When emitting a compound literal of POD type, continue to emit a

separate aggregate temporary and then memcpy it over to the
destination. This fixes a regression I introduced with r133235, where
the compound literal on the RHS of an assignment makes use of the
structure on the LHS of the assignment.

I'm deeply suspicious of AggExprEmitter::VisitBinAssign()'s
optimization where it emits the RHS of an aggregate assignment
directly into the LHS lvalue without checking whether there is any
aliasing between the LHS/RHS. However, I'm not in a position to
revisit this now.

Big thanks to Eli for finding the regression!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133261 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index 694316983e..b1ac731f21 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -247,6 +247,16 @@ void AggExprEmitter::VisitOpaqueValueExpr(OpaqueValueExpr *e) {
 
 void
 AggExprEmitter::VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
+  if (E->getType().isPODType(CGF.getContext())) {
+    // For a POD type, just emit a load of the lvalue + a copy, because our
+    // compound literal might alias the destination.
+    // FIXME: This is a band-aid; the real problem appears to be in our handling
+    // of assignments, where we store directly into the LHS without checking
+    // whether anything in the RHS aliases.
+    EmitAggLoadOfLValue(E);
+    return;
+  }
+  
   AggValueSlot Slot = EnsureSlot(E->getType());
   CGF.EmitAggExpr(E->getInitializer(), Slot);
 }