Nbody }
		// cond (Left); body (Nbody); incr (Right)
		//
		// OFORUNTIL: for Ninit; Left; Right; List { Nbody }
		// => body: { Nbody }; incr: Right; if Left { lateincr: List; goto body }; end:
		bCond := s.f.NewBlock(ssa.BlockPlain)
		bBody := s.f.NewBlock(ssa.BlockPlain)
		bIncr := s.f.NewBlock(ssa.BlockPlain)
		bEnd := s.f.NewBlock(ssa.BlockPlain)

		// ensure empty for loops have correct position; issue #30167
		bBody.Pos = n.Pos

		// first, jump to condition test (OFOR) or body (OFORUNTIL)
		b := s.endBlock()
		if n.Op == OFOR {
			b.AddEdgeTo(bCond)
			// generate code to test condition
			s.startBlock(bCond)
			if n.Left != nil {
				s.condBranch(n.Left, bBody, bEnd, 1)
			} else {
				b := s.endBlock()
				b.Kind = ssa.BlockPlain
				b.AddEdgeTo(bBody)
			}

		} else {
			b.AddEdgeTo(bBody)
		}

		// set up for continue/break in body
		prevContinue := s.continueTo
		prevBreak := s.breakTo
		s.continueTo = bIncr
		s.breakTo = bEnd
		lab := s.labeledNodes[n]
		if lab != nil {
			// labeled for loop
			lab.continueTarget = bIncr
			lab.breakTarget = bEnd
		}

		// generate body
		s.startBlock(bBody)
		s.stmtList(n.Nbody)

		// tear down continue/break
		s.continueTo = prevContinue
		s.breakTo = prevBreak
		if lab != nil {
			lab.continueTarget = nil
			lab.breakTarget = nil
		}

		// done with body, goto incr
		if b := s.endBlock(); b != nil {
			b.AddEdgeTo(bIncr)
		}

		// generate incr (and, for OFORUNTIL, condition)
		s.startBlock(bIncr)
		if n.Right != nil {
			s.stmt(n.Right)
		}
		if n.Op == OFOR {
			if b := s.endBlock(); b != nil {
				b.AddEdgeTo(bCond)
				// It can happen that bIncr ends in a block containing only VARKILL,
				// and that muddles the debugging experience.
				if n.Op != OFORUNTIL && b.Pos == src.NoXPos {
					b.Pos = bCond.Pos
				}
			}
		} else {
			// bCond is unused in OFORUNTIL, so repurpose it.
			bLateIncr := bCond
			// test condition
			s.condBranch(n.Left, bLateIncr, bEnd, 1)
			// generate late increment
			s.startBlock(bLateIncr)
			s.stmtList(n.List)
			s.endBlock().AddEdgeTo(bBody)
		}

		s.startBlock(bEnd)

	case OSWITCH, OSELECT:
		// These have been mostly rewritten by the front end into their Nbody fields.
		// Our main task is to correctly hook up any break statements.
		bEnd := s.f.NewBlock(ssa.BlockPlain)

		prevBreak := s.breakTo
		s.breakTo = bEnd
		lab := s.labeledNodes[n]
		if lab != nil {
			// labeled
			lab.breakTarget = bEnd
		}

		// generate body code
		s.stmtList(n.Nbody)

		s.breakTo = prevBreak
		if lab != nil {
			lab.breakTarget = nil
		}

		// walk adds explicit OBREAK nodes to the end of all reachable code paths.
		// If we still have a current block here, then mark it unreachable.
		if s.curBlock != nil {
			m := s.mem()
			b := s.endBlock()
			b.Kind = ssa.BlockExit
			b.SetControl(m)
		}
		s.startBlock(bEnd)

	case OVARDEF:
		if !s.canSSA(n.Left) {
			s.vars[&memVar] = s.newValue1Apos(ssa.OpVarDef, types.TypeMem, n.Left, s.mem(), false)
		}
	case OVARKILL:
		// Insert a varkill op to record that a variable is no longer live.
		// We only care about liveness info at call sites, so putting the
		// varkill in the store chain is enough to keep it correctly ordered
		// with respect to call ops.
		if !s.canSSA(n.Left) {
			s.vars[&memVar] = s.newValue1Apos(ssa.OpVarKill, types.TypeMem, n.Left, s.mem(), false)
		}

	case OVARLIVE:
		// Insert a varlive op to record that a variable is still live.
		if !n.Left.Name.Addrtaken() {
			s.Fatalf("VARLIVE variable %v must have Addrtaken set", n.Left)
		}
		switch n.Left.Class() {
		case PAUTO, PPARAM, PPARAMOUT:
		default:
			s.Fatalf("VARLIVE variable %v must be Auto or Arg", n.Left)
		}
		s.vars[&memVar] = s.newValue1A(ssa.OpVarLive, types.TypeMem, n.Left, s.mem())

	case OCHECKNIL:
		p := s.expr(n.Left)
		s.nilCheck(p)

	case OINLMARK:
		s.newValue1I(ssa.OpInlMark, types.TypeVoid, n.Xoffset, s.mem())

	default:
		s.Fatalf("unhandled stmt %v", n.Op)
	}
}

// If true, share as many open-coded defer exits as possible (with the downside of
// worse line-number information)
const shareDeferExits = false

