[clang] [Clang] Freeze padded vectors before storing. (PR #164821)

[Florian Hahn via cfe-commits]

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@@ -0,0 +1,42 @@
+// NOTE: Assertions have been autogenerated by utils/update_cc_test_checks.py UTC_ARGS: --version 6
+// RUN: %clang_cc1 -fenable-matrix -triple arm64-apple-macosx %s -emit-llvm -disable-llvm-passes -o - | FileCheck %s
+
+typedef float float3 __attribute__((ext_vector_type(3)));
+struct Vec3 {
+  union {
+    struct {
+      float x;
+      float y;
+      float z;
+    };
+  float vec __attribute__((ext_vector_type(3)));
+  };
+};
+
+// CHECK-LABEL: define i128 @add(
+// CHECK-SAME: i128 [[A_COERCE:%.*]]) #[[ATTR0:[0-9]+]] {
+// CHECK-NEXT:  [[ENTRY:.*:]]
+// CHECK-NEXT:    [[RETVAL:%.*]] = alloca [[STRUCT_VEC3:%.*]], align 16
+// CHECK-NEXT:    [[A:%.*]] = alloca [[STRUCT_VEC3]], align 16
+// CHECK-NEXT:    [[COERCE_DIVE:%.*]] = getelementptr inbounds nuw [[STRUCT_VEC3]], ptr [[A]], i32 0, i32 0
+// CHECK-NEXT:    store i128 [[A_COERCE]], ptr [[COERCE_DIVE]], align 16
+// CHECK-NEXT:    [[TMP0:%.*]] = getelementptr inbounds nuw [[STRUCT_VEC3]], ptr [[A]], i32 0, i32 0
+// CHECK-NEXT:    [[LOADVECN:%.*]] = load <4 x float>, ptr [[TMP0]], align 16
+// CHECK-NEXT:    [[EXTRACTVEC:%.*]] = shufflevector <4 x float> [[LOADVECN]], <4 x float> poison, <3 x i32> <i32 0, i32 1, i32 2>
+// CHECK-NEXT:    [[TMP1:%.*]] = getelementptr inbounds nuw [[STRUCT_VEC3]], ptr [[A]], i32 0, i32 0
+// CHECK-NEXT:    [[LOADVECN1:%.*]] = load <4 x float>, ptr [[TMP1]], align 16
+// CHECK-NEXT:    [[EXTRACTVEC2:%.*]] = shufflevector <4 x float> [[LOADVECN1]], <4 x float> poison, <3 x i32> <i32 0, i32 1, i32 2>
+// CHECK-NEXT:    [[ADD:%.*]] = fadd <3 x float> [[EXTRACTVEC]], [[EXTRACTVEC2]]
+// CHECK-NEXT:    [[TMP2:%.*]] = getelementptr inbounds nuw [[STRUCT_VEC3]], ptr [[RETVAL]], i32 0, i32 0
+// CHECK-NEXT:    [[EXTRACTVEC3:%.*]] = shufflevector <3 x float> [[ADD]], <3 x float> undef, <4 x i32> <i32 0, i32 1, i32 2, i32 poison>
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fhahn wrote:

My outdated understanding was that poison in a mask lane means any of the input lanes may be selected, not that the lane itself is poison. Updated to select the first undef lane, thanks

https://github.com/llvm/llvm-project/pull/164821