Fix a bug in GetKnownAlignment of packed structs.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40649 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 06a67493750ca0507afda0059dd12b2e02db5adc..a7e817a8e6540c57f150c5c680b97ee9df1bb33d 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -7533,11 +7533,13 @@ static unsigned GetKnownAlignment(Value *V, TargetData *TD) {
 
     const Type *BasePtrTy = GEPI->getOperand(0)->getType();
     const PointerType *PtrTy = cast<PointerType>(BasePtrTy);
-    if (TD->getABITypeAlignment(PtrTy->getElementType())
-        <= BaseAlignment) {
+    unsigned Align = TD->getABITypeAlignment(PtrTy->getElementType());
+    if (Align <= BaseAlignment) {
       const Type *GEPTy = GEPI->getType();
       const PointerType *GEPPtrTy = cast<PointerType>(GEPTy);
-      return TD->getABITypeAlignment(GEPPtrTy->getElementType());
+      Align = std::min(Align, (unsigned)
+                       TD->getABITypeAlignment(GEPPtrTy->getElementType()));
+      return Align;
     }
     return 0;
   }

diff --git a/test/Transforms/InstCombine/known_align.ll b/test/Transforms/InstCombine/known_align.ll
new file mode 100644 (file)
index 0000000..a6e3409
--- /dev/null
+++ b/test/Transforms/InstCombine/known_align.ll
@@ -0,0 +1,27 @@
+; RUN: llvm-as < %s | opt -instcombine | llvm-dis | grep {align 1}
+; END.
+
+       %struct.p = type <{ i8, i32 }>
+@t = global %struct.p <{ i8 1, i32 10 }>               ; <%struct.p*> [#uses=1]
+@u = weak global %struct.p zeroinitializer             ; <%struct.p*> [#uses=1]
+
+define i32 @main() {
+entry:
+       %retval = alloca i32, align 4           ; <i32*> [#uses=2]
+       %tmp = alloca i32, align 4              ; <i32*> [#uses=2]
+       %tmp1 = alloca i32, align 4             ; <i32*> [#uses=3]
+       %"alloca point" = bitcast i32 0 to i32          ; <i32> [#uses=0]
+       %tmp3 = load i32* getelementptr (%struct.p* @t, i32 0, i32 1), align 1          ; <i32> [#uses=1]
+       store i32 %tmp3, i32* %tmp1, align 4
+       %tmp5 = load i32* %tmp1, align 4                ; <i32> [#uses=1]
+       store i32 %tmp5, i32* getelementptr (%struct.p* @u, i32 0, i32 1), align 1
+       %tmp6 = load i32* %tmp1, align 4                ; <i32> [#uses=1]
+       store i32 %tmp6, i32* %tmp, align 4
+       %tmp7 = load i32* %tmp, align 4         ; <i32> [#uses=1]
+       store i32 %tmp7, i32* %retval, align 4
+       br label %return
+
+return:                ; preds = %entry
+       %retval8 = load i32* %retval            ; <i32> [#uses=1]
+       ret i32 %retval8
+}