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cmd/compile: add saturating conversions on wasm

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This change adds the GOWASM option "satconv" to enable the generation
of experimental saturating (non-trapping) float-to-int conversions.
It improves the performance of the conversion by 42%.

Previously the conversions had already been augmented with helper
functions to have saturating behavior. Now Wasm.rules is always using
the new operation names and wasm/ssa.go is falling back to the helpers
if the feature is not enabled.

The feature is in phase 4 of the WebAssembly proposal process:
https://github.com/WebAssembly/meetings/blob/master/process/phases.md

More information on the feature can be found at:
https://github.com/WebAssembly/nontrapping-float-to-int-conversions/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md

Change-Id: Ic6c3688017054ede804b02b6b0ffd4a02ef33ad7
Reviewed-on: https://go-review.googlesource.com/c/go/+/170119
Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Richard Musiol 2019-03-24 12:14:27 +01:00 committed by Richard Musiol
parent 1abf3aa55b
commit cf8cc7f63c
12 changed files with 80 additions and 42 deletions
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1
doc/install-source.html
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@ -645,6 +645,7 @@ for which the compiler will target. The default is <code>power8</code>.
The default is to use no experimental features.
</p>
<ul>
<li><code>GOWASM=satconv</code>: generate <a href="https://github.com/WebAssembly/nontrapping-float-to-int-conversions/blob/master/proposals/nontrapping-float-to-int-conversion/Overview.md">saturating (non-trapping) float-to-int conversions</a></li>
<li><code>GOWASM=signext</code>: generate <a href="https://github.com/WebAssembly/sign-extension-ops/blob/master/proposals/sign-extension-ops/Overview.md">sign-extension operators</a></li>
</ul>
</li>

16
src/cmd/compile/internal/ssa/gen/Wasm.rules
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@ -84,14 +84,14 @@
(Cvt64Uto32F x) -> (LoweredRound32F (F64ConvertI64U x))
(Cvt64Uto64F x) -> (F64ConvertI64U x)
(Cvt32Fto32 x) -> (I64TruncF64S x)
(Cvt32Fto64 x) -> (I64TruncF64S x)
(Cvt64Fto32 x) -> (I64TruncF64S x)
(Cvt64Fto64 x) -> (I64TruncF64S x)
(Cvt32Fto32U x) -> (I64TruncF64U x)
(Cvt32Fto64U x) -> (I64TruncF64U x)
(Cvt64Fto32U x) -> (I64TruncF64U x)
(Cvt64Fto64U x) -> (I64TruncF64U x)
(Cvt32Fto32 x) -> (I64TruncSatF64S x)
(Cvt32Fto64 x) -> (I64TruncSatF64S x)
(Cvt64Fto32 x) -> (I64TruncSatF64S x)
(Cvt64Fto64 x) -> (I64TruncSatF64S x)
(Cvt32Fto32U x) -> (I64TruncSatF64U x)
(Cvt32Fto64U x) -> (I64TruncSatF64U x)
(Cvt64Fto32U x) -> (I64TruncSatF64U x)
(Cvt64Fto64U x) -> (I64TruncSatF64U x)
(Cvt32Fto64F x) -> x
(Cvt64Fto32F x) -> (LoweredRound32F x)

4
src/cmd/compile/internal/ssa/gen/WasmOps.go
View File

@ -187,8 +187,8 @@ func init() {
{name: "F64Mul", asm: "F64Mul", argLength: 2, reg: fp21, typ: "Float64"}, // arg0 * arg1
{name: "F64Div", asm: "F64Div", argLength: 2, reg: fp21, typ: "Float64"}, // arg0 / arg1
{name: "I64TruncF64S", asm: "I64TruncF64S", argLength: 1, reg: regInfo{inputs: []regMask{fp}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to a signed integer
{name: "I64TruncF64U", asm: "I64TruncF64U", argLength: 1, reg: regInfo{inputs: []regMask{fp}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to an unsigned integer
{name: "I64TruncSatF64S", asm: "I64TruncSatF64S", argLength: 1, reg: regInfo{inputs: []regMask{fp}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to a signed integer (saturating)
{name: "I64TruncSatF64U", asm: "I64TruncSatF64U", argLength: 1, reg: regInfo{inputs: []regMask{fp}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to an unsigned integer (saturating)
{name: "F64ConvertI64S", asm: "F64ConvertI64S", argLength: 1, reg: regInfo{inputs: []regMask{gp}, outputs: []regMask{fp}}, typ: "Float64"}, // converts the signed integer arg0 to a float
{name: "F64ConvertI64U", asm: "F64ConvertI64U", argLength: 1, reg: regInfo{inputs: []regMask{gp}, outputs: []regMask{fp}}, typ: "Float64"}, // converts the unsigned integer arg0 to a float

