[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

2 files changed, 31 insertions, 10 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};
diff --git a/llvm/test/Transforms/ArgumentPromotion/byval.ll b/llvm/test/Transforms/ArgumentPromotion/byval.ll
index 58475fc8960..00542e3ec24 100644
--- a/llvm/test/Transforms/ArgumentPromotion/byval.ll
+++ b/llvm/test/Transforms/ArgumentPromotion/byval.ll
@@ -6,24 +6,45 @@ target datalayout = "E-p:64:64:64-a0:0:8-f32:32:32-f64:64:64-i1:8:8-i8:8:8-i16:1
 %struct.ss = type { i32, i64 }
 
 define internal void @f(%struct.ss* byval  %b) nounwind  {
+entry:
+  %tmp = getelementptr %struct.ss, %struct.ss* %b, i32 0, i32 0
+  %tmp1 = load i32, i32* %tmp, align 4
+  %tmp2 = add i32 %tmp1, 1
+  store i32 %tmp2, i32* %tmp, align 4
+  ret void
+}
+
 ; CHECK-LABEL: define internal void @f(i32 %b.0, i64 %b.1)
+; CHECK: alloca %struct.ss{{$}}
+; CHECK: store i32 %b.0
+; CHECK: store i64 %b.1
+
+define internal void @g(%struct.ss* byval align 32 %b) nounwind {
 entry:
-  %tmp = getelementptr %struct.ss, %struct.ss* %b, i32 0, i32 0		; <i32*> [#uses=2]
-  %tmp1 = load i32, i32* %tmp, align 4		; <i32> [#uses=1]
-  %tmp2 = add i32 %tmp1, 1		; <i32> [#uses=1]
+  %tmp = getelementptr %struct.ss, %struct.ss* %b, i32 0, i32 0
+  %tmp1 = load i32, i32* %tmp, align 4
+  %tmp2 = add i32 %tmp1, 1
   store i32 %tmp2, i32* %tmp, align 4
   ret void
 }
 
+; CHECK-LABEL: define internal void @g(i32 %b.0, i64 %b.1)
+; CHECK: alloca %struct.ss, align 32
+; CHECK: store i32 %b.0
+; CHECK: store i64 %b.1
+
 define i32 @main() nounwind  {
-; CHECK-LABEL: define i32 @main
 entry:
-  %S = alloca %struct.ss		; <%struct.ss*> [#uses=4]
-  %tmp1 = getelementptr %struct.ss, %struct.ss* %S, i32 0, i32 0		; <i32*> [#uses=1]
+  %S = alloca %struct.ss
+  %tmp1 = getelementptr %struct.ss, %struct.ss* %S, i32 0, i32 0
   store i32 1, i32* %tmp1, align 8
-  %tmp4 = getelementptr %struct.ss, %struct.ss* %S, i32 0, i32 1		; <i64*> [#uses=1]
+  %tmp4 = getelementptr %struct.ss, %struct.ss* %S, i32 0, i32 1
   store i64 2, i64* %tmp4, align 4
-  call void @f( %struct.ss* byval  %S ) nounwind 
-; CHECK: call void @f(i32 %{{.*}}, i64 %{{.*}})
+  call void @f(%struct.ss* byval %S) nounwind
+  call void @g(%struct.ss* byval %S) nounwind
   ret i32 0
 }
+
+; CHECK-LABEL: define i32 @main
+; CHECK: call void @f(i32 %{{.*}}, i64 %{{.*}})
+; CHECK: call void @g(i32 %{{.*}}, i64 %{{.*}})