Implement a small optimization to handling of GEP's that are equivalent to casts.
This results in substantially reduced collapsing for some testcases
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@10002 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/DataStructure/Local.cpp b/lib/Analysis/DataStructure/Local.cpp
index 79f3920..a7cf854 100644
--- a/lib/Analysis/DataStructure/Local.cpp
+++ b/lib/Analysis/DataStructure/Local.cpp
@@ -308,6 +308,24 @@
DSNodeHandle Value = getValueDest(*GEP.getOperand(0));
if (Value.getNode() == 0) return;
+ // As a special case, if all of the index operands of GEP are constant zeros,
+ // handle this just like we handle casts (ie, don't do much).
+ bool AllZeros = true;
+ for (unsigned i = 1, e = GEP.getNumOperands(); i != e; ++i)
+ if (GEP.getOperand(i) !=
+ Constant::getNullValue(GEP.getOperand(i)->getType())) {
+ AllZeros = false;
+ break;
+ }
+
+ // If all of the indices are zero, the result points to the operand without
+ // applying the type.
+ if (AllZeros) {
+ setDestTo(GEP, Value);
+ return;
+ }
+
+
const PointerType *PTy = cast<PointerType>(GEP.getOperand(0)->getType());
const Type *CurTy = PTy->getElementType();