12
src/cmd/compile/internal/ssa/opGen.go
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@ -2132,8 +2132,8 @@ const (
OpWasmF64Sub
OpWasmF64Mul
OpWasmF64Div
OpWasmI64TruncF64S
OpWasmI64TruncF64U
OpWasmI64TruncSatF64S
OpWasmI64TruncSatF64U
OpWasmF64ConvertI64S
OpWasmF64ConvertI64U
OpWasmI64Extend8S
@ -28676,9 +28676,9 @@ var opcodeTable = [...]opInfo{
},
},
{
name: "I64TruncF64S",
name: "I64TruncSatF64S",
argLen: 1,
asm: wasm.AI64TruncF64S,
asm: wasm.AI64TruncSatF64S,
reg: regInfo{
inputs: []inputInfo{
{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15
@ -28689,9 +28689,9 @@ var opcodeTable = [...]opInfo{
},
},
{
name: "I64TruncF64U",
name: "I64TruncSatF64U",
argLen: 1,
asm: wasm.AI64TruncF64U,
asm: wasm.AI64TruncSatF64U,
reg: regInfo{
inputs: []inputInfo{
{0, 4294901760}, // F0 F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15

32
src/cmd/compile/internal/ssa/rewriteWasm.go
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@ -1095,10 +1095,10 @@ func rewriteValueWasm_OpCtz8NonZero_0(v *Value) bool {
func rewriteValueWasm_OpCvt32Fto32_0(v *Value) bool {
// match: (Cvt32Fto32 x)
// cond:
// result: (I64TruncF64S x)
// result: (I64TruncSatF64S x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64S)
v.reset(OpWasmI64TruncSatF64S)
v.AddArg(x)
return true
}
@ -1106,10 +1106,10 @@ func rewriteValueWasm_OpCvt32Fto32_0(v *Value) bool {
func rewriteValueWasm_OpCvt32Fto32U_0(v *Value) bool {
// match: (Cvt32Fto32U x)
// cond:
// result: (I64TruncF64U x)
// result: (I64TruncSatF64U x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64U)
v.reset(OpWasmI64TruncSatF64U)
v.AddArg(x)
return true
}
@ -1117,10 +1117,10 @@ func rewriteValueWasm_OpCvt32Fto32U_0(v *Value) bool {
func rewriteValueWasm_OpCvt32Fto64_0(v *Value) bool {
// match: (Cvt32Fto64 x)
// cond:
// result: (I64TruncF64S x)
// result: (I64TruncSatF64S x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64S)
v.reset(OpWasmI64TruncSatF64S)
v.AddArg(x)
return true
}
@ -1140,10 +1140,10 @@ func rewriteValueWasm_OpCvt32Fto64F_0(v *Value) bool {
func rewriteValueWasm_OpCvt32Fto64U_0(v *Value) bool {
// match: (Cvt32Fto64U x)
// cond:
// result: (I64TruncF64U x)
// result: (I64TruncSatF64U x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64U)
v.reset(OpWasmI64TruncSatF64U)
v.AddArg(x)
return true
}
@ -1215,10 +1215,10 @@ func rewriteValueWasm_OpCvt32to64F_0(v *Value) bool {
func rewriteValueWasm_OpCvt64Fto32_0(v *Value) bool {
// match: (Cvt64Fto32 x)
// cond:
// result: (I64TruncF64S x)
// result: (I64TruncSatF64S x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64S)
v.reset(OpWasmI64TruncSatF64S)
v.AddArg(x)
return true
}
@ -1237,10 +1237,10 @@ func rewriteValueWasm_OpCvt64Fto32F_0(v *Value) bool {
func rewriteValueWasm_OpCvt64Fto32U_0(v *Value) bool {
// match: (Cvt64Fto32U x)
// cond:
// result: (I64TruncF64U x)
// result: (I64TruncSatF64U x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64U)
v.reset(OpWasmI64TruncSatF64U)
v.AddArg(x)
return true
}
@ -1248,10 +1248,10 @@ func rewriteValueWasm_OpCvt64Fto32U_0(v *Value) bool {
func rewriteValueWasm_OpCvt64Fto64_0(v *Value) bool {
// match: (Cvt64Fto64 x)
// cond:
// result: (I64TruncF64S x)
// result: (I64TruncSatF64S x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64S)
v.reset(OpWasmI64TruncSatF64S)
v.AddArg(x)
return true
}
@ -1259,10 +1259,10 @@ func rewriteValueWasm_OpCvt64Fto64_0(v *Value) bool {
func rewriteValueWasm_OpCvt64Fto64U_0(v *Value) bool {
// match: (Cvt64Fto64U x)
// cond:
// result: (I64TruncF64U x)
// result: (I64TruncSatF64U x)
for {
x := v.Args[0]
v.reset(OpWasmI64TruncF64U)
v.reset(OpWasmI64TruncSatF64U)
v.AddArg(x)
return true
}

