From: David Blaikie <dblaikie@gmail.com>
Date: Fri, 12 Jun 2015 18:22:03 +0000 (+0000)
Subject: Refix a use of explicit pointer types in GEP constant folding
X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=commitdiff_plain;h=d25af8c3964a96b8bb85fbfc51147b411d344e52

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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@239629 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/IR/ConstantFold.cpp b/lib/IR/ConstantFold.cpp
index 2efc61242ea..46bb20e0d1b 100644
--- a/lib/IR/ConstantFold.cpp
+++ b/lib/IR/ConstantFold.cpp
@@ -2163,11 +2163,11 @@ static Constant *ConstantFoldGetElementPtrImpl(Type *PointeeTy, Constant *C,
   // 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))