From 462ab9810dd1774970e44264c35e8aec35e7460a Mon Sep 17 00:00:00 2001
From: Florian Hahn <flo@fhahn.com>
Date: Sun, 16 Oct 2022 23:24:06 +0100
Subject: [PATCH] [ConstraintElim] Fix signed integer overflow for inbounds
 GEP.

For inbounds GEPs, signed overflow yields poison, so it is fine for the
coefficients to wrap as well. This fixes an UBSan failure.
---
 llvm/lib/Transforms/Scalar/ConstraintElimination.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 1be2358..c208eb3 100644
--- a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
+++ b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
@@ -270,7 +270,7 @@ decomposeGEP(GetElementPtrInst &GEP,
       Result.emplace_back(Scale, Index);
     } else {
       for (auto &KV : IdxResult)
-        KV.Coefficient *= Scale;
+        KV.Coefficient = multiplyWithOverflow(KV.Coefficient, Scale);
       Result[0].Coefficient += IdxResult[0].Coefficient;
       append_range(Result, ArrayRef<DecompEntry>(IdxResult).drop_front());
     }
-- 
2.7.4