This just in, it is a *bad idea* to use 'udiv' on an offset of

a pointer. A very bad idea. Let's not do that. Fixes PR14105.

Note that this wasn't *that* glaring of an oversight. Originally, these
routines were only called on offsets within an alloca, which are
intrinsically positive. But over the evolution of the pass, they ended
up being called for arbitrary offsets, and things went downhill...

llvm-svn: 166095

1 files changed, 3 insertions, 3 deletions

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index e2078b4b448..f3501cd7d56 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -1828,7 +1828,7 @@ static Value *getNaturalGEPRecursively(IRBuilder<> &IRB, const DataLayout &TD,
     if (ElementSizeInBits % 8)
       return 0; // GEPs over non-multiple of 8 size vector elements are invalid.
     APInt ElementSize(Offset.getBitWidth(), ElementSizeInBits / 8);
-    APInt NumSkippedElements = Offset.udiv(ElementSize);
+    APInt NumSkippedElements = Offset.sdiv(ElementSize);
     if (NumSkippedElements.ugt(VecTy->getNumElements()))
       return 0;
     Offset -= NumSkippedElements * ElementSize;
@@ -1840,7 +1840,7 @@ static Value *getNaturalGEPRecursively(IRBuilder<> &IRB, const DataLayout &TD,
   if (ArrayType *ArrTy = dyn_cast<ArrayType>(Ty)) {
     Type *ElementTy = ArrTy->getElementType();
     APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
-    APInt NumSkippedElements = Offset.udiv(ElementSize);
+    APInt NumSkippedElements = Offset.sdiv(ElementSize);
     if (NumSkippedElements.ugt(ArrTy->getNumElements()))
       return 0;
 
@@ -1896,7 +1896,7 @@ static Value *getNaturalGEPWithOffset(IRBuilder<> &IRB, const DataLayout &TD,
   APInt ElementSize(Offset.getBitWidth(), TD.getTypeAllocSize(ElementTy));
   if (ElementSize == 0)
     return 0; // Zero-length arrays can't help us build a natural GEP.
-  APInt NumSkippedElements = Offset.udiv(ElementSize);
+  APInt NumSkippedElements = Offset.sdiv(ElementSize);
 
   Offset -= NumSkippedElements * ElementSize;
   Indices.push_back(IRB.getInt(NumSkippedElements));