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cmd/compile: in wasm, allocate approximately right number of locals for functions #28116

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cmd/compile: in wasm, allocate approximately right number of locals for functions #28116

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73 changes: 63 additions & 10 deletions src/cmd/internal/obj/wasm/wasmobj.go
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Original file line number Diff line number Diff line change
Expand Up @@ -705,11 +705,42 @@ func regAddr(reg int16) obj.Addr {
return obj.Addr{Type: obj.TYPE_REG, Reg: reg}
}

// countRegisters returns the number of integer and float registers used by s.
// It does so by looking for the maximum I* and R* registers.
func countRegisters(s *obj.LSym) (numI, numF int16) {
for p := s.Func.Text; p != nil; p = p.Link {
var reg int16
switch p.As {
case AGet:
reg = p.From.Reg
case ASet:
reg = p.To.Reg
case ATee:
reg = p.To.Reg
default:
continue
}
if reg >= REG_R0 && reg <= REG_R15 {
if n := reg - REG_R0 + 1; numI < n {
numI = n
}
} else if reg >= REG_F0 && reg <= REG_F15 {
if n := reg - REG_F0 + 1; numF < n {
numF = n
}
}
}
return
}

func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
w := new(bytes.Buffer)

numI, numF := countRegisters(s)

// Function starts with declaration of locals: numbers and types.
switch s.Name {
// memchr and memcmp don't use the normal Go calling convention and need i32 variables.
case "memchr":
writeUleb128(w, 1) // number of sets of locals
writeUleb128(w, 3) // number of locals
Expand All @@ -719,11 +750,23 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
writeUleb128(w, 2) // number of locals
w.WriteByte(0x7F) // i32
default:
writeUleb128(w, 2) // number of sets of locals
writeUleb128(w, 16) // number of locals
w.WriteByte(0x7E) // i64
writeUleb128(w, 16) // number of locals
w.WriteByte(0x7C) // f64
numTypes := 0
if numI > 0 {
numTypes++
}
if numF > 0 {
numTypes++
}

writeUleb128(w, uint64(numTypes))
if numI > 0 {
writeUleb128(w, uint64(numI)) // number of locals
w.WriteByte(0x7E) // i64
}
if numF > 0 {
writeUleb128(w, uint64(numF)) // number of locals
w.WriteByte(0x7C) // f64
}
}

for p := s.Func.Text; p != nil; p = p.Link {
Expand All @@ -737,9 +780,12 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
case reg >= REG_PC_F && reg <= REG_RUN:
w.WriteByte(0x23) // get_global
writeUleb128(w, uint64(reg-REG_PC_F))
case reg >= REG_R0 && reg <= REG_F15:
w.WriteByte(0x20) // get_local
case reg >= REG_R0 && reg <= REG_R15:
w.WriteByte(0x20) // get_local (i64)
writeUleb128(w, uint64(reg-REG_R0))
case reg >= REG_F0 && reg <= REG_F15:
w.WriteByte(0x20) // get_local (f64)
writeUleb128(w, uint64(numI+(reg-REG_F0)))
default:
panic("bad Get: invalid register")
}
Expand All @@ -761,7 +807,11 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
} else {
w.WriteByte(0x21) // set_local
}
writeUleb128(w, uint64(reg-REG_R0))
if reg <= REG_R15 {
writeUleb128(w, uint64(reg-REG_R0))
} else {
writeUleb128(w, uint64(numI+(reg-REG_F0)))
}
default:
panic("bad Set: invalid register")
}
Expand All @@ -773,9 +823,12 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
}
reg := p.To.Reg
switch {
case reg >= REG_R0 && reg <= REG_F15:
w.WriteByte(0x22) // tee_local
case reg >= REG_R0 && reg <= REG_R15:
w.WriteByte(0x22) // tee_local (i64)
writeUleb128(w, uint64(reg-REG_R0))
case reg >= REG_F0 && reg <= REG_F15:
w.WriteByte(0x22) // tee_local (f64)
writeUleb128(w, uint64(numI+(reg-REG_F0)))
default:
panic("bad Tee: invalid register")
}
Expand Down