cmd/compile: make wasm match other platforms for FP->int32/64 conversions

this change is for overflows, so that all the platforms agree.

Change-Id: I9f459353615bf24ef8a5de641063d9ce34986241
Reviewed-on: https://go-review.googlesource.com/c/go/+/708358
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Keith Randall <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: dr2chase

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

@@ -76,13 +76,14 @@
 (Cvt32Uto(64|32)F x) => (F(64|32)ConvertI64U (ZeroExt32to64 x))
 (Cvt64Uto(64|32)F ...) => (F(64|32)ConvertI64U ...)
 
-(Cvt32Fto32 ...) => (I64TruncSatF32S ...)
+(Cvt32Fto32 ...) => (I32TruncSatF32S ...)
 (Cvt32Fto64 ...) => (I64TruncSatF32S ...)
-(Cvt64Fto32 ...) => (I64TruncSatF64S ...)
+(Cvt64Fto32 ...) => (I32TruncSatF64S ...)
 (Cvt64Fto64 ...) => (I64TruncSatF64S ...)
-(Cvt32Fto32U ...) => (I64TruncSatF32U ...)
+
+(Cvt32Fto32U ...) => (I32TruncSatF32U ...)
 (Cvt32Fto64U ...) => (I64TruncSatF32U ...)
-(Cvt64Fto32U ...) => (I64TruncSatF64U ...)
+(Cvt64Fto32U ...) => (I32TruncSatF64U ...)
 (Cvt64Fto64U ...) => (I64TruncSatF64U ...)
 
 (Cvt32Fto64F ...) => (F64PromoteF32 ...)

src/cmd/compile/internal/ssa/_gen/WasmOps.go

@@ -222,10 +222,19 @@ func init() {
 		{name: "F64Mul", asm: "F64Mul", argLength: 2, reg: fp64_21, typ: "Float64"}, // arg0 * arg1
 		{name: "F64Div", asm: "F64Div", argLength: 2, reg: fp64_21, typ: "Float64"}, // arg0 / arg1
 
-		{name: "I64TruncSatF64S", asm: "I64TruncSatF64S", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to a signed integer (saturating)
-		{name: "I64TruncSatF64U", asm: "I64TruncSatF64U", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to an unsigned integer (saturating)
-		{name: "I64TruncSatF32S", asm: "I64TruncSatF32S", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to a signed integer (saturating)
-		{name: "I64TruncSatF32U", asm: "I64TruncSatF32U", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Int64"}, // truncates the float arg0 to an unsigned integer (saturating)
+		{name: "I64TruncSatF64S", asm: "I64TruncSatF64S", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Int64"},  // truncates the float arg0 to a signed integer (saturating)
+		{name: "I64TruncSatF64U", asm: "I64TruncSatF64U", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Uint64"}, // truncates the float arg0 to an unsigned integer (saturating)
+		{name: "I64TruncSatF32S", asm: "I64TruncSatF32S", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Int64"},  // truncates the float arg0 to a signed integer (saturating)
+		{name: "I64TruncSatF32U", asm: "I64TruncSatF32U", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Uint64"}, // truncates the float arg0 to an unsigned integer (saturating)
+
+		// It appears to be wasm convention that everything lands in a 64-bit register;
+		// the WASM instructions for these operations produce 32-bit width results, but
+		// wasm/ssa.go widens them appropriately to 64-bit results.
+		{name: "I32TruncSatF64S", asm: "I32TruncSatF64S", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Int64"},  // truncates the float arg0 to a signed integer (saturating)
+		{name: "I32TruncSatF64U", asm: "I32TruncSatF64U", argLength: 1, reg: regInfo{inputs: []regMask{fp64}, outputs: []regMask{gp}}, typ: "Uint64"}, // truncates the float arg0 to an unsigned integer (saturating)
+		{name: "I32TruncSatF32S", asm: "I32TruncSatF32S", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Int64"},  // truncates the float arg0 to a signed integer (saturating)
+		{name: "I32TruncSatF32U", asm: "I32TruncSatF32U", argLength: 1, reg: regInfo{inputs: []regMask{fp32}, outputs: []regMask{gp}}, typ: "Uint64"}, // truncates the float arg0 to an unsigned integer (saturating)
+
 		{name: "F32ConvertI64S", asm: "F32ConvertI64S", argLength: 1, reg: regInfo{inputs: []regMask{gp}, outputs: []regMask{fp32}}, typ: "Float32"}, // converts the signed integer arg0 to a float
 		{name: "F32ConvertI64U", asm: "F32ConvertI64U", argLength: 1, reg: regInfo{inputs: []regMask{gp}, outputs: []regMask{fp32}}, typ: "Float32"}, // converts the unsigned integer arg0 to a float
 		{name: "F64ConvertI64S", asm: "F64ConvertI64S", argLength: 1, reg: regInfo{inputs: []regMask{gp}, outputs: []regMask{fp64}}, typ: "Float64"}, // converts the signed integer arg0 to a float

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

@@ -430,6 +430,17 @@ func ssaGenValueOnStack(s *ssagen.State, v *ssa.Value, extend bool) {
 		getValue64(s, v.Args[0])
 		s.Prog(v.Op.Asm())
 
+		// 32-bit integer conversion results
+	case ssa.OpWasmI32TruncSatF32S, ssa.OpWasmI32TruncSatF64S:
+		getValue64(s, v.Args[0])
+		s.Prog(v.Op.Asm())
+		s.Prog(wasm.AI64ExtendI32S)
+
+	case ssa.OpWasmI32TruncSatF32U, ssa.OpWasmI32TruncSatF64U:
+		getValue64(s, v.Args[0])
+		s.Prog(v.Op.Asm())
+		s.Prog(wasm.AI64ExtendI32U)
+
 	case ssa.OpWasmF32DemoteF64:
 		getValue64(s, v.Args[0])
 		s.Prog(v.Op.Asm())

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

@@ -4,11 +4,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build !wasm
-
-// TODO fix this to work for wasm
-// Doing more than this, however, expands the change.
-
 package main
 
 import (