[InstCombine] Simplify gep (gep p, a), (b-a)
Patch by Andrea Canciani.
Differential Revision: https://reviews.llvm.org/D27413
llvm-svn: 292506
diff --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index f6d1a1e..24517a8 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1559,27 +1559,21 @@
// Replace: gep (gep %P, long B), long A, ...
// With: T = long A+B; gep %P, T, ...
//
- Value *Sum;
Value *SO1 = Src->getOperand(Src->getNumOperands()-1);
Value *GO1 = GEP.getOperand(1);
- if (SO1 == Constant::getNullValue(SO1->getType())) {
- Sum = GO1;
- } else if (GO1 == Constant::getNullValue(GO1->getType())) {
- Sum = SO1;
- } else {
- // If they aren't the same type, then the input hasn't been processed
- // by the loop above yet (which canonicalizes sequential index types to
- // intptr_t). Just avoid transforming this until the input has been
- // normalized.
- if (SO1->getType() != GO1->getType())
- return nullptr;
- // Only do the combine when GO1 and SO1 are both constants. Only in
- // this case, we are sure the cost after the merge is never more than
- // that before the merge.
- if (!isa<Constant>(GO1) || !isa<Constant>(SO1))
- return nullptr;
- Sum = Builder->CreateAdd(SO1, GO1, PtrOp->getName()+".sum");
- }
+
+ // If they aren't the same type, then the input hasn't been processed
+ // by the loop above yet (which canonicalizes sequential index types to
+ // intptr_t). Just avoid transforming this until the input has been
+ // normalized.
+ if (SO1->getType() != GO1->getType())
+ return nullptr;
+
+ Value* Sum = SimplifyAddInst(GO1, SO1, false, false, DL, &TLI, &DT, &AC);
+ // Only do the combine when we are sure the cost after the
+ // merge is never more than that before the merge.
+ if (Sum == nullptr)
+ return nullptr;
// Update the GEP in place if possible.
if (Src->getNumOperands() == 2) {