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From ce610275edfd05704d5058716a971c2003299b95 Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Wed, 30 Jul 2025 17:52:08 +0200
Subject: [PATCH 1/2] [InstCombine] Don't handle non-canonical index type in
icmp of load fold (#151346)
We should just bail out and wait for it to be canonicalized. The current
implementation could emit a trunc without actually performing the
transform.
---
.../InstCombine/InstCombineCompares.cpp | 16 +++++-----------
1 file changed, 5 insertions(+), 11 deletions(-)
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
index 810ce7d382ae..19dd71355622 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -161,6 +161,11 @@ Instruction *InstCombinerImpl::foldCmpLoadFromIndexedGlobal(
LaterIndices.push_back(IdxVal);
}
+ Value *Idx = GEP->getOperand(2);
+ // If the index type is non-canonical, wait for it to be canonicalized.
+ if (Idx->getType() != DL.getIndexType(GEP->getType()))
+ return nullptr;
+
enum { Overdefined = -3, Undefined = -2 };
// Variables for our state machines.
@@ -288,17 +293,6 @@ Instruction *InstCombinerImpl::foldCmpLoadFromIndexedGlobal(
// Now that we've scanned the entire array, emit our new comparison(s). We
// order the state machines in complexity of the generated code.
- Value *Idx = GEP->getOperand(2);
-
- // If the index is larger than the pointer offset size of the target, truncate
- // the index down like the GEP would do implicitly. We don't have to do this
- // for an inbounds GEP because the index can't be out of range.
- if (!GEP->isInBounds()) {
- Type *PtrIdxTy = DL.getIndexType(GEP->getType());
- unsigned OffsetSize = PtrIdxTy->getIntegerBitWidth();
- if (Idx->getType()->getPrimitiveSizeInBits().getFixedValue() > OffsetSize)
- Idx = Builder.CreateTrunc(Idx, PtrIdxTy);
- }
// If inbounds keyword is not present, Idx * ElementSize can overflow.
// Let's assume that ElementSize is 2 and the wanted value is at offset 0.
--
2.51.0