From: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Date: Thu, 5 Feb 2026 14:16:55 +0000 (+0700)
Subject: cmd/compile: fix SIMD type parameter instantiation
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=38ed6147485232f9562e87970c56f4491c082998;p=gostls13.git

cmd/compile: fix SIMD type parameter instantiation

When a SIMD type is used to instantiate a type parameter, the SIMD's
underlying type is its shape. This shape type must be marked as a SIMD
type, otherwise, the backend will confuse and does not know how to put
this SIMD type to proper registers.

Fixing this by marking a type as SIMD type if its underlying is already
a SIMD one.

Fixes #77444

Change-Id: I745c474469889c94bc68435472ba4820e9f752a1
Reviewed-on: https://go-review.googlesource.com/c/go/+/742320
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
---

diff --git a/src/cmd/compile/internal/types/type.go b/src/cmd/compile/internal/types/type.go
index 6663c49dd8..3fa0b90e12 100644
--- a/src/cmd/compile/internal/types/type.go
+++ b/src/cmd/compile/internal/types/type.go
@@ -1683,6 +1683,9 @@ func (t *Type) SetUnderlying(underlying *Type) {
 	if underlying.HasShape() {
 		t.SetHasShape(true)
 	}
+	if underlying.isSIMD {
+		simdify(t, underlying.isSIMDTag)
+	}
 
 	// spec: "The declared type does not inherit any methods bound
 	// to the existing type, but the method set of an interface
diff --git a/src/simd/archsimd/internal/simd_test/simd_test.go b/src/simd/archsimd/internal/simd_test/simd_test.go
index 36bde92455..b28b990ed5 100644
--- a/src/simd/archsimd/internal/simd_test/simd_test.go
+++ b/src/simd/archsimd/internal/simd_test/simd_test.go
@@ -1440,3 +1440,24 @@ func TestSaturateConcat(t *testing.T) {
 		})
 	}
 }
+
+func stringy[T interface{ String() string }](v T) string {
+	return v.String()
+}
+
+func double[T interface{ Add(T) T }](v T) T {
+	return v.Add(v)
+}
+
+// Test that vector type instantiation works correctly, see issue #77444.
+func TestTypeParam(t *testing.T) {
+	x := archsimd.LoadInt64x2Slice([]int64{1, 1})
+	y := archsimd.LoadInt64x2Slice([]int64{1, 1})
+	if got := stringy(x); got != y.String() {
+		t.Fatalf("string(x) = %q, want %q", got, y.String())
+	}
+	want := y.Add(y)
+	if got := double(x); got.NotEqual(want).ToBits() != 0 {
+		t.Fatalf("double(x) = %v, want %v", got, want)
+	}
+}