Merging r260587:

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r260587 | pete | 2016-02-11 13:10:40 -0800 (Thu, 11 Feb 2016) | 13 lines

Set load alignment on aggregate loads.

When optimizing a extractvalue(load), we generate a load from the
aggregate type.  This load didn't have alignment set and so would
get the alignment of the type.  This breaks when the type is packed
and so the alignment should be lower.

For example, loading { int, int } would give us alignment of 4, but
the original load from this type may have an alignment of 1 if packed.

Reviewed by David Majnemer

Differential revision: http://reviews.llvm.org/D17158
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_38@260640 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
index 47406b9a1632086d6e30e35b3a7c99da061002a5..dd2889de405e0561fdde4c04ca70bf0788c9c193 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
+++ b/lib/Transforms/InstCombine/InstCombineLoadStoreAlloca.cpp
@@ -557,7 +557,8 @@ static Instruction *unpackLoadToAggregate(InstCombiner &IC, LoadInst &LI) {
         ConstantInt::get(IdxType, i),
       };
       auto *Ptr = IC.Builder->CreateInBoundsGEP(ST, Addr, makeArrayRef(Indices), EltName);
-      auto *L = IC.Builder->CreateLoad(ST->getTypeAtIndex(i), Ptr, LoadName);
+      auto *L = IC.Builder->CreateAlignedLoad(Ptr, LI.getAlignment(),
+                                              LoadName);
       V = IC.Builder->CreateInsertValue(V, L, i);
     }
 

diff --git a/test/Transforms/InstCombine/unpack-fca.ll b/test/Transforms/InstCombine/unpack-fca.ll
index 9b8d104574914b6ce0f8141a805982f77bacaa95..435983924b77aa453d7cd46c2bea1d055fbd3162 100644 (file)
--- a/test/Transforms/InstCombine/unpack-fca.ll
+++ b/test/Transforms/InstCombine/unpack-fca.ll
@@ -136,3 +136,18 @@ define %B @structB(%B* %b.ptr) {
   %1 = load %B, %B* %b.ptr, align 8
   ret %B %1
 }
+
+%struct.S = type <{ i8, %struct.T }>
+%struct.T = type { i32, i32 }
+
+; Make sure that we do not increase alignment of packed struct element
+define i32 @packed_alignment(%struct.S* dereferenceable(9) %s) {
+; CHECK-LABEL: packed_alignment
+; CHECK-NEXT: %tv.elt1 = getelementptr inbounds %struct.S, %struct.S* %s, i64 0, i32 1, i32 1
+; CHECK-NEXT: %tv.unpack2 = load i32, i32* %tv.elt1, align 1
+; CHECK-NEXT: ret i32 %tv.unpack2
+  %t = getelementptr inbounds %struct.S, %struct.S* %s, i32 0, i32 1
+  %tv = load %struct.T, %struct.T* %t, align 1
+  %v = extractvalue %struct.T %tv, 1
+  ret i32 %v
+}