// exit processes any code that needs to be generated just before returning.
// It returns a BlockRet block that ends the control flow. Its control value
// will be set to the final memory state.
func (s *state) exit() *ssa.Block {
	if s.hasdefer {
		if s.hasOpenDefers {
			if shareDeferExits && s.lastDeferExit != nil && len(s.openDefers) == s.lastDeferCount {
				if s.curBlock.Kind != ssa.BlockPlain {
					panic("Block for an exit should be BlockPlain")
				}
				s.curBlock.AddEdgeTo(s.lastDeferExit)
				s.endBlock()
				return s.lastDeferFinalBlock
			}
			s.openDeferExit()
		} else {
			s.rtcall(Deferreturn, true, nil)
		}
	}

	// Run exit code. Typically, this code copies heap-allocated PPARAMOUT
	// variables back to the stack.
	s.stmtList(s.curfn.Func.Exit)

	// Store SSAable PPARAMOUT variables back to stack locations.
	for _, n := range s.returns {
		addr := s.decladdrs[n]
		val := s.variable(n, n.Type)
		s.vars[&memVar] = s.newValue1A(ssa.OpVarDef, types.TypeMem, n, s.mem())
		s.store(n.Type, addr, val)
		// TODO: if val is ever spilled, we'd like to use the
		// PPARAMOUT slot for spilling it. That won't happen
		// currently.
	}

	// Do actual return.
	m := s.mem()
	b := s.endBlock()
	b.Kind = ssa.BlockRet
	b.SetControl(m)
	if s.hasdefer && s.hasOpenDefers {
		s.lastDeferFinalBlock = b
	}
	return b
}

type opAndType struct {
	op    Op
	etype types.EType
}

var opToSSA = map[opAndType]ssa.Op{
	opAndType{OADD, TINT8}:    ssa.OpAdd8,
	opAndType{OADD, TUINT8}:   ssa.OpAdd8,
	opAndType{OADD, TINT16}:   ssa.OpAdd16,
	opAndType{OADD, TUINT16}:  ssa.OpAdd16,
	opAndType{OADD, TINT32}:   ssa.OpAdd32,
	opAndType{OADD, TUINT32}:  ssa.OpAdd32,
	opAndType{OADD, TINT64}:   ssa.OpAdd64,
	opAndType{OADD, TUINT64}:  ssa.OpAdd64,
	opAndType{OADD, TFLOAT32}: ssa.OpAdd32F,
	opAndType{OADD, TFLOAT64}: ssa.OpAdd64F,

	opAndType{OSUB, TINT8}:    ssa.OpSub8,
	opAndType{OSUB, TUINT8}:   ssa.OpSub8,
	opAndType{OSUB, TINT16}:   ssa.OpSub16,
	opAndType{OSUB, TUINT16}:  ssa.OpSub16,
	opAndType{OSUB, TINT32}:   ssa.OpSub32,
	opAndType{OSUB, TUINT32}:  ssa.OpSub32,
	opAndType{OSUB, TINT64}:   ssa.OpSub64,
	opAndType{OSUB, TUINT64}:  ssa.OpSub64,
	opAndType{OSUB, TFLOAT32}: ssa.OpSub32F,
	opAndType{OSUB, TFLOAT64}: ssa.OpSub64F,

	opAndType{ONOT, TBOOL}: ssa.OpNot,

	opAndType{ONEG, TINT8}:    ssa.OpNeg8,
	opAndType{ONEG, TUINT8}:   ssa.OpNeg8,
	opAndType{ONEG, TINT16}:   ssa.OpNeg16,
	opAndType{ONEG, TUINT16}:  ssa.OpNeg16,
	opAndType{ONEG, TINT32}:   ssa.OpNeg32,
	opAndType{ONEG, TUINT32}:  ssa.OpNeg32,
	opAndType{ONEG, TINT64}:   ssa.OpNeg64,
	opAndType{ONEG, TUINT64}:  ssa.OpNeg64,
	opAndType{ONEG, TFLOAT32}: ssa.OpNeg32F,
	opAndType{ONEG, TFLOAT64}: ssa.OpNeg64F,

	opAndType{OBITNOT, TINT8}:   ssa.OpCom8,
	opAndType{OBITNOT, TUINT8}:  ssa.OpCom8,
	opAndType{OBITNOT, TINT16}:  ssa.OpCom16,
	opAndType{OBITNOT, TUINT16}: ssa.OpCom16,
	opAndType{OBITNOT, TINT32}:  ssa.OpCom32,
	opAndType{OBITNOT, TUINT32}: ssa.OpCom32,
	opAndType{OBITNOT, TINT64}:  ssa.OpCom64,
	opAndType{OBITNOT, TUINT64}: ssa.OpCom64,

	opAndType{OIMAG, TCOMPLEX64}:  ssa.OpComplexImag,
	opAndType{OIMAG, TCOMPLEX128}: ssa.OpComplexImag,
	opAndType{OREAL, TCOMPLEX64}:  ssa.OpComplexReal,
	opAndType{OREAL, TCOMPLEX128}: ssa.OpComplexReal,

	opAndType{OMUL, TINT8}:    ssa.OpMul8,
	opAndType{OMUL, TUINT8}:   ssa.OpMul8,
	opAndType{OMUL, TINT16}:   ssa.OpMul16,
	opAndType{OMUL, TUINT16}:  ssa.OpMul16,
	opAndType{OMUL, TINT32}:   ssa.OpMul32,
	opAndType{OMUL, TUINT32}:  ssa.OpMul32,
	opAndType{OMUL, TINT64}:   ssa.OpMul64,
	opAndType{OMUL, TUINT64}:  ssa.OpMul64,
	opAndType{OMUL, TFLOAT32}: ssa.OpMul32F,
	opAndType{OMUL, TFLOAT64}: ssa.OpMul64F,

