When "low alignment" is specified, then set the alignment of the aggregate's

store to 1. This allows code-gen to select a more appropriate alignment. If left
to zero, an alignment greater than the alignment of the pointer may be selected,
causing code-gen to use instructions which require an alignment greater than the
pointer guarantees.
<rdar://problem/11043589>

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152951 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 4fe4fa8a144743ffc841e7ceea239a3b7e04eeea..4455f1a0865bb35570eb3766fa3f1526d928152a 100644 (file)
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -623,7 +623,9 @@ static void BuildAggStore(CodeGenFunction &CGF, llvm::Value *Val,
         SI->setAlignment(1);
     }
   } else {
-    CGF.Builder.CreateStore(Val, DestPtr, DestIsVolatile);
+    llvm::StoreInst *SI = CGF.Builder.CreateStore(Val, DestPtr, DestIsVolatile);
+    if (LowAlignment)
+      SI->setAlignment(1);
   }
 }
 

diff --git a/test/CodeGenCXX/2012-03-16-StoreAlign.cpp b/test/CodeGenCXX/2012-03-16-StoreAlign.cpp
new file mode 100644 (file)
index 0000000..c2c7548
--- /dev/null
+++ b/test/CodeGenCXX/2012-03-16-StoreAlign.cpp
@@ -0,0 +1,36 @@
+// RUN: %clang_cc1 -emit-llvm -o - -triple x86_64-apple-darwin %s | FileCheck %s
+// <rdar://problem/11043589>
+
+struct Length {
+  Length(double v) {
+    m_floatValue = static_cast<float>(v);
+  }
+
+  bool operator==(const Length& o) const {
+    return getFloatValue() == o.getFloatValue();
+  }
+  bool operator!=(const Length& o) const { return !(*this == o); }
+private:
+  float getFloatValue() const {
+    return m_floatValue;
+  }
+  float m_floatValue;
+};
+
+
+struct Foo {
+  static Length inchLength(double inch);
+  static bool getPageSizeFromName(const Length &A) {
+    static const Length legalWidth = inchLength(8.5);
+    if (A != legalWidth) return true;
+    return false;
+  }
+};
+
+// CHECK: @_ZZN3Foo19getPageSizeFromNameERK6LengthE10legalWidth = linkonce_odr global %struct.Length zeroinitializer, align 4
+// CHECK: store float %call, float* getelementptr inbounds (%struct.Length* @_ZZN3Foo19getPageSizeFromNameERK6LengthE10legalWidth, i32 0, i32 0), align 1
+
+bool bar(Length &b) {
+  Foo f;
+  return f.getPageSizeFromName(b);
+}