[llvm] r239629 - Refix a use of explicit pointer types in GEP constant folding

[David Blaikie]

Author: dblaikie
Date: Fri Jun 12 13:22:03 2015
New Revision: 239629

URL: http://llvm.org/viewvc/llvm-project?rev=239629&view=rev
Log:
Refix a use of explicit pointer types in GEP constant folding

In the glorious future of opaque pointer types, it won't be possible to
retrieve the pointee type of a pointer type which is what's being done
in this GEP loop - but the first iteration is always a pointer type and
the loop doesn't care about that case, except whether or not the index
is a constant.

So pull that special case out before the loop and start at the second
iteration (index 1) instead.

Originally committed in r236670 and reverted with a test case in
r239015. This change keeps the test case working while also avoiding
depending on pointee types.

Modified:
    llvm/trunk/lib/IR/ConstantFold.cpp

Modified: llvm/trunk/lib/IR/ConstantFold.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/IR/ConstantFold.cpp?rev=239629&r1=239628&r2=239629&view=diff
==============================================================================
--- llvm/trunk/lib/IR/ConstantFold.cpp (original)
+++ llvm/trunk/lib/IR/ConstantFold.cpp Fri Jun 12 13:22:03 2015
@@ -2163,11 +2163,11 @@ static Constant *ConstantFoldGetElementP
   // Check to see if any array indices are not within the corresponding
   // notional array or vector bounds. If so, try to determine if they can be
   // factored out into preceding dimensions.
-  bool Unknown = false;
   SmallVector<Constant *, 8> NewIdxs;
-  Type *Ty = C->getType();
-  Type *Prev = nullptr;
-  for (unsigned i = 0, e = Idxs.size(); i != e;
+  Type *Ty = PointeeTy;
+  Type *Prev = C->getType();
+  bool Unknown = !isa<ConstantInt>(Idxs[0]);
+  for (unsigned i = 1, e = Idxs.size(); i != e;
        Prev = Ty, Ty = cast<CompositeType>(Ty)->getTypeAtIndex(Idxs[i]), ++i) {
     if (ConstantInt *CI = dyn_cast<ConstantInt>(Idxs[i])) {
       if (isa<ArrayType>(Ty) || isa<VectorType>(Ty))