	opAndType{ODIV, TFLOAT32}: ssa.OpDiv32F,
	opAndType{ODIV, TFLOAT64}: ssa.OpDiv64F,

	opAndType{ODIV, TINT8}:   ssa.OpDiv8,
	opAndType{ODIV, TUINT8}:  ssa.OpDiv8u,
	opAndType{ODIV, TINT16}:  ssa.OpDiv16,
	opAndType{ODIV, TUINT16}: ssa.OpDiv16u,
	opAndType{ODIV, TINT32}:  ssa.OpDiv32,
	opAndType{ODIV, TUINT32}: ssa.OpDiv32u,
	opAndType{ODIV, TINT64}:  ssa.OpDiv64,
	opAndType{ODIV, TUINT64}: ssa.OpDiv64u,

	opAndType{OMOD, TINT8}:   ssa.OpMod8,
	opAndType{OMOD, TUINT8}:  ssa.OpMod8u,
	opAndType{OMOD, TINT16}:  ssa.OpMod16,
	opAndType{OMOD, TUINT16}: ssa.OpMod16u,
	opAndType{OMOD, TINT32}:  ssa.OpMod32,
	opAndType{OMOD, TUINT32}: ssa.OpMod32u,
	opAndType{OMOD, TINT64}:  ssa.OpMod64,
	opAndType{OMOD, TUINT64}: ssa.OpMod64u,

	opAndType{OAND, TINT8}:   ssa.OpAnd8,
	opAndType{OAND, TUINT8}:  ssa.OpAnd8,
	opAndType{OAND, TINT16}:  ssa.OpAnd16,
	opAndType{OAND, TUINT16}: ssa.OpAnd16,
	opAndType{OAND, TINT32}:  ssa.OpAnd32,
	opAndType{OAND, TUINT32}: ssa.OpAnd32,
	opAndType{OAND, TINT64}:  ssa.OpAnd64,
	opAndType{OAND, TUINT64}: ssa.OpAnd64,

	opAndType{OOR, TINT8}:   ssa.OpOr8,
	opAndType{OOR, TUINT8}:  ssa.OpOr8,
	opAndType{OOR, TINT16}:  ssa.OpOr16,
	opAndType{OOR, TUINT16}: ssa.OpOr16,
	opAndType{OOR, TINT32}:  ssa.OpOr32,
	opAndType{OOR, TUINT32}: ssa.OpOr32,
	opAndType{OOR, TINT64}:  ssa.OpOr64,
	opAndType{OOR, TUINT64}: ssa.OpOr64,

	opAndType{OXOR, TINT8}:   ssa.OpXor8,
	opAndType{OXOR, TUINT8}:  ssa.OpXor8,
	opAndType{OXOR, TINT16}:  ssa.OpXor16,
	opAndType{OXOR, TUINT16}: ssa.OpXor16,
	opAndType{OXOR, TINT32}:  ssa.OpXor32,
	opAndType{OXOR, TUINT32}: ssa.OpXor32,
	opAndType{OXOR, TINT64}:  ssa.OpXor64,
	opAndType{OXOR, TUINT64}: ssa.OpXor64,

	opAndType{OEQ, TBOOL}:      ssa.OpEqB,
	opAndType{OEQ, TINT8}:      ssa.OpEq8,
	opAndType{OEQ, TUINT8}:     ssa.OpEq8,
	opAndType{OEQ, TINT16}:     ssa.OpEq16,
	opAndType{OEQ, TUINT16}:    ssa.OpEq16,
	opAndType{OEQ, TINT32}:     ssa.OpEq32,
	opAndType{OEQ, TUINT32}:    ssa.OpEq32,
	opAndType{OEQ, TINT64}:     ssa.OpEq64,
	opAndType{OEQ, TUINT64}:    ssa.OpEq64,
	opAndType{OEQ, TINTER}:     ssa.OpEqInter,
	opAndType{OEQ, TSLICE}:     ssa.OpEqSlice,
	opAndType{OEQ, TFUNC}:      ssa.OpEqPtr,
	opAndType{OEQ, TMAP}:       ssa.OpEqPtr,
	opAndType{OEQ, TCHAN}:      ssa.OpEqPtr,
	opAndType{OEQ, TPTR}:       ssa.OpEqPtr,
	opAndType{OEQ, TUINTPTR}:   ssa.OpEqPtr,
	opAndType{OEQ, TUNSAFEPTR}: ssa.OpEqPtr,
	opAndType{OEQ, TFLOAT64}:   ssa.OpEq64F,
	opAndType{OEQ, TFLOAT32}:   ssa.OpEq32F,

	opAndType{ONE, TBOOL}:      ssa.OpNeqB,
	opAndType{ONE, TINT8}:      ssa.OpNeq8,
	opAndType{ONE, TUINT8}:     ssa.OpNeq8,
	opAndType{ONE, TINT16}:     ssa.OpNeq16,
	opAndType{ONE, TUINT16}:    ssa.OpNeq16,
	opAndType{ONE, TINT32}:     ssa.OpNeq32,
	opAndType{ONE, TUINT32}:    ssa.OpNeq32,
	opAndType{ONE, TINT64}:     ssa.OpNeq64,
	opAndType{ONE, TUINT64}:    ssa.OpNeq64,
	opAndType{ONE, TINTER}:     ssa.OpNeqInter,
	opAndType{ONE, TSLICE}:     ssa.OpNeqSlice,
	opAndType{ONE, TFUNC}:      ssa.OpNeqPtr,
	opAndType{ONE, TMAP}:       ssa.OpNeqPtr,
	opAndType{ONE, TCHAN}:      ssa.OpNeqPtr,
	opAndType{ONE, TPTR}:       ssa.OpNeqPtr,
	opAndType{ONE, TUINTPTR}:   ssa.OpNeqPtr,
	opAndType{ONE, TUNSAFEPTR}: ssa.OpNeqPtr,
	opAndType{ONE, TFLOAT64}:   ssa.OpNeq64F,
	opAndType{ONE, TFLOAT32}:   ssa.OpNeq32F,

