[PATCH] [clang/asan] Do not emit memcpy for trivial operator= when -fsanitize-address-field-padding >= 1

[Kostya Serebryany]

Hi majnemer, rsmith,

If we've added poisoned paddings to a type do not emit memcpy for operator=.

http://reviews.llvm.org/D6160

Files:
  lib/CodeGen/CGExprCXX.cpp
  test/CodeGen/sanitize-address-field-padding.cpp

Index: test/CodeGen/sanitize-address-field-padding.cpp
===================================================================
--- test/CodeGen/sanitize-address-field-padding.cpp
+++ test/CodeGen/sanitize-address-field-padding.cpp
@@ -217,3 +217,22 @@
 // WITH_CTOR_ALIASES-NOT: call void @_ZN15WithVirtualDtorD2Ev
 // WITH_CTOR_ALIASES: call void @_ZN28InheritsFrom_WithVirtualDtorD2Ev
 // WITH_CTOR_ALIASES: ret void
+//
+
+// Make sure we don't emit memcpy for operator= if paddings are inserted.
+struct ClassWithTrivialCopy {
+  ClassWithTrivialCopy();
+  ~ClassWithTrivialCopy();
+  void *a;
+ private:
+  void *c;
+};
+
+void MakeTrivialCopy(ClassWithTrivialCopy *s1, ClassWithTrivialCopy *s2) {
+  *s1 = *s2;
+}
+
+// CHECK-LABEL: define void @_Z15MakeTrivialCopyP20ClassWithTrivialCopyS0_
+// CHECK-NOT: memcpy
+// CHECK: ret void
+
Index: lib/CodeGen/CGExprCXX.cpp
===================================================================
--- lib/CodeGen/CGExprCXX.cpp
+++ lib/CodeGen/CGExprCXX.cpp
@@ -318,7 +318,7 @@
   llvm::Value *This = LV.getAddress();
 
   if ((MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator()) &&
-      MD->isTrivial()) {
+      MD->isTrivial() && !MD->getParent()->mayInsertExtraPadding()) {
     llvm::Value *Src = EmitLValue(E->getArg(1)).getAddress();
     QualType Ty = E->getType();
     EmitAggregateAssign(This, Src, Ty);

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