cmd/compile, runtime: always enable Wasm signext and satconv features

These features have been standardized since at least Wasm 2.0.
Always enable them.

The corresponding GOWASM settings are now no-op.

Change-Id: I0e59f21696a69a4e289127988aad629a720b002b
Reviewed-on: https://go-review.googlesource.com/c/go/+/707855
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>

src/cmd/compile/internal/ssa/_gen/Wasm.rules

@@ -55,12 +55,9 @@
 (ZeroExt32to64        x:(I64Load32U _ _)) => x
 (ZeroExt16to(64|32)   x:(I64Load16U _ _)) => x
 (ZeroExt8to(64|32|16) x:(I64Load8U  _ _)) => x
-(SignExt32to64        x) && buildcfg.GOWASM.SignExt => (I64Extend32S x)
-(SignExt8to(64|32|16) x) && buildcfg.GOWASM.SignExt => (I64Extend8S x)
-(SignExt16to(64|32)   x) && buildcfg.GOWASM.SignExt => (I64Extend16S x)
-(SignExt32to64        x) => (I64ShrS (I64Shl x (I64Const [32])) (I64Const [32]))
-(SignExt16to(64|32)   x) => (I64ShrS (I64Shl x (I64Const [48])) (I64Const [48]))
-(SignExt8to(64|32|16) x) => (I64ShrS (I64Shl x (I64Const [56])) (I64Const [56]))
+(SignExt32to64        x) => (I64Extend32S x)
+(SignExt8to(64|32|16) x) => (I64Extend8S x)
+(SignExt16to(64|32)   x) => (I64Extend16S x)
 (ZeroExt32to64        x) => (I64And x (I64Const [0xffffffff]))
 (ZeroExt16to(64|32)   x) => (I64And x (I64Const [0xffff]))
 (ZeroExt8to(64|32|16) x) => (I64And x (I64Const [0xff]))

src/cmd/compile/internal/ssa/rewriteWasm.go

@@ -2,7 +2,6 @@
 
 package ssa
 
-import "internal/buildcfg"
 import "math"
 import "cmd/compile/internal/types"
 
@@ -3202,8 +3201,6 @@ func rewriteValueWasm_OpRsh8x8(v *Value) bool {
 }
 func rewriteValueWasm_OpSignExt16to32(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt16to32 x:(I64Load16S _ _))
 	// result: x
 	for {
@@ -3215,34 +3212,16 @@ func rewriteValueWasm_OpSignExt16to32(v *Value) bool {
 		return true
 	}
 	// match: (SignExt16to32 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend16S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend16S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt16to32 x)
-	// result: (I64ShrS (I64Shl x (I64Const [48])) (I64Const [48]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(48)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSignExt16to64(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt16to64 x:(I64Load16S _ _))
 	// result: x
 	for {
@@ -3254,34 +3233,16 @@ func rewriteValueWasm_OpSignExt16to64(v *Value) bool {
 		return true
 	}
 	// match: (SignExt16to64 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend16S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend16S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt16to64 x)
-	// result: (I64ShrS (I64Shl x (I64Const [48])) (I64Const [48]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(48)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSignExt32to64(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt32to64 x:(I64Load32S _ _))
 	// result: x
 	for {
@@ -3293,34 +3254,16 @@ func rewriteValueWasm_OpSignExt32to64(v *Value) bool {
 		return true
 	}
 	// match: (SignExt32to64 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend32S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend32S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt32to64 x)
-	// result: (I64ShrS (I64Shl x (I64Const [32])) (I64Const [32]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(32)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSignExt8to16(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt8to16 x:(I64Load8S _ _))
 	// result: x
 	for {
@@ -3332,34 +3275,16 @@ func rewriteValueWasm_OpSignExt8to16(v *Value) bool {
 		return true
 	}
 	// match: (SignExt8to16 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend8S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend8S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt8to16 x)
-	// result: (I64ShrS (I64Shl x (I64Const [56])) (I64Const [56]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(56)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSignExt8to32(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt8to32 x:(I64Load8S _ _))
 	// result: x
 	for {
@@ -3371,34 +3296,16 @@ func rewriteValueWasm_OpSignExt8to32(v *Value) bool {
 		return true
 	}
 	// match: (SignExt8to32 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend8S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend8S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt8to32 x)
-	// result: (I64ShrS (I64Shl x (I64Const [56])) (I64Const [56]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(56)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSignExt8to64(v *Value) bool {
 	v_0 := v.Args[0]
-	b := v.Block
-	typ := &b.Func.Config.Types
 	// match: (SignExt8to64 x:(I64Load8S _ _))
 	// result: x
 	for {
@@ -3410,29 +3317,13 @@ func rewriteValueWasm_OpSignExt8to64(v *Value) bool {
 		return true
 	}
 	// match: (SignExt8to64 x)
-	// cond: buildcfg.GOWASM.SignExt
 	// result: (I64Extend8S x)
 	for {
 		x := v_0
-		if !(buildcfg.GOWASM.SignExt) {
-			break
-		}
 		v.reset(OpWasmI64Extend8S)
 		v.AddArg(x)
 		return true
 	}
-	// match: (SignExt8to64 x)
-	// result: (I64ShrS (I64Shl x (I64Const [56])) (I64Const [56]))
-	for {
-		x := v_0
-		v.reset(OpWasmI64ShrS)
-		v0 := b.NewValue0(v.Pos, OpWasmI64Shl, typ.Int64)
-		v1 := b.NewValue0(v.Pos, OpWasmI64Const, typ.Int64)
-		v1.AuxInt = int64ToAuxInt(56)
-		v0.AddArg2(x, v1)
-		v.AddArg2(v0, v1)
-		return true
-	}
 }
 func rewriteValueWasm_OpSlicemask(v *Value) bool {
 	v_0 := v.Args[0]