	opAndType{OLT, TINT8}:    ssa.OpLess8,
	opAndType{OLT, TUINT8}:   ssa.OpLess8U,
	opAndType{OLT, TINT16}:   ssa.OpLess16,
	opAndType{OLT, TUINT16}:  ssa.OpLess16U,
	opAndType{OLT, TINT32}:   ssa.OpLess32,
	opAndType{OLT, TUINT32}:  ssa.OpLess32U,
	opAndType{OLT, TINT64}:   ssa.OpLess64,
	opAndType{OLT, TUINT64}:  ssa.OpLess64U,
	opAndType{OLT, TFLOAT64}: ssa.OpLess64F,
	opAndType{OLT, TFLOAT32}: ssa.OpLess32F,

	opAndType{OLE, TINT8}:    ssa.OpLeq8,
	opAndType{OLE, TUINT8}:   ssa.OpLeq8U,
	opAndType{OLE, TINT16}:   ssa.OpLeq16,
	opAndType{OLE, TUINT16}:  ssa.OpLeq16U,
	opAndType{OLE, TINT32}:   ssa.OpLeq32,
	opAndType{OLE, TUINT32}:  ssa.OpLeq32U,
	opAndType{OLE, TINT64}:   ssa.OpLeq64,
	opAndType{OLE, TUINT64}:  ssa.OpLeq64U,
	opAndType{OLE, TFLOAT64}: ssa.OpLeq64F,
	opAndType{OLE, TFLOAT32}: ssa.OpLeq32F,
}

func (s *state) concreteEtype(t *types.Type) types.EType {
	e := t.Etype
	switch e {
	default:
		return e
	case TINT:
		if s.config.PtrSize == 8 {
			return TINT64
		}
		return TINT32
	case TUINT:
		if s.config.PtrSize == 8 {
			return TUINT64
		}
		return TUINT32
	case TUINTPTR:
		if s.config.PtrSize == 8 {
			return TUINT64
		}
		return TUINT32
	}
}

func (s *state) ssaOp(op Op, t *types.Type) ssa.Op {
	etype := s.concreteEtype(t)
	x, ok := opToSSA[opAndType{op, etype}]
	if !ok {
		s.Fatalf("unhandled binary op %v %s", op, etype)
	}
	return x
}

func floatForComplex(t *types.Type) *types.Type {
	switch t.Etype {
	case TCOMPLEX64:
		return types.Types[TFLOAT32]
	case TCOMPLEX128:
		return types.Types[TFLOAT64]
	}
	Fatalf("unexpected type: %v", t)
	return nil
}

func complexForFloat(t *types.Type) *types.Type {
	switch t.Etype {
	case TFLOAT32:
		return types.Types[TCOMPLEX64]
	case TFLOAT64:
		return types.Types[TCOMPLEX128]
	}
	Fatalf("unexpected type: %v", t)
	return nil
}

type opAndTwoTypes struct {
	op     Op
	etype1 types.EType
	etype2 types.EType
}

type twoTypes struct {
	etype1 types.EType
	etype2 types.EType
}

type twoOpsAndType struct {
	op1              ssa.Op
	op2              ssa.Op
	intermediateType types.EType
}

var fpConvOpToSSA = map[twoTypes]twoOpsAndType{

	twoTypes{TINT8, TFLOAT32}:  twoOpsAndType{ssa.OpSignExt8to32, ssa.OpCvt32to32F, TINT32},
	twoTypes{TINT16, TFLOAT32}: twoOpsAndType{ssa.OpSignExt16to32, ssa.OpCvt32to32F, TINT32},
	twoTypes{TINT32, TFLOAT32}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt32to32F, TINT32},
	twoTypes{TINT64, TFLOAT32}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt64to32F, TINT64},

	twoTypes{TINT8, TFLOAT64}:  twoOpsAndType{ssa.OpSignExt8to32, ssa.OpCvt32to64F, TINT32},
	twoTypes{TINT16, TFLOAT64}: twoOpsAndType{ssa.OpSignExt16to32, ssa.OpCvt32to64F, TINT32},
	twoTypes{TINT32, TFLOAT64}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt32to64F, TINT32},
	twoTypes{TINT64, TFLOAT64}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt64to64F, TINT64},

	twoTypes{TFLOAT32, TINT8}:  twoOpsAndType{ssa.OpCvt32Fto32, ssa.OpTrunc32to8, TINT32},
	twoTypes{TFLOAT32, TINT16}: twoOpsAndType{ssa.OpCvt32Fto32, ssa.OpTrunc32to16, TINT32},
	twoTypes{TFLOAT32, TINT32}: twoOpsAndType{ssa.OpCvt32Fto32, ssa.OpCopy, TINT32},
	twoTypes{TFLOAT32, TINT64}: twoOpsAndType{ssa.OpCvt32Fto64, ssa.OpCopy, TINT64},

