[MergeICmps] Do not perform the transformation if GEP is used outside of block
Summary:
This patch prevents MergeICmps to performn the transformation if the address operand GEP of the load instruction has a use outside of the load's parent block. Without this patch, compiler crashes with the given test case because the use of `%first.i` is still around when the basic block is erased from https://github.com/llvm-mirror/llvm/blob/master/lib/Transforms/Scalar/MergeICmps.cpp#L620. I think checking `isUsedOutsideOfBlock` with `GEP` is the original intention of the code, as the checking for `LoadI` is already performed in the same function.
This patch is incomplete though, as this makes the pass overly conservative and fails the test `tuple-four-int8.ll`. I believe what needs to be done is checking if GEP has a use outside of block that is not the part of "Comparisons" chain. Submit the patch as of now to prevent compiler crash.
Reviewers: courbet, trentxintong
Reviewed By: courbet
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D54089
llvm-svn: 346151
diff --git a/llvm/lib/Transforms/Scalar/MergeICmps.cpp b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
index 3633485..69fd8b1 100644
--- a/llvm/lib/Transforms/Scalar/MergeICmps.cpp
+++ b/llvm/lib/Transforms/Scalar/MergeICmps.cpp
@@ -98,7 +98,7 @@
Value *const Addr = LoadI->getOperand(0);
if (auto *const GEP = dyn_cast<GetElementPtrInst>(Addr)) {
LLVM_DEBUG(dbgs() << "GEP\n");
- if (LoadI->isUsedOutsideOfBlock(LoadI->getParent())) {
+ if (GEP->isUsedOutsideOfBlock(LoadI->getParent())) {
LLVM_DEBUG(dbgs() << "used outside of block\n");
return {};
}