src/cmd/compile/internal/wasm/ssa.go

@@ -14,7 +14,6 @@ import (
 	"cmd/compile/internal/types"
 	"cmd/internal/obj"
 	"cmd/internal/obj/wasm"
-	"internal/buildcfg"
 )
 
 /*
@@ -425,27 +424,11 @@ func ssaGenValueOnStack(s *ssagen.State, v *ssa.Value, extend bool) {
 
 	case ssa.OpWasmI64TruncSatF32S, ssa.OpWasmI64TruncSatF64S:
 		getValue64(s, v.Args[0])
-		if buildcfg.GOWASM.SatConv {
 		s.Prog(v.Op.Asm())
-		} else {
-			if v.Op == ssa.OpWasmI64TruncSatF32S {
-				s.Prog(wasm.AF64PromoteF32)
-			}
-			p := s.Prog(wasm.ACall)
-			p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: ir.Syms.WasmTruncS}
-		}
 
 	case ssa.OpWasmI64TruncSatF32U, ssa.OpWasmI64TruncSatF64U:
 		getValue64(s, v.Args[0])
-		if buildcfg.GOWASM.SatConv {
 		s.Prog(v.Op.Asm())
-		} else {
-			if v.Op == ssa.OpWasmI64TruncSatF32U {
-				s.Prog(wasm.AF64PromoteF32)
-			}
-			p := s.Prog(wasm.ACall)
-			p.To = obj.Addr{Type: obj.TYPE_MEM, Name: obj.NAME_EXTERN, Sym: ir.Syms.WasmTruncU}
-		}
 
 	case ssa.OpWasmF32DemoteF64:
 		getValue64(s, v.Args[0])

src/internal/buildcfg/cfg.go

@@ -321,18 +321,13 @@ func goriscv64() int {
 }
 
 type gowasmFeatures struct {
-	SatConv bool
-	SignExt bool
+	// Legacy features, now always enabled
+	//SatConv bool
+	//SignExt bool
 }
 
 func (f gowasmFeatures) String() string {
 	var flags []string
-	if f.SatConv {
-		flags = append(flags, "satconv")
-	}
-	if f.SignExt {
-		flags = append(flags, "signext")
-	}
 	return strings.Join(flags, ",")
 }
 