	twoTypes{TFLOAT64, TINT8}:  twoOpsAndType{ssa.OpCvt64Fto32, ssa.OpTrunc32to8, TINT32},
	twoTypes{TFLOAT64, TINT16}: twoOpsAndType{ssa.OpCvt64Fto32, ssa.OpTrunc32to16, TINT32},
	twoTypes{TFLOAT64, TINT32}: twoOpsAndType{ssa.OpCvt64Fto32, ssa.OpCopy, TINT32},
	twoTypes{TFLOAT64, TINT64}: twoOpsAndType{ssa.OpCvt64Fto64, ssa.OpCopy, TINT64},
	// unsigned
	twoTypes{TUINT8, TFLOAT32}:  twoOpsAndType{ssa.OpZeroExt8to32, ssa.OpCvt32to32F, TINT32},
	twoTypes{TUINT16, TFLOAT32}: twoOpsAndType{ssa.OpZeroExt16to32, ssa.OpCvt32to32F, TINT32},
	twoTypes{TUINT32, TFLOAT32}: twoOpsAndType{ssa.OpZeroExt32to64, ssa.OpCvt64to32F, TINT64}, // go wide to dodge unsigned
	twoTypes{TUINT64, TFLOAT32}: twoOpsAndType{ssa.OpCopy, ssa.OpInvalid, TUINT64},            // Cvt64Uto32F, branchy code expansion instead

	twoTypes{TUINT8, TFLOAT64}:  twoOpsAndType{ssa.OpZeroExt8to32, ssa.OpCvt32to64F, TINT32},
	twoTypes{TUINT16, TFLOAT64}: twoOpsAndType{ssa.OpZeroExt16to32, ssa.OpCvt32to64F, TINT32},
	twoTypes{TUINT32, TFLOAT64}: twoOpsAndType{ssa.OpZeroExt32to64, ssa.OpCvt64to64F, TINT64}, // go wide to dodge unsigned
	twoTypes{TUINT64, TFLOAT64}: twoOpsAndType{ssa.OpCopy, ssa.OpInvalid, TUINT64},            // Cvt64Uto64F, branchy code expansion instead

	twoTypes{TFLOAT32, TUINT8}:  twoOpsAndType{ssa.OpCvt32Fto32, ssa.OpTrunc32to8, TINT32},
	twoTypes{TFLOAT32, TUINT16}: twoOpsAndType{ssa.OpCvt32Fto32, ssa.OpTrunc32to16, TINT32},
	twoTypes{TFLOAT32, TUINT32}: twoOpsAndType{ssa.OpCvt32Fto64, ssa.OpTrunc64to32, TINT64}, // go wide to dodge unsigned
	twoTypes{TFLOAT32, TUINT64}: twoOpsAndType{ssa.OpInvalid, ssa.OpCopy, TUINT64},          // Cvt32Fto64U, branchy code expansion instead

	twoTypes{TFLOAT64, TUINT8}:  twoOpsAndType{ssa.OpCvt64Fto32, ssa.OpTrunc32to8, TINT32},
	twoTypes{TFLOAT64, TUINT16}: twoOpsAndType{ssa.OpCvt64Fto32, ssa.OpTrunc32to16, TINT32},
	twoTypes{TFLOAT64, TUINT32}: twoOpsAndType{ssa.OpCvt64Fto64, ssa.OpTrunc64to32, TINT64}, // go wide to dodge unsigned
	twoTypes{TFLOAT64, TUINT64}: twoOpsAndType{ssa.OpInvalid, ssa.OpCopy, TUINT64},          // Cvt64Fto64U, branchy code expansion instead

	// float
	twoTypes{TFLOAT64, TFLOAT32}: twoOpsAndType{ssa.OpCvt64Fto32F, ssa.OpCopy, TFLOAT32},
	twoTypes{TFLOAT64, TFLOAT64}: twoOpsAndType{ssa.OpRound64F, ssa.OpCopy, TFLOAT64},
	twoTypes{TFLOAT32, TFLOAT32}: twoOpsAndType{ssa.OpRound32F, ssa.OpCopy, TFLOAT32},
	twoTypes{TFLOAT32, TFLOAT64}: twoOpsAndType{ssa.OpCvt32Fto64F, ssa.OpCopy, TFLOAT64},
}

// this map is used only for 32-bit arch, and only includes the difference
// on 32-bit arch, don't use int64<->float conversion for uint32
var fpConvOpToSSA32 = map[twoTypes]twoOpsAndType{
	twoTypes{TUINT32, TFLOAT32}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt32Uto32F, TUINT32},
	twoTypes{TUINT32, TFLOAT64}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt32Uto64F, TUINT32},
	twoTypes{TFLOAT32, TUINT32}: twoOpsAndType{ssa.OpCvt32Fto32U, ssa.OpCopy, TUINT32},
	twoTypes{TFLOAT64, TUINT32}: twoOpsAndType{ssa.OpCvt64Fto32U, ssa.OpCopy, TUINT32},
}

