Fix assert with GEP ptr vector indexing structs

Also fix it calculating the wrong value. The struct index
is not a ConstantInt, so it was being interpreted as an array
index.

llvm-svn: 188713

1 files changed, 12 insertions, 2 deletions

diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 6e38061aa52..c81537543f5 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -629,9 +629,19 @@ void llvm::ComputeMaskedBits(Value *V, APInt &KnownZero, APInt &KnownOne,
       Value *Index = I->getOperand(i);
       if (StructType *STy = dyn_cast<StructType>(*GTI)) {
         // Handle struct member offset arithmetic.
-        if (!TD) return;
-        const StructLayout *SL = TD->getStructLayout(STy);
+        if (!TD)
+          return;
+
+        // Handle case when index is vector zeroinitializer
+        Constant *CIndex = cast<Constant>(Index);
+        if (CIndex->isZeroValue())
+          continue;
+
+        if (CIndex->getType()->isVectorTy())
+          Index = CIndex->getSplatValue();
+
         unsigned Idx = cast<ConstantInt>(Index)->getZExtValue();
+        const StructLayout *SL = TD->getStructLayout(STy);
         uint64_t Offset = SL->getElementOffset(Idx);
         TrailZ = std::min<unsigned>(TrailZ,
                                     countTrailingZeros(Offset));