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[llvm][CFI] Do not canonicalize COFF functions in a comdat #139962

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Merged
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May 16, 2025
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[llvm][CFI] Do not canonicalize COFF functions in a comdat #139962

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16 changes: 15 additions & 1 deletion llvm/lib/Transforms/IPO/LowerTypeTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1715,8 +1715,22 @@ void LowerTypeTestsModule::buildBitSetsFromFunctionsNative(
F->getValueType(), 0, F->getLinkage(), "", CombinedGlobalElemPtr, &M);
FAlias->setVisibility(F->getVisibility());
FAlias->takeName(F);
if (FAlias->hasName())
if (FAlias->hasName()) {
F->setName(FAlias->getName() + ".cfi");
// For COFF we should also rename the comdat if this function also
// happens to be the key function. Even if the comdat name changes, this
// should still be fine since comdat and symbol resolution happens
// before LTO, so all symbols which would prevail have been selected.
if (F->hasComdat() && ObjectFormat == Triple::COFF &&
F->getComdat()->getName() == FAlias->getName()) {
Comdat *OldComdat = F->getComdat();
Comdat *NewComdat = M.getOrInsertComdat(F->getName());
for (GlobalObject &GO : M.global_objects()) {
if (GO.getComdat() == OldComdat)
GO.setComdat(NewComdat);
}
}
}
replaceCfiUses(F, FAlias, IsJumpTableCanonical);
if (!F->hasLocalLinkage())
F->setVisibility(GlobalVariable::HiddenVisibility);
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35 changes: 35 additions & 0 deletions llvm/test/Transforms/LowerTypeTests/cfi-coff-comdat-rename.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,35 @@
; RUN: opt -S -passes=lowertypetests %s | FileCheck %s

;; This is a check to assert we don't crash with:
;;
;; LLVM ERROR: Associative COMDAT symbol '...' does not exist.
;;
;; So this just needs to exit normally.
; RUN: opt -S -passes=lowertypetests %s | llc -asm-verbose=false

target datalayout = "e-p:64:64"
target triple = "x86_64-pc-windows-msvc"

@a = global [2 x ptr] [ptr @f1, ptr @f2]

; CHECK: $f1.cfi = comdat any
$f1 = comdat any

; CHECK: @f1.cfi() comdat !type !0
define void @f1() comdat !type !0 {
ret void
}

; CHECK: @f2.cfi() comdat($f1.cfi) !type !0
define void @f2() comdat($f1) !type !0 {
ret void
}

declare i1 @llvm.type.test(ptr %ptr, metadata %bitset) nounwind readnone

define i1 @foo(ptr %p) {
%x = call i1 @llvm.type.test(ptr %p, metadata !"typeid1")
ret i1 %x
}

!0 = !{i32 0, !"typeid1"}