// uint64<->float conversions, only on machines that have instructions for that
var uint64fpConvOpToSSA = map[twoTypes]twoOpsAndType{
	twoTypes{TUINT64, TFLOAT32}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt64Uto32F, TUINT64},
	twoTypes{TUINT64, TFLOAT64}: twoOpsAndType{ssa.OpCopy, ssa.OpCvt64Uto64F, TUINT64},
	twoTypes{TFLOAT32, TUINT64}: twoOpsAndType{ssa.OpCvt32Fto64U, ssa.OpCopy, TUINT64},
	twoTypes{TFLOAT64, TUINT64}: twoOpsAndType{ssa.OpCvt64Fto64U, ssa.OpCopy, TUINT64},
}

var shiftOpToSSA = map[opAndTwoTypes]ssa.Op{
	opAndTwoTypes{OLSH, TINT8, TUINT8}:   ssa.OpLsh8x8,
	opAndTwoTypes{OLSH, TUINT8, TUINT8}:  ssa.OpLsh8x8,
	opAndTwoTypes{OLSH, TINT8, TUINT16}:  ssa.OpLsh8x16,
	opAndTwoTypes{OLSH, TUINT8, TUINT16}: ssa.OpLsh8x16,
	opAndTwoTypes{OLSH, TINT8, TUINT32}:  ssa.OpLsh8x32,
	opAndTwoTypes{OLSH, TUINT8, TUINT32}: ssa.OpLsh8x32,
	opAndTwoTypes{OLSH, TINT8, TUINT64}:  ssa.OpLsh8x64,
	opAndTwoTypes{OLSH, TUINT8, TUINT64}: ssa.OpLsh8x64,

	opAndTwoTypes{OLSH, TINT16, TUINT8}:   ssa.OpLsh16x8,
	opAndTwoTypes{OLSH, TUINT16, TUINT8}:  ssa.OpLsh16x8,
	opAndTwoTypes{OLSH, TINT16, TUINT16}:  ssa.OpLsh16x16,
	opAndTwoTypes{OLSH, TUINT16, TUINT16}: ssa.OpLsh16x16,
	opAndTwoTypes{OLSH, TINT16, TUINT32}:  ssa.OpLsh16x32,
	opAndTwoTypes{OLSH, TUINT16, TUINT32}: ssa.OpLsh16x32,
	opAndTwoTypes{OLSH, TINT16, TUINT64}:  ssa.OpLsh16x64,
	opAndTwoTypes{OLSH, TUINT16, TUINT64}: ssa.OpLsh16x64,

	opAndTwoTypes{OLSH, TINT32, TUINT8}:   ssa.OpLsh32x8,
	opAndTwoTypes{OLSH, TUINT32, TUINT8}:  ssa.OpLsh32x8,
	opAndTwoTypes{OLSH, TINT32, TUINT16}:  ssa.OpLsh32x16,
	opAndTwoTypes{OLSH, TUINT32, TUINT16}: ssa.OpLsh32x16,
	opAndTwoTypes{OLSH, TINT32, TUINT32}:  ssa.OpLsh32x32,
	opAndTwoTypes{OLSH, TUINT32, TUINT32}: ssa.OpLsh32x32,
	opAndTwoTypes{OLSH, TINT32, TUINT64}:  ssa.OpLsh32x64,
	opAndTwoTypes{OLSH, TUINT32, TUINT64}: ssa.OpLsh32x64,

	opAndTwoTypes{OLSH, TINT64, TUINT8}:   ssa.OpLsh64x8,
	opAndTwoTypes{OLSH, TUINT64, TUINT8}:  ssa.OpLsh64x8,
	opAndTwoTypes{OLSH, TINT64, TUINT16}:  ssa.OpLsh64x16,
	opAndTwoTypes{OLSH, TUINT64, TUINT16}: ssa.OpLsh64x16,
	opAndTwoTypes{OLSH, TINT64, TUINT32}:  ssa.OpLsh64x32,
	opAndTwoTypes{OLSH, TUINT64, TUINT32}: ssa.OpLsh64x32,
	opAndTwoTypes{OLSH, TINT64, TUINT64}:  ssa.OpLsh64x64,
	opAndTwoTypes{OLSH, TUINT64, TUINT64}: ssa.OpLsh64x64,

	opAndTwoTypes{ORSH, TINT8, TUINT8}:   ssa.OpRsh8x8,
	opAndTwoTypes{ORSH, TUINT8, TUINT8}:  ssa.OpRsh8Ux8,
	opAndTwoTypes{ORSH, TINT8, TUINT16}:  ssa.OpRsh8x16,
	opAndTwoTypes{ORSH, TUINT8, TUINT16}: ssa.OpRsh8Ux16,
	opAndTwoTypes{ORSH, TINT8, TUINT32}:  ssa.OpRsh8x32,
	opAndTwoTypes{ORSH, TUINT8, TUINT32}: ssa.OpRsh8Ux32,
	opAndTwoTypes{ORSH, TINT8, TUINT64}:  ssa.OpRsh8x64,
	opAndTwoTypes{ORSH, TUINT8, TUINT64}: ssa.OpRsh8Ux64,

	opAndTwoTypes{ORSH, TINT16, TUINT8}:   ssa.OpRsh16x8,
	opAndTwoTypes{ORSH, TUINT16, TUINT8}:  ssa.OpRsh16Ux8,
	opAndTwoTypes{ORSH, TINT16, TUINT16}:  ssa.OpRsh16x16,
	opAndTwoTypes{ORSH, TUINT16, TUINT16}: ssa.OpRsh16Ux16,
	opAndTwoTypes{ORSH, TINT16, TUINT32}:  ssa.OpRsh16x32,
	opAndTwoTypes{ORSH, TUINT16, TUINT32}: ssa.OpRsh16Ux32,
	opAndTwoTypes{ORSH, TINT16, TUINT64}:  ssa.OpRsh16x64,
	opAndTwoTypes{ORSH, TUINT16, TUINT64}: ssa.OpRsh16Ux64,

