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codegen.go
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codegen.go
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// Copyright 2016 Google Inc. All Rights Reserved.
// This file is available under the Apache license.
package vm
import (
"fmt"
"regexp"
"time"
"github.com/golang/glog"
"github.com/google/mtail/metrics"
"github.com/google/mtail/metrics/datum"
"github.com/pkg/errors"
)
// codegen represents a code generator.
type codegen struct {
name string // Name of the program.
errors ErrorList // Any compile errors detected are accumulated here.
obj object // The object to return, if successful.
l []int // Label table for recording jump destinations.
decos []*decoNode // Decorator stack to unwind when entering decorated blocks.
}
// CodeGen is the function that compiles the program to bytecode and data.
func CodeGen(name string, ast astNode) (*object, error) {
c := &codegen{name: name}
Walk(c, ast)
c.writeJumps()
if len(c.errors) > 0 {
return nil, c.errors
}
return &c.obj, nil
}
func (c *codegen) errorf(pos *position, format string, args ...interface{}) {
e := "Internal compiler error, aborting compilation: " + fmt.Sprintf(format, args...)
c.errors.Add(pos, e)
}
func (c *codegen) emit(i instr) {
c.obj.prog = append(c.obj.prog, i)
}
// newLabel creates a new label to jump to
func (c *codegen) newLabel() (l int) {
l = len(c.l)
c.l = append(c.l, -1)
return
}
// setLabel points a label to the next instruction
func (c *codegen) setLabel(l int) {
c.l[l] = c.pc() + 1
}
// pc returns the program offset of the last instruction
func (c *codegen) pc() int {
return len(c.obj.prog) - 1
}
func (c *codegen) VisitBefore(node astNode) Visitor {
switch n := node.(type) {
case *declNode:
var name string
if n.exportedName != "" {
name = n.exportedName
} else {
name = n.name
}
// If the Type is not in the map, then default to metrics.Int. This is
// a hack for metrics that no type can be inferred, retaining
// historical behaviour.
t := n.Type()
if IsDimension(t) {
t = t.(*TypeOperator).Args[len(t.(*TypeOperator).Args)-1]
}
var dtyp datum.Type
switch {
case Equals(Float, t):
dtyp = metrics.Float
case Equals(String, t):
dtyp = metrics.String
default:
if !IsComplete(t) {
glog.Infof("Incomplete type %v for %#v", t, n)
}
dtyp = metrics.Int
}
m := metrics.NewMetric(name, c.name, n.kind, dtyp, n.keys...)
m.SetSource(n.Pos().String())
// Scalar counters can be initialized to zero. Dimensioned counters we
// don't know the values of the labels yet. Gauges and Timers we can't
// assume start at zero.
if len(n.keys) == 0 && n.kind == metrics.Counter {
d, err := m.GetDatum()
if err != nil {
c.errorf(n.Pos(), "%s", err)
return nil
}
// Initialize to zero at the zero time.
if dtyp == metrics.Int {
datum.SetInt(d, 0, time.Unix(0, 0))
} else {
datum.SetFloat(d, 0, time.Unix(0, 0))
}
}
m.Hidden = n.hidden
(*n.sym).Binding = m
n.sym.Addr = len(c.obj.m)
c.obj.m = append(c.obj.m, m)
return nil
case *condNode:
lElse := c.newLabel()
lEnd := c.newLabel()
if n.cond != nil {
Walk(c, n.cond)
c.emit(instr{jnm, lElse})
}
// Set matched flag false for children.
c.emit(instr{setmatched, false})
Walk(c, n.truthNode)
// Re-set matched flag to true for rest of current block.
