Fix an invalid bitcast crash that occurs when doing a partial memset of a vector

alloca. Fixes part of <rdar://problem/9580800>.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@133336 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Scalar/ScalarReplAggregates.cpp

@@ -521,10 +521,22 @@ bool ConvertToScalarInfo::CanConvertToScalar(Value *V, uint64_t Offset) {
     // If this is a constant sized memset of a constant value (e.g. 0) we can
     // handle it.
     if (MemSetInst *MSI = dyn_cast<MemSetInst>(User)) {
-      // Store of constant value and constant size.
+      // Store of constant value.
-      if (!isa<ConstantInt>(MSI->getValue()) ||
+      if (!isa<ConstantInt>(MSI->getValue()))
-          !isa<ConstantInt>(MSI->getLength()))
         return false;
+
+      // Store of constant size.
+      ConstantInt *Len = dyn_cast<ConstantInt>(MSI->getLength());
+      if (!Len)
+        return false;
+
+      // If the size differs from the alloca, we can only convert the alloca to
+      // an integer bag-of-bits.
+      // FIXME: This should handle all of the cases that are currently accepted
+      // as vector element insertions.
+      if (Len->getZExtValue() != AllocaSize || Offset != 0)
+        ScalarKind = Integer;
+
       IsNotTrivial = true;  // Can't be mem2reg'd.
       HadNonMemTransferAccess = true;
       continue;

test/Transforms/ScalarRepl/2011-06-17-VectorPartialMemset.ll

@@ -0,0 +1,22 @@
+; RUN: opt < %s -scalarrepl -S | FileCheck %s
+target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:32:64-v128:32:128-a0:0:32-n32"
+target triple = "thumbv7-apple-darwin10"
+
+; CHECK: f
+; CHECK-NOT: alloca
+; CHECK: %[[A:[a-z0-9]*]] = and i128 undef, -16777216
+; CHECK: %[[B:[a-z0-9]*]] = bitcast i128 %[[A]] to <4 x float>
+; CHECK: %[[C:[a-z0-9]*]] = extractelement <4 x float> %[[B]], i32 0
+; CHECK: ret float %[[C]]
+
+define float @f() nounwind ssp {
+entry:
+  %a = alloca <4 x float>, align 16
+  %p = bitcast <4 x float>* %a to i8*
+  call void @llvm.memset.p0i8.i32(i8* %p, i8 0, i32 3, i32 16, i1 false)
+  %vec = load <4 x float>* %a, align 8
+  %val = extractelement <4 x float> %vec, i32 0
+  ret float %val
+}
+
+declare void @llvm.memset.p0i8.i32(i8* nocapture, i8, i32, i32, i1) nounwind