	opAndTwoTypes{ORSH, TINT32, TUINT8}:   ssa.OpRsh32x8,
	opAndTwoTypes{ORSH, TUINT32, TUINT8}:  ssa.OpRsh32Ux8,
	opAndTwoTypes{ORSH, TINT32, TUINT16}:  ssa.OpRsh32x16,
	opAndTwoTypes{ORSH, TUINT32, TUINT16}: ssa.OpRsh32Ux16,
	opAndTwoTypes{ORSH, TINT32, TUINT32}:  ssa.OpRsh32x32,
	opAndTwoTypes{ORSH, TUINT32, TUINT32}: ssa.OpRsh32Ux32,
	opAndTwoTypes{ORSH, TINT32, TUINT64}:  ssa.OpRsh32x64,
	opAndTwoTypes{ORSH, TUINT32, TUINT64}: ssa.OpRsh32Ux64,

	opAndTwoTypes{ORSH, TINT64, TUINT8}:   ssa.OpRsh64x8,
	opAndTwoTypes{ORSH, TUINT64, TUINT8}:  ssa.OpRsh64Ux8,
	opAndTwoTypes{ORSH, TINT64, TUINT16}:  ssa.OpRsh64x16,
	opAndTwoTypes{ORSH, TUINT64, TUINT16}: ssa.OpRsh64Ux16,
	opAndTwoTypes{ORSH, TINT64, TUINT32}:  ssa.OpRsh64x32,
	opAndTwoTypes{ORSH, TUINT64, TUINT32}: ssa.OpRsh64Ux32,
	opAndTwoTypes{ORSH, TINT64, TUINT64}:  ssa.OpRsh64x64,
	opAndTwoTypes{ORSH, TUINT64, TUINT64}: ssa.OpRsh64Ux64,
}

func (s *state) ssaShiftOp(op Op, t *types.Type, u *types.Type) ssa.Op {
	etype1 := s.concreteEtype(t)
	etype2 := s.concreteEtype(u)
	x, ok := shiftOpToSSA[opAndTwoTypes{op, etype1, etype2}]
	if !ok {
		s.Fatalf("unhandled shift op %v etype=%s/%s", op, etype1, etype2)
	}
	return x
}

// expr converts the expression n to ssa, adds it to s and returns the ssa result.
func (s *state) expr(n *Node) *ssa.Value {
	if !(n.Op == ONAME || n.Op == OLITERAL && n.Sym != nil) {
		// ONAMEs and named OLITERALs have the line number
		// of the decl, not the use. See issue 14742.
		s.pushLine(n.Pos)
		defer s.popLine()
	}

	s.stmtList(n.Ninit)
	switch n.Op {
	case OBYTES2STRTMP:
		slice := s.expr(n.Left)
		ptr := s.newValue1(ssa.OpSlicePtr, s.f.Config.Types.BytePtr, slice)
		len := s.newValue1(ssa.OpSliceLen, types.Types[TINT], slice)
		return s.newValue2(ssa.OpStringMake, n.Type, ptr, len)
	case OSTR2BYTESTMP:
		str := s.expr(n.Left)
		ptr := s.newValue1(ssa.OpStringPtr, s.f.Config.Types.BytePtr, str)
		len := s.newValue1(ssa.OpStringLen, types.Types[TINT], str)
		return s.newValue3(ssa.OpSliceMake, n.Type, ptr, len, len)
	case OCFUNC:
		aux := n.Left.Sym.Linksym()
		return s.entryNewValue1A(ssa.OpAddr, n.Type, aux, s.sb)
	case ONAME:
		if n.Class() == PFUNC {
			// "value" of a function is the address of the function's closure
			sym := funcsym(n.Sym).Linksym()
			return s.entryNewValue1A(ssa.OpAddr, types.NewPtr(n.Type), sym, s.sb)
		}
		if s.canSSA(n) {
			return s.variable(n, n.Type)
		}
		addr := s.addr(n)
		return s.load(n.Type, addr)
	case OCLOSUREVAR:
		addr := s.addr(n)
		return s.load(n.Type, addr)
	case OLITERAL:
		switch u := n.Val().U.(type) {
		case *Mpint:
			i := u.Int64()
			switch n.Type.Size() {
			case 1:
				return s.constInt8(n.Type, int8(i))
			case 2:
				return s.constInt16(n.Type, int16(i))
			case 4:
				return s.constInt32(n.Type, int32(i))
			case 8:
				return s.constInt64(n.Type, i)
			default:
				s.Fatalf("bad integer size %d", n.Type.Size())
				return nil
			}
		case string:
			if u == "" {
				return s.constEmptyString(n.Type)
			}
			return s.entryNewValue0A(ssa.OpConstString, n.Type, u)
		case bool:
			return s.constBool(u)
		case *NilVal:
			t := n.Type
			switch {
			case t.IsSlice():
				return s.constSlice(t)
			case t.IsInterface():
				return s.constInterface(t)
			default:
				return s.constNil(t)
			}
		case *Mpflt:
			switch n.Type.Size() {
			case 4:
				return s.constFloat32(n.Type, u.Float32())
			case 8:
				return s.constFloat64(n.Type, u.Float64())
			default:
				s.Fatalf("bad float size %d", n.Type.Size())
				return nil
			}
		case *Mpcplx:
			r := &u.Real
			i := &u.Imag
			switch n.Type.Size() {
			case 8:
				pt := types.Types[TFLOAT32]
				return s.newValue2(ssa.OpComplexMake, n.Type,
					s.constFloat32(pt, r.Float32()),
					s.constFloat32(pt, i.Float32()))
			case 16:
				pt := types.Types[TFLOAT64]
				return s.newValue2(ssa.OpComplexMake, n.Type,
					s.constFloat64(pt, r.Float64()),
					s.constFloat64(pt, i.Float64()))
			default:
				s.Fatalf("bad float size %d", n.Type.Size())
				return nil
			}

		default:
			s.Fatalf("unhandled OLITERAL %v", n.Val().Ctype())
			return nil
		}
	case OCONVNOP:
		to := n.Type
		from := n.Left.Type