21
src/cmd/compile/internal/wasm/ssa.go
View File

@ -10,6 +10,7 @@ import (
"cmd/compile/internal/types"
"cmd/internal/obj"
"cmd/internal/obj/wasm"
"cmd/internal/objabi"
)
func Init(arch *gc.Arch) {
@ -307,15 +308,23 @@ func ssaGenValueOnStack(s *gc.SSAGenState, v *ssa.Value) {
}
s.Prog(wasm.AI64DivS)
case ssa.OpWasmI64TruncF64S:
case ssa.OpWasmI64TruncSatF64S:
getValue64(s, v.Args[0])
p := s.Prog(wasm.ACall)
p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: gc.WasmTruncS}
if objabi.GOWASM.SatConv {
s.Prog(v.Op.Asm())
} else {
p := s.Prog(wasm.ACall)
p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: gc.WasmTruncS}
}
case ssa.OpWasmI64TruncF64U:
case ssa.OpWasmI64TruncSatF64U:
getValue64(s, v.Args[0])
p := s.Prog(wasm.ACall)
p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: gc.WasmTruncU}
if objabi.GOWASM.SatConv {
s.Prog(v.Op.Asm())
} else {
p := s.Prog(wasm.ACall)
p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: gc.WasmTruncU}
}
case
ssa.OpWasmF64Neg, ssa.OpWasmF64ConvertI64S, ssa.OpWasmF64ConvertI64U,

2
src/cmd/go/alldocs.go
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@ -1581,7 +1581,7 @@
// Valid values are hardfloat (default), softfloat.
// GOWASM
// For GOARCH=wasm, comma-separated list of experimental WebAssembly features to use.
// Valid values are: signext.
// Valid values are satconv, signext.
//
// Special-purpose environment variables:
//

2
src/cmd/go/internal/help/helpdoc.go
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@ -565,7 +565,7 @@ Architecture-specific environment variables:
Valid values are hardfloat (default), softfloat.
GOWASM
For GOARCH=wasm, comma-separated list of experimental WebAssembly features to use.
Valid values are: signext.
Valid values are satconv, signext.
Special-purpose environment variables:

9
src/cmd/internal/obj/wasm/a.out.go
View File

@ -216,6 +216,15 @@ const (
AI64Extend16S
AI64Extend32S
AI32TruncSatF32S // opcode 0xFC 0x00
AI32TruncSatF32U
AI32TruncSatF64S
AI32TruncSatF64U
AI64TruncSatF32S
AI64TruncSatF32U
AI64TruncSatF64S
AI64TruncSatF64U
ALast // Sentinel: End of low-level WebAssembly instructions.
ARESUMEPOINT

8
src/cmd/internal/obj/wasm/anames.go
View File

@ -182,6 +182,14 @@ var Anames = []string{
"I64Extend8S",
"I64Extend16S",
"I64Extend32S",
"I32TruncSatF32S",
"I32TruncSatF32U",
"I32TruncSatF64S",
"I32TruncSatF64U",
"I64TruncSatF32S",
"I64TruncSatF32U",
"I64TruncSatF64S",
"I64TruncSatF64U",
"Last",
"RESUMEPOINT",
"CALLNORESUME",

9
src/cmd/internal/obj/wasm/wasmobj.go
View File

@ -886,7 +886,7 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
}
switch {
case p.As < AUnreachable || p.As >= ALast:
case p.As < AUnreachable:
panic(fmt.Sprintf("unexpected assembler op: %s", p.As))
case p.As < AEnd:
w.WriteByte(byte(p.As - AUnreachable + 0x00))
@ -894,8 +894,13 @@ func assemble(ctxt *obj.Link, s *obj.LSym, newprog obj.ProgAlloc) {
w.WriteByte(byte(p.As - AEnd + 0x0B))
case p.As < AI32Load:
w.WriteByte(byte(p.As - ADrop + 0x1A))
default:
case p.As < AI32TruncSatF32S:
w.WriteByte(byte(p.As - AI32Load + 0x28))
case p.As < ALast:
w.WriteByte(0xFC)
w.WriteByte(byte(p.As - AI32TruncSatF32S + 0x00))
default:
panic(fmt.Sprintf("unexpected assembler op: %s", p.As))
}
switch p.As {

6
src/cmd/internal/objabi/util.go
View File

@ -79,10 +79,14 @@ func goppc64() int {
type gowasmFeatures struct {
SignExt bool
SatConv bool
}
func (f *gowasmFeatures) String() string {
var flags []string
if f.SatConv {
flags = append(flags, "satconv")
}
if f.SignExt {
flags = append(flags, "signext")
}
@ -92,6 +96,8 @@ func (f *gowasmFeatures) String() string {
func gowasm() (f gowasmFeatures) {
for _, opt := range strings.Split(envOr("GOWASM", ""), ",") {
switch opt {
case "satconv":
f.SatConv = true
case "signext":
f.SignExt = true
case "":