[ArgPromotion] Preserve alignment of byval argument in new alloca

The frontend may have requested a higher alignment for any reason, and
downstream optimizations may already have taken advantage of it.  We
should keep the same alignment when moving the allocation from the
parameter area to the local variable area.

Fixes PR34038

llvm-svn: 310071

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
index 53223ab4431..72bae203ee9 100644
--- a/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
+++ b/llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
@@ -356,7 +356,7 @@ doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote,
       // Just add all the struct element types.
       Type *AgTy = cast<PointerType>(I->getType())->getElementType();
       Value *TheAlloca = new AllocaInst(AgTy, DL.getAllocaAddrSpace(), nullptr,
-                                        "", InsertPt);
+                                        I->getParamAlignment(), "", InsertPt);
       StructType *STy = cast<StructType>(AgTy);
       Value *Idxs[2] = {ConstantInt::get(Type::getInt32Ty(F->getContext()), 0),
                         nullptr};