Remove the folding rule

  getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1) 
  to
  inttoptr (i64 0 to i8*)
from the VMCore constant folder. It didn't handle sign-extension properly
in the case where the source integer is smaller than a pointer size. And,
it relied on an assumption about sizeof(i8).

The Analysis constant folder still folds these kinds of things; it has
access to TargetData, so it can do them right.

Add a testcase which tests that the VMCore constant folder doesn't
miscompile this, and that the Analysis folder does fold it.

llvm-svn: 94750

1 files changed, 0 insertions, 22 deletions

diff --git a/llvm/lib/VMCore/ConstantFold.cpp b/llvm/lib/VMCore/ConstantFold.cpp
index 24b78ae969a..40061ee3d7b 100644
--- a/llvm/lib/VMCore/ConstantFold.cpp
+++ b/llvm/lib/VMCore/ConstantFold.cpp
@@ -2021,28 +2021,6 @@ Constant *llvm::ConstantFoldGetElementPtr(LLVMContext &Context,
                 ConstantExpr::getGetElementPtr(
                       (Constant*)CE->getOperand(0), Idxs, NumIdx);
     }
-
-    // Fold: getelementptr (i8* inttoptr (i64 1 to i8*), i32 -1)
-    // Into: inttoptr (i64 0 to i8*)
-    // This happens with pointers to member functions in C++.
-    if (CE->getOpcode() == Instruction::IntToPtr && NumIdx == 1 &&
-        isa<ConstantInt>(CE->getOperand(0)) && isa<ConstantInt>(Idxs[0]) &&
-        cast<PointerType>(CE->getType())->getElementType() ==
-            Type::getInt8Ty(Context)) {
-      Constant *Base = CE->getOperand(0);
-      Constant *Offset = Idxs[0];
-
-      // Convert the smaller integer to the larger type.
-      if (Offset->getType()->getPrimitiveSizeInBits() < 
-          Base->getType()->getPrimitiveSizeInBits())
-        Offset = ConstantExpr::getSExt(Offset, Base->getType());
-      else if (Base->getType()->getPrimitiveSizeInBits() <
-               Offset->getType()->getPrimitiveSizeInBits())
-        Base = ConstantExpr::getZExt(Base, Offset->getType());
-
-      Base = ConstantExpr::getAdd(Base, Offset);
-      return ConstantExpr::getIntToPtr(Base, CE->getType());
-    }
   }
 
   // Check to see if any array indices are not within the corresponding