[dev.simd] cmd/compile: make condtion of CanSSA smarter for SIMD fields

This CL tires to improve a situation pointed out by
https://github.com/golang/go/issues/73787#issuecomment-3305494947.

Change-Id: Ic23c80fe71344fc25383ab238ad6631e0f0cd22e
Reviewed-on: https://go-review.googlesource.com/c/go/+/705416
Reviewed-by: Cherry Mui <cherryyz@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

diff --git a/src/cmd/compile/internal/ssa/value.go b/src/cmd/compile/internal/ssa/value.go
index 4d0c4fb50f843cb8e50db38fb4b4773493045e33..3b9cadf6f18fa542fe9b5a06230507f207a9d3e0 100644 (file)
--- a/src/cmd/compile/internal/ssa/value.go
+++ b/src/cmd/compile/internal/ssa/value.go
@@ -9,6 +9,7 @@ import (
        "cmd/compile/internal/types"
        "cmd/internal/src"
        "fmt"
+       "internal/buildcfg"
        "math"
        "sort"
        "strings"
@@ -615,11 +616,14 @@ func CanSSA(t *types.Type) bool {
        if t.IsSIMD() {
                return true
        }
-       if t.Size() > int64(4*types.PtrSize) {
+       sizeLimit := int64(MaxStruct * types.PtrSize)
+       if t.Size() > sizeLimit {
                // 4*Widthptr is an arbitrary constant. We want it
                // to be at least 3*Widthptr so slices can be registerized.
                // Too big and we'll introduce too much register pressure.
-               return false
+               if !buildcfg.Experiment.SIMD {
+                       return false
+               }
        }
        switch t.Kind() {
        case types.TARRAY:
@@ -639,7 +643,17 @@ func CanSSA(t *types.Type) bool {
                                return false
                        }
                }
-               return true
+               // Special check for SIMD. If the composite type
+               // contains SIMD vectors we can return true
+               // if it pass the checks below.
+               if !buildcfg.Experiment.SIMD {
+                       return true
+               }
+               if t.Size() <= sizeLimit {
+                       return true
+               }
+               i, f := t.Registers()
+               return i+f <= MaxStruct
        default:
                return true
        }

diff --git a/src/cmd/compile/internal/test/value_test.go b/src/cmd/compile/internal/test/value_test.go
new file mode 100644 (file)
index 0000000..bb98f4f
--- /dev/null
+++ b/src/cmd/compile/internal/test/value_test.go
@@ -0,0 +1,41 @@
+// Copyright 2025 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package test
+
+import (
+       "cmd/compile/internal/ssa"
+       "cmd/compile/internal/types"
+       "internal/buildcfg"
+       "testing"
+)
+
+// This file contains tests for ssa values, types and their utility functions.
+
+func TestCanSSA(t *testing.T) {
+       i64 := types.Types[types.TINT64]
+       v128 := types.TypeVec128
+       s1 := mkstruct(i64, mkstruct(i64, i64, i64, i64))
+       if ssa.CanSSA(s1) {
+               // Test size check for struct.
+               t.Errorf("CanSSA(%v) returned true, expected false", s1)
+       }
+       a1 := types.NewArray(s1, 1)
+       if ssa.CanSSA(a1) {
+               // Test size check for array.
+               t.Errorf("CanSSA(%v) returned true, expected false", a1)
+       }
+       if buildcfg.Experiment.SIMD {
+               s2 := mkstruct(v128, v128, v128, v128)
+               if !ssa.CanSSA(s2) {
+                       // Test size check for SIMD struct special case.
+                       t.Errorf("CanSSA(%v) returned false, expected true", s2)
+               }
+               a2 := types.NewArray(s2, 1)
+               if !ssa.CanSSA(a2) {
+                       // Test size check for SIMD array special case.
+                       t.Errorf("CanSSA(%v) returned false, expected true", a2)
+               }
+       }
+}

diff --git a/test/codegen/simd.go b/test/codegen/simd.go
index 0d617bfc462004f438c7b71064c2ed5fe3ef8134..91f4291c932609840c7af368d08ae52914db5327 100644 (file)
--- a/test/codegen/simd.go
+++ b/test/codegen/simd.go
@@ -27,3 +27,33 @@ func vptest2() bool {
        // amd64:`SETEQ\s(.*)$`
        return v1.And(v2).IsZero()
 }
+
+type Args2 struct {
+       V0 simd.Uint8x32
+       V1 simd.Uint8x32
+       x  string
+}
+
+//go:noinline
+func simdStructNoSpill(a Args2) simd.Uint8x32 {
+       // amd64:-`VMOVDQU\s.*$`
+       return a.V0.Xor(a.V1)
+}
+
+func simdStructWrapperNoSpill(a Args2) simd.Uint8x32 {
+       // amd64:-`VMOVDQU\s.*$`
+       a.x = "test"
+       return simdStructNoSpill(a)
+}
+
+//go:noinline
+func simdArrayNoSpill(a [1]Args2) simd.Uint8x32 {
+       // amd64:-`VMOVDQU\s.*$`
+       return a[0].V0.Xor(a[0].V1)
+}
+
+func simdArrayWrapperNoSpill(a [1]Args2) simd.Uint8x32 {
+       // amd64:-`VMOVDQU\s.*$`
+       a[0].x = "test"
+       return simdArrayNoSpill(a)
+}