@@ -340,9 +335,9 @@ func gowasm() (f gowasmFeatures) {
 	for opt := range strings.SplitSeq(envOr("GOWASM", ""), ",") {
 		switch opt {
 		case "satconv":
-			f.SatConv = true
+			// ignore, always enabled
 		case "signext":
-			f.SignExt = true
+			// ignore, always enabled
 		case "":
 			// ignore
 		default:
@@ -452,12 +447,10 @@ func gogoarchTags() []string {
 		return list
 	case "wasm":
 		var list []string
-		if GOWASM.SatConv {
+		// SatConv is always enabled
 		list = append(list, GOARCH+".satconv")
-		}
-		if GOWASM.SignExt {
+		// SignExt is always enabled
 		list = append(list, GOARCH+".signext")
-		}
 		return list
 	}
 	return nil

src/runtime/conv_wasm_test.go

@@ -11,6 +11,8 @@ import (
 var res int64
 var ures uint64
 
+// TODO: This test probably should be in a different place.
+
 func TestFloatTruncation(t *testing.T) {
 	testdata := []struct {
 		input      float64
@@ -21,36 +23,37 @@ func TestFloatTruncation(t *testing.T) {
 		// max +- 1
 		{
 			input:      0x7fffffffffffffff,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0x8000000000000000,
 		},
 		// For out-of-bounds conversion, the result is implementation-dependent.
-		// This test verifies the implementation of wasm architecture.
+		// This test verifies the implementation of wasm architecture, which is,
+		// saturating to the min/max value.
 		{
 			input:      0x8000000000000000,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0x8000000000000000,
 		},
 		{
 			input:      0x7ffffffffffffffe,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0x8000000000000000,
 		},
 		// neg max +- 1
 		{
 			input:      -0x8000000000000000,
 			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		{
 			input:      -0x8000000000000001,
 			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		{
 			input:      -0x7fffffffffffffff,
 			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		// trunc point +- 1
 		{
@@ -60,7 +63,7 @@ func TestFloatTruncation(t *testing.T) {
 		},
 		{
 			input:      0x7ffffffffffffe00,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0x8000000000000000,
 		},
 		{
@@ -72,48 +75,48 @@ func TestFloatTruncation(t *testing.T) {
 		{
 			input:      -0x7ffffffffffffdff,
 			convInt64:  -0x7ffffffffffffc00,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		{
 			input:      -0x7ffffffffffffe00,
 			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		{
 			input:      -0x7ffffffffffffdfe,
 			convInt64:  -0x7ffffffffffffc00,
-			convUInt64: 0x8000000000000000,
+			convUInt64: 0,
 		},
 		// umax +- 1
 		{
 			input:      0xffffffffffffffff,
-			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
+			convUInt64: 0xffffffffffffffff,
 		},
 		{
 			input:      0x10000000000000000,
-			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
+			convUInt64: 0xffffffffffffffff,
 		},
 		{
 			input:      0xfffffffffffffffe,
-			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
+			convUInt64: 0xffffffffffffffff,
 		},
 		// umax trunc +- 1
 		{
 			input:      0xfffffffffffffbff,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0xfffffffffffff800,
 		},
 		{
 			input:      0xfffffffffffffc00,
-			convInt64:  -0x8000000000000000,
-			convUInt64: 0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
+			convUInt64: 0xffffffffffffffff,
 		},
 		{
 			input:      0xfffffffffffffbfe,
-			convInt64:  -0x8000000000000000,
+			convInt64:  0x7fffffffffffffff,
 			convUInt64: 0xfffffffffffff800,
 		},
 	}

src/runtime/sys_wasm.s

@@ -22,64 +22,6 @@ TEXT runtime·wasmDiv(SB), NOSPLIT, $0-0
 	I64DivS
 	Return
 
-TEXT runtime·wasmTruncS(SB), NOSPLIT, $0-0
-	Get R0
-	Get R0
-	F64Ne // NaN
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	F64Const $0x7ffffffffffffc00p0 // Maximum truncated representation of 0x7fffffffffffffff
-	F64Gt
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	F64Const $-0x7ffffffffffffc00p0 // Minimum truncated representation of -0x8000000000000000
-	F64Lt
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	I64TruncF64S
-	Return
-
-TEXT runtime·wasmTruncU(SB), NOSPLIT, $0-0
-	Get R0
-	Get R0
-	F64Ne // NaN
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	F64Const $0xfffffffffffff800p0 // Maximum truncated representation of 0xffffffffffffffff
-	F64Gt
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	F64Const $0.
-	F64Lt
-	If
-		I64Const $0x8000000000000000
-		Return
-	End
-
-	Get R0
-	I64TruncF64U
-	Return
-
 TEXT runtime·exitThread(SB), NOSPLIT, $0-0
 	UNDEF