Stack Alignment: throw error if we can't satisfy the minimal alignment

requirement when creating stack objects in MachineFrameInfo.

Add CreateStackObjectWithMinAlign to throw error when the minimal alignment
can't be achieved and to clamp the alignment when the preferred alignment
can't be achieved. Same is true for CreateVariableSizedObject.
Will not emit error in CreateSpillStackObject or CreateStackObject.

As long as callers of CreateStackObject do not assume the object will be
aligned at the requested alignment, we should not have miscompile since
later optimizations which look at the object's alignment will have the correct
information.

rdar://12713765

llvm-svn: 172027

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 8c22db35cb1..ee98b00e2b5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -3259,7 +3259,8 @@ void SelectionDAGBuilder::visitAlloca(const AllocaInst &I) {
 
   // Inform the Frame Information that we have just allocated a variable-sized
   // object.
-  FuncInfo.MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1);
+  FuncInfo.MF->getFrameInfo()->CreateVariableSizedObject(Align ? Align : 1,
+                                 I.getAlignment(), &I);
 }
 
 void SelectionDAGBuilder::visitLoad(const LoadInst &I) {