[llvm] e8b7181 - [Evaluator] require invariant size to fully span the global (#179518)

[via llvm-commits]

Author: Jameson Nash
Date: 2026-02-04T13:08:06-05:00
New Revision: e8b7181762826371324b5c05e3e84d1b685fcf4c

URL: https://github.com/llvm/llvm-project/commit/e8b7181762826371324b5c05e3e84d1b685fcf4c
DIFF: https://github.com/llvm/llvm-project/commit/e8b7181762826371324b5c05e3e84d1b685fcf4c.diff

LOG: [Evaluator] require invariant size to fully span the global (#179518)

Relying on the semantics of the type here is a bit potentially awkward,
since the full allocated space may be accessible to the user if desired,
since that space is defined to be a part of the type's sizeof
computation (e.g. for a `memcpy(gv, gv, sizeof(*gv))` or when making an
array of them). It also gets in the way of removing getAllocatedType
from AllocaInst entirely (they are converted to GlobalVariable
sometimes). It was originally added in
519561f418c77dcf46fd6d96d25d884fa07fd7da, though "correct size" is a
difficult thing to define.

The frontend (in clang) appears to always emit the full type size here,
so there seems like this shouldn't be visible change to clang users.

This is still a bit awkward though, since a global is defined to be any
size that is bigger than this unless it has a known initizalizer,
rendering the test still incomplete here against the IR semantics.

Added: 
    

Modified: 
    llvm/lib/Transforms/Utils/Evaluator.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Utils/Evaluator.cpp b/llvm/lib/Transforms/Utils/Evaluator.cpp
index 3a5c7a3b1738e..b2ee1da143ba7 100644
--- a/llvm/lib/Transforms/Utils/Evaluator.cpp
+++ b/llvm/lib/Transforms/Utils/Evaluator.cpp
@@ -431,10 +431,9 @@ bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB,
           Value *PtrArg = getVal(II->getArgOperand(1));
           Value *Ptr = PtrArg->stripPointerCasts();
           if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
-            Type *ElemTy = GV->getValueType();
+            uint64_t MinGVSize = GV->getGlobalSize(DL);
             if (!Size->isMinusOne() &&
-                Size->getValue().getLimitedValue() >=
-                    DL.getTypeStoreSize(ElemTy)) {
+                Size->getValue().getLimitedValue() >= MinGVSize) {
               Invariants.insert(GV);
               LLVM_DEBUG(dbgs() << "Found a global var that is an invariant: "
                                 << *GV << "\n");