[llvm] 462ab98 - [ConstraintElim] Fix signed integer overflow for inbounds GEP.

[Florian Hahn via llvm-commits]

Author: Florian Hahn
Date: 2022-10-16T23:25:28+01:00
New Revision: 462ab9810dd1774970e44264c35e8aec35e7460a

URL: https://github.com/llvm/llvm-project/commit/462ab9810dd1774970e44264c35e8aec35e7460a
DIFF: https://github.com/llvm/llvm-project/commit/462ab9810dd1774970e44264c35e8aec35e7460a.diff

LOG: [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.

Added: 
    

Modified: 
    llvm/lib/Transforms/Scalar/ConstraintElimination.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp b/llvm/lib/Transforms/Scalar/ConstraintElimination.cpp
index 1be235898be7..c208eb36449c 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());
     }