cmd/compile: (wasm) optimize float32(round64(float64(x)))

Not a fix because there are other architectures
still to be done.

Updates #75463.

Change-Id: Ia5233c2b6c5f4439e269950efdd851e72e8e7ff6
Reviewed-on: https://go-review.googlesource.com/c/go/+/730160
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

2 files changed, 120 insertions, 0 deletions

diff --git a/src/cmd/compile/internal/ssa/_gen/Wasm.rules b/src/cmd/compile/internal/ssa/_gen/Wasm.rules
index 6028152253..4b533df6a0 100644
--- a/src/cmd/compile/internal/ssa/_gen/Wasm.rules
+++ b/src/cmd/compile/internal/ssa/_gen/Wasm.rules
@@ -349,6 +349,9 @@
 (Abs ...) => (F64Abs ...)
 (Copysign ...) => (F64Copysign ...)
 
+(F32DemoteF64 (F64(Sqrt|Trunc|Ceil|Floor|Nearest|Abs) (F64PromoteF32 x))) => (F32(Sqrt|Trunc|Ceil|Floor|Nearest|Abs) x)
+(F32DemoteF64 (F64Copysign (F64PromoteF32 x) (F64PromoteF32 y))) => (F32Copysign x y)
+
 (Sqrt32 ...) => (F32Sqrt ...)
 
 (Ctz64 ...) => (I64Ctz ...)
diff --git a/src/cmd/compile/internal/ssa/rewriteWasm.go b/src/cmd/compile/internal/ssa/rewriteWasm.go
index faba41b3e5..f7fe8fa7e2 100644
--- a/src/cmd/compile/internal/ssa/rewriteWasm.go
+++ b/src/cmd/compile/internal/ssa/rewriteWasm.go
@@ -599,6 +599,8 @@ func rewriteValueWasm(v *Value) bool {
 	case OpWB:
 		v.Op = OpWasmLoweredWB
 		return true
+	case OpWasmF32DemoteF64:
+		return rewriteValueWasm_OpWasmF32DemoteF64(v)
 	case OpWasmF64Add:
 		return rewriteValueWasm_OpWasmF64Add(v)
 	case OpWasmF64Mul:
@@ -3617,6 +3619,121 @@ func rewriteValueWasm_OpStore(v *Value) bool {
 	}
 	return false
 }
+func rewriteValueWasm_OpWasmF32DemoteF64(v *Value) bool {
+	v_0 := v.Args[0]
+	// match: (F32DemoteF64 (F64Sqrt (F64PromoteF32 x)))
+	// result: (F32Sqrt x)
+	for {
+		if v_0.Op != OpWasmF64Sqrt {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Sqrt)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Trunc (F64PromoteF32 x)))
+	// result: (F32Trunc x)
+	for {
+		if v_0.Op != OpWasmF64Trunc {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Trunc)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Ceil (F64PromoteF32 x)))
+	// result: (F32Ceil x)
+	for {
+		if v_0.Op != OpWasmF64Ceil {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Ceil)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Floor (F64PromoteF32 x)))
+	// result: (F32Floor x)
+	for {
+		if v_0.Op != OpWasmF64Floor {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Floor)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Nearest (F64PromoteF32 x)))
+	// result: (F32Nearest x)
+	for {
+		if v_0.Op != OpWasmF64Nearest {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Nearest)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Abs (F64PromoteF32 x)))
+	// result: (F32Abs x)
+	for {
+		if v_0.Op != OpWasmF64Abs {
+			break
+		}
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v.reset(OpWasmF32Abs)
+		v.AddArg(x)
+		return true
+	}
+	// match: (F32DemoteF64 (F64Copysign (F64PromoteF32 x) (F64PromoteF32 y)))
+	// result: (F32Copysign x y)
+	for {
+		if v_0.Op != OpWasmF64Copysign {
+			break
+		}
+		_ = v_0.Args[1]
+		v_0_0 := v_0.Args[0]
+		if v_0_0.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		x := v_0_0.Args[0]
+		v_0_1 := v_0.Args[1]
+		if v_0_1.Op != OpWasmF64PromoteF32 {
+			break
+		}
+		y := v_0_1.Args[0]
+		v.reset(OpWasmF32Copysign)
+		v.AddArg2(x, y)
+		return true
+	}
+	return false
+}
 func rewriteValueWasm_OpWasmF64Add(v *Value) bool {
 	v_1 := v.Args[1]
 	v_0 := v.Args[0]