[CodeGen] Pessimize aliasing for member unions (and may-alias) objects

Use the TBAA info of the omnipotent char for these objects.

Differential Revision: https://reviews.llvm.org/D33328


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@303851 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 45 insertions, 0 deletions

diff --git a/test/CodeGenCXX/union-tbaa2.cpp b/test/CodeGenCXX/union-tbaa2.cpp
new file mode 100644
index 0000000000..d3e37408c4
--- /dev/null
+++ b/test/CodeGenCXX/union-tbaa2.cpp
@@ -0,0 +1,45 @@
+// RUN: %clang_cc1 %s -O2 -std=c++11 -triple x86_64-unknown-linux-gnu -target-cpu x86-64 -target-feature +sse4.2 -target-feature +avx -emit-llvm -o - | FileCheck %s
+
+// Testcase from llvm.org/PR32056
+
+extern "C" int printf (const char *__restrict __format, ...);
+
+typedef double __m256d __attribute__((__vector_size__(32)));
+
+static __inline __m256d __attribute__((__always_inline__, __nodebug__,
+                                       __target__("avx")))
+_mm256_setr_pd(double __a, double __b, double __c, double __d) {
+  return (__m256d){ __a, __b, __c, __d };
+}
+
+struct A {
+  A () {
+// Check that the TBAA information generated for the stores to the
+// union members is based on the omnipotent char.
+// CHECK: store <4 x double>
+// CHECK: tbaa ![[OCPATH:[0-9]+]]
+// CHECK: store <4 x double>
+// CHECK: tbaa ![[OCPATH]]
+// CHECK: call
+    a = _mm256_setr_pd(0.0, 1.0, 2.0, 3.0);
+    b = _mm256_setr_pd(4.0, 5.0, 6.0, 7.0);
+  }
+
+  const double *begin() { return c; }
+  const double *end() { return c+8; }
+
+  union {
+    struct { __m256d a, b; };
+    double c[8];
+  };
+};
+
+int main(int argc, char *argv[]) {
+  A a;
+  for (double value : a)
+    printf("%f ", value);
+  return 0;
+}
+
+// CHECK-DAG: ![[CHAR:[0-9]+]] = !{!"omnipotent char"
+// CHECK-DAG: ![[OCPATH]] = !{![[CHAR]], ![[CHAR]], i64 0}