[llvm] 714c4a5 - [InstCombine] Ignore frees when inferring inbounds (#202304)

[via llvm-commits]

Author: Nikita Popov
Date: 2026-06-08T14:36:06+02:00
New Revision: 714c4a5f8007e5ee52a6338f325680fb7ab89a7a

URL: https://github.com/llvm/llvm-project/commit/714c4a5f8007e5ee52a6338f325680fb7ab89a7a
DIFF: https://github.com/llvm/llvm-project/commit/714c4a5f8007e5ee52a6338f325680fb7ab89a7a.diff

LOG: [InstCombine] Ignore frees when inferring inbounds (#202304)

>From LangRef:

> Note that the object does not have to be live anymore; being
> in-bounds of a deallocated object is sufficient.

Added: 
    

Modified: 
    llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
    llvm/test/Transforms/InstCombine/inbounds-gep.ll

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
index 89bf4bf713421..608966a5e9289 100644
--- a/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -3615,7 +3615,9 @@ Instruction *InstCombinerImpl::visitGetElementPtrInst(GetElementPtrInst &GEP) {
     bool CanBeNull, CanBeFreed;
     uint64_t DerefBytes = UnderlyingPtrOp->getPointerDereferenceableBytes(
         DL, CanBeNull, CanBeFreed);
-    if (!CanBeNull && !CanBeFreed && DerefBytes != 0) {
+    // We can ignore CanBeFreed here, because inbounds is explicitly allowed to
+    // refer to a deallocated object.
+    if (!CanBeNull && DerefBytes != 0) {
       if (GEP.accumulateConstantOffset(DL, BasePtrOffset) &&
           BasePtrOffset.isNonNegative()) {
         APInt AllocSize(IdxWidth, DerefBytes);

diff  --git a/llvm/test/Transforms/InstCombine/inbounds-gep.ll b/llvm/test/Transforms/InstCombine/inbounds-gep.ll
index 467e5a82f89cc..0ea71da485766 100644
--- a/llvm/test/Transforms/InstCombine/inbounds-gep.ll
+++ b/llvm/test/Transforms/InstCombine/inbounds-gep.ll
@@ -1,5 +1,6 @@
 ; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
 ; RUN: opt -passes=instcombine -S < %s | FileCheck %s
+; RUN: opt -passes=instcombine -use-dereferenceable-at-point-semantics -S < %s | FileCheck %s
 
 declare ptr @g()
 declare ptr @use(ptr)