		// Assume everything will work out, so set up our return value.
		// Anything interesting that happens from here is a fatal.
		x := s.expr(n.Left)

		// Special case for not confusing GC and liveness.
		// We don't want pointers accidentally classified
		// as not-pointers or vice-versa because of copy
		// elision.
		if to.IsPtrShaped() != from.IsPtrShaped() {
			return s.newValue2(ssa.OpConvert, to, x, s.mem())
		}

		v := s.newValue1(ssa.OpCopy, to, x) // ensure that v has the right type

		// CONVNOP closure
		if to.Etype == TFUNC && from.IsPtrShaped() {
			return v
		}

		// named <--> unnamed type or typed <--> untyped const
		if from.Etype == to.Etype {
			return v
		}

		// unsafe.Pointer <--> *T
		if to.IsUnsafePtr() && from.IsPtrShaped() || from.IsUnsafePtr() && to.IsPtrShaped() {
			return v
		}

		// map <--> *hmap
		if to.Etype == TMAP && from.IsPtr() &&
			to.MapType().Hmap == from.Elem() {
			return v
		}

		dowidth(from)
		dowidth(to)
		if from.Width != to.Width {
			s.Fatalf("CONVNOP width mismatch %v (%d) -> %v (%d)\n", from, from.Width, to, to.Width)
			return nil
		}
		if etypesign(from.Etype) != etypesign(to.Etype) {
			s.Fatalf("CONVNOP sign mismatch %v (%s) -> %v (%s)\n", from, from.Etype, to, to.Etype)
			return nil
		}

		if instrumenting {
			// These appear to be fine, but they fail the
			// integer constraint below, so okay them here.
			// Sample non-integer conversion: map[string]string -> *uint8
			return v
		}

		if etypesign(from.Etype) == 0 {
			s.Fatalf("CONVNOP unrecognized non-integer %v -> %v\n", from, to)
			return nil
		}

		// integer, same width, same sign
		return v

	case OCONV:
		x := s.expr(n.Left)
		ft := n.Left.Type // from type
		tt := n.Type      // to type
		if ft.IsBoolean() && tt.IsKind(TUINT8) {
			// Bool -> uint8 is generated internally when indexing into runtime.staticbyte.
			return s.newValue1(ssa.OpCopy, n.Type, x)
		}
		if ft.IsInteger() && tt.IsInteger() {
			var op ssa.Op
			if tt.Size() == ft.Size() {
				op = ssa.OpCopy
			} else if tt.Size() < ft.Size() {
				// truncation
				switch 10*ft.Size() + tt.Size() {
				case 21:
					op = ssa.OpTrunc16to8
				case 41:
					op = ssa.OpTrunc32to8
				case 42:
					op = ssa.OpTrunc32to16
				case 81:
					op = ssa.OpTrunc64to8
				case 82:
					op = ssa.OpTrunc64to16
				case 84:
					op = ssa.OpTrunc64to32
				default:
					s.Fatalf("weird integer truncation %v -> %v", ft, tt)
				}
			} else if ft.IsSigned() {
				// sign extension
				switch 10*ft.Size() + tt.Size() {
				case 12:
					op = ssa.OpSignExt8to16
				case 14:
					op = ssa.OpSignExt8to32
				case 18:
					op = ssa.OpSignExt8to64
				case 24:
					op = ssa.OpSignExt16to32
				case 28:
					op = ssa.OpSignExt16to64
				case 48:
					op = ssa.OpSignExt32to64
				default:
					s.Fatalf("bad integer sign extension %v -> %v", ft, tt)
				}
			} else {
				// zero extension
				switch 10*ft.Size() + tt.Size() {
				case 12:
					op = ssa.OpZeroExt8to16
				case 14:
					op = ssa.OpZeroExt8to32
				case 18:
					op = ssa.OpZeroExt8to64
				case 24:
					op = ssa.OpZeroExt16to32
				case 28:
					op = ssa.OpZeroExt16to64
				case 48:
					op = ssa.OpZeroExt32to64
				default:
					s.Fatalf("weird integer sign extension %v -> %v", ft, tt)
				}
			}
			return s.newValue1(op, n.Type, x)
		}

		if ft.IsFloat() || tt.IsFloat() {
			conv, ok := fpConvOpToSSA[twoTypes{s.concreteEtype(ft), s.concreteEtype(tt)}]
			if s.config.RegSize == 4 && thearch.LinkArch.Family != sys.MIPS && !s.softFloat {
				if conv1, ok1 := fpConvOpToSSA32[twoTypes{s.concreteEtype(ft), s.concreteEtype(tt)}]; ok1 {
					conv = conv1
				}
			}
			if thearch.LinkArch.Family == sys.ARM64 || thearch.LinkArch.Family == sys.Wasm || thearch.LinkArch.Family == sys.S390X || s.softFloat {
				if conv1, ok1 := uint64fpConvOpToSSA[twoTypes{s.concreteEtype(ft), s.concreteEtype(tt)}]; ok1 {
					conv = conv1
				}
			}

			if thearch.LinkArch.Family == sys.MIPS && !s.softFloat {
				if ft.Size() == 4 &&a