[llvm-commits] [llvm] r160589 - in /llvm/trunk: include/llvm/Transforms/Utils/Local.h lib/Analysis/MemoryBuiltins.cpp test/Instrumentation/BoundsChecking/simple.ll

[Nuno Lopes]

Author: nlopes
Date: Fri Jul 20 18:07:40 2012
New Revision: 160589

URL: http://llvm.org/viewvc/llvm-project?rev=160589&view=rev
Log:
baby steps toward fixing some problems with inbound GEPs that overflow, as discussed 2 months ago or so.
Make sure we do not emit index computations with NSW flags so that we dont get an undef value if the GEP overflows

Modified:
    llvm/trunk/include/llvm/Transforms/Utils/Local.h
    llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
    llvm/trunk/test/Instrumentation/BoundsChecking/simple.ll

Modified: llvm/trunk/include/llvm/Transforms/Utils/Local.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Transforms/Utils/Local.h?rev=160589&r1=160588&r2=160589&view=diff
==============================================================================
--- llvm/trunk/include/llvm/Transforms/Utils/Local.h (original)
+++ llvm/trunk/include/llvm/Transforms/Utils/Local.h Fri Jul 20 18:07:40 2012
@@ -168,15 +168,18 @@
 /// EmitGEPOffset - Given a getelementptr instruction/constantexpr, emit the
 /// code necessary to compute the offset from the base pointer (without adding
 /// in the base pointer).  Return the result as a signed integer of intptr size.
+/// When NoAssumptions is true, no assumptions about index computation not
+/// overflowing is made.
 template<typename IRBuilderTy>
-Value *EmitGEPOffset(IRBuilderTy *Builder, const TargetData &TD, User *GEP) {
+Value *EmitGEPOffset(IRBuilderTy *Builder, const TargetData &TD, User *GEP,
+                     bool NoAssumptions = false) {
   gep_type_iterator GTI = gep_type_begin(GEP);
   Type *IntPtrTy = TD.getIntPtrType(GEP->getContext());
   Value *Result = Constant::getNullValue(IntPtrTy);
 
   // If the GEP is inbounds, we know that none of the addressing operations will
   // overflow in an unsigned sense.
-  bool isInBounds = cast<GEPOperator>(GEP)->isInBounds();
+  bool isInBounds = cast<GEPOperator>(GEP)->isInBounds() && !NoAssumptions;
 
   // Build a mask for high order bits.
   unsigned IntPtrWidth = TD.getPointerSizeInBits();

Modified: llvm/trunk/lib/Analysis/MemoryBuiltins.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Analysis/MemoryBuiltins.cpp?rev=160589&r1=160588&r2=160589&view=diff
==============================================================================
--- llvm/trunk/lib/Analysis/MemoryBuiltins.cpp (original)
+++ llvm/trunk/lib/Analysis/MemoryBuiltins.cpp Fri Jul 20 18:07:40 2012
@@ -645,7 +645,7 @@
   if (!bothKnown(PtrData))
     return unknown();
 
-  Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP);
+  Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP, /*NoAssumptions=*/true);
   Offset = Builder.CreateAdd(PtrData.second, Offset);
   return std::make_pair(PtrData.first, Offset);
 }

Modified: llvm/trunk/test/Instrumentation/BoundsChecking/simple.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Instrumentation/BoundsChecking/simple.ll?rev=160589&r1=160588&r2=160589&view=diff
==============================================================================
--- llvm/trunk/test/Instrumentation/BoundsChecking/simple.ll (original)
+++ llvm/trunk/test/Instrumentation/BoundsChecking/simple.ll Fri Jul 20 18:07:40 2012
@@ -116,3 +116,13 @@
   %3 = load i8* %2, align 4
   ret void
 }
+
+; CHECK: @f12
+define i64 @f12(i64 %x, i64 %y) nounwind {
+  %1 = tail call i8* @calloc(i64 1, i64 %x)
+; CHECK: mul i64 %y, 8
+  %2 = bitcast i8* %1 to i64*
+  %3 = getelementptr inbounds i64* %2, i64 %y
+  %4 = load i64* %3, align 8
+  ret i64 %4
+}