c.emit(instr{setmatched, true})
if n.elseNode != nil {
c.emit(instr{jmp, lEnd})
}
c.setLabel(lElse)
if n.elseNode != nil {
Walk(c, n.elseNode)
}
c.setLabel(lEnd)
return nil
case *patternExprNode:
re, err := regexp.Compile(n.pattern)
if err != nil {
c.errorf(n.Pos(), "%s", err)
return nil
}
c.obj.re = append(c.obj.re, re)
// Store the location of this regular expression in the patterNode
n.index = len(c.obj.re) - 1
c.emit(instr{match, n.index})
case *stringConstNode:
c.obj.str = append(c.obj.str, n.text)
c.emit(instr{str, len(c.obj.str) - 1})
case *intConstNode:
c.emit(instr{push, n.i})
case *floatConstNode:
c.emit(instr{push, n.f})
case *idNode:
if n.sym.Kind != VarSymbol {
break
}
if n.sym == nil || n.sym.Binding == nil {
c.errorf(n.Pos(), "No metric bound to identifier %q", n.name)
return nil
}
c.emit(instr{mload, n.sym.Addr})
m := n.sym.Binding.(*metrics.Metric)
c.emit(instr{dload, len(m.Keys)})
if !n.lvalue {
t := n.Type()
if IsDimension(t) {
l := len(t.(*TypeOperator).Args)
t = t.(*TypeOperator).Args[l-1]
}
if Equals(t, Float) {
c.emit(instr{fget, nil})
} else if Equals(t, Int) {
c.emit(instr{iget, nil})
} else if Equals(t, String) {
c.emit(instr{sget, nil})
} else {
c.errorf(n.Pos(), "invalid type for get %q in %#v", n.Type(), n)
}
}
case *caprefNode:
if n.sym == nil || n.sym.Binding == nil {
c.errorf(n.Pos(), "No regular expression bound to capref %q", n.name)
return nil
}
rn := n.sym.Binding.(*patternExprNode)
// rn.index contains the index of the compiled regular expression object
// in the re slice of the object code
c.emit(instr{push, rn.index})
// n.sym.addr is the capture group offset
c.emit(instr{capref, n.sym.Addr})
case *decoDefNode:
// Do nothing, defs are inlined.
return nil
case *decoNode:
// Put the current block on the stack
c.decos = append(c.decos, n)
if n.def == nil {
c.errorf(n.Pos(), "No definition found for decorator %q", n.name)
return nil
}
// then iterate over the decorator's nodes
Walk(c, n.def.block)
c.decos = c.decos[:len(c.decos)-1]
return nil
case *nextNode:
// Visit the 'next' block on the decorated block stack
deco := c.decos[len(c.decos)-1]
Walk(c, deco.block)
return nil
case *otherwiseNode:
c.emit(instr{op: otherwise})
case *delNode:
Walk(c, n.n)
// overwrite the dload instruction
pc := c.pc()
c.obj.prog[pc].op = del
case *binaryExprNode:
switch n.op {
case AND:
lFalse := c.newLabel()
lEnd := c.newLabel()
Walk(c, n.lhs)
c.emit(instr{jnm, lFalse})
Walk(c, n.rhs)
c.emit(instr{jnm, lFalse})
c.emit(instr{push, true})
c.emit(instr{jmp, lEnd})
c.setLabel(lFalse)
c.emit(instr{push, false})
c.setLabel(lEnd)
return nil
case OR:
lTrue := c.newLabel()
lEnd := c.newLabel()
Walk(c, n.lhs)
c.emit(instr{jm, lTrue})
Walk(c, n.rhs)
c.emit(instr{jm, lTrue})
c.emit(instr{push, false})
c.emit(instr{jmp, lEnd})
c.setLabel(lTrue)
c.emit(instr{push, true})
c.setLabel(lEnd)
return nil
case ADD_ASSIGN:
if Equals(n.Type(), Float) {
// Double-emit the lhs so that it can be assigned to
Walk(c, n.lhs)
}
default:
// Didn't handle it, let normal walk proceed
return c
}
}
return c
}
var typedOperators = map[int]map[Type]opcode{
PLUS: {Int: iadd,
Float: fadd,
String: cat},
MINUS: {Int: isub,
Float: fsub},
MUL: {Int: imul,
Float: fmul},
DIV: {Int: idiv,
Float: fdiv},
MOD: {Int: imod,
Float: fmod},
POW: {Int: ipow,
Float: fpow},
ASSIGN: {Int: iset,
Float: fset,
String: sset},
}
func (c *codegen) VisitAfter(node astNode) {
switch n := node.(type) {
case *builtinNode:
arglen := 0
if n.args != nil {
arglen = len(n.args.(*exprlistNode).children)
}
switch n.name {
case "bool":
// TODO(jaq): Nothing, no support in VM yet.
case "int", "float", "string":
// len args should be 1
if arglen > 1 {
c.errorf(n.Pos(), "too many arguments to builtin %q: %#v", n.name, n)
return
}
if err := c.emitConversion(n.args.(*exprlistNode).children[0].Type(), n.Type()); err != nil {
c.errorf(n.Pos(), "%s on node %v", err.Error(), n)
return
}
default:
c.emit(instr{builtin[n.name], arglen})
}
case *unaryExprNode:
switch n.op {
case INC:
c.emit(instr{op: inc})
case NOT:
c.emit(instr{op: neg})
}
case *binaryExprNode:
switch n.op {
case LT, GT, LE, GE, EQ, NE:
lFail := c.newLabel()
lEnd := c.newLabel()
var cmpArg int
var jumpOp opcode
switch n.op {
case LT:
cmpArg = -1
jumpOp = jnm
case GT:
cmpArg = 1
jumpOp = jnm
case LE:
cmpArg = 1
jumpOp = jm
case GE:
cmpArg = -1
jumpOp = jm
case EQ:
cmpArg = 0
jumpOp = jnm
case NE:
cmpArg = 0
jumpOp = jm
}
cmpOp := cmp
if Equals(n.lhs.Type(), n.rhs.Type()) {
switch n.lhs.Type() {
case Float:
cmpOp = fcmp
case Int:
cmpOp = icmp
case String:
cmpOp = scmp
default:
cmpOp = cmp
}
}
c.emit(instr{cmpOp, cmpArg})
c.emit(instr{jumpOp, lFail})
c.emit(instr{push, true})
c.emit(instr{jmp, lEnd})
c.setLabel(lFail)
c.emit(instr{push, false})
c.setLabel(lEnd)
case ADD_ASSIGN:
// When operand is not nil, inc pops the delta from the stack.
// TODO(jaq): string concatenation, once datums can hold strings.
switch {
case Equals(n.Type(), Int):
c.emit(instr{inc, 0})
case Equals(n.Type(), Float):
// Already walked the lhs and rhs of this expression
c.emit(instr{fadd, nil})
// And a second lhs
c.emit(instr{fset, nil})
default:
c.errorf(n.Pos(), "invalid type for add-assignment: %v", n.op)
return
}
case PLUS, MINUS, MUL, DIV, MOD, POW, ASSIGN:
opmap, ok := typedOperators[n.op]
if !ok {
c.errorf(n.Pos(), "no typed operator for binary expression %v", n.op)
return
}
emitflag := false
for t, opcode := range opmap {
if Equals(n.Type(), t) {
c.emit(instr{op: opcode})
emitflag = true
break
}
}
if !emitflag {
c.errorf(n.Pos(), "invalid type for binary expression: %v", n.Type())
return
}
case BITAND:
c.emit(instr{op: and})
case BITOR:
c.emit(instr{op: or})
case XOR:
c.emit(instr{op: xor})
case SHL:
c.emit(instr{op: shl})
case SHR:
c.emit(instr{op: shr})
case MATCH:
// Cross fingers that last branch was a patternExprNode
c.obj.prog[c.pc()].op = smatch
case NOT_MATCH:
// Cross fingers that last branch was a patternExprNode
c.obj.prog[c.pc()].op = smatch
c.emit(instr{op: not})
case CONCAT:
// skip
default:
c.errorf(n.Pos(), "unexpected op %v", n.op)
}
case *convNode:
if err := c.emitConversion(n.n.Type(), n.Type()); err != nil {
c.errorf(n.Pos(), "internal error: %s on node %v", err.Error(), n)
return
}
}
}
func (c *codegen) emitConversion(inType, outType Type) error {
glog.V(2).Infof("Conversion: %q to %q", inType, outType)
if Equals(Int, inType) && Equals(Float, outType) {
c.emit(instr{op: i2f})
} else if Equals(String, inType) && Equals(Float, outType) {
c.emit(instr{op: s2f})
} else if Equals(String, inType) && Equals(Int, outType) {
c.emit(instr{op: s2i})
} else if Equals(Float, inType) && Equals(String, outType) {
c.emit(instr{op: f2s})
} else if Equals(Int, inType) && Equals(String, outType) {
c.emit(instr{op: i2s})
} else if Equals(Pattern, inType) && Equals(Bool, outType) {
// nothing, pattern is implicit bool
} else {
return errors.Errorf("can't convert %q to %q", inType, outType)
}
return nil
}
func (c *codegen) writeJumps() {
for j, i := range c.obj.prog {
switch i.op {
case jmp, jm, jnm:
index := i.opnd.(int)
if index > len(c.l) {
c.errorf(nil, "no jump at label %v, table is %v", i.opnd, c.l)
continue
}
offset := c.l[index]
if offset < 0 {
c.errorf(nil, "offset for label %v is negative, table is %v", i.opnd, c.l)
continue
}
c.obj.prog[j].opnd = c.l[index]
}
}
}