[win][arm64ec] Handle available_externally functions
#151610
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@llvm/pr-subscribers-backend-aarch64 @llvm/pr-subscribers-platform-windows Author: Daniel Paoliello (dpaoliello) ChangesWhile testing Arm64EC, I observed that LLVM crashes when an This the fix from #151409 plus a dedicated test. Full diff: https://github.com/llvm/llvm-project/pull/151610.diff 2 Files Affected:
diff --git a/llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp b/llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp
index 509cbb092705d..8390c1f291365 100644
--- a/llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp
+++ b/llvm/lib/Target/AArch64/AArch64Arm64ECCallLowering.cpp
@@ -872,7 +872,7 @@ bool AArch64Arm64ECCallLowering::runOnModule(Module &Mod) {
if (!F.isDeclaration() && (!F.hasLocalLinkage() || F.hasAddressTaken()) &&
F.getCallingConv() != CallingConv::ARM64EC_Thunk_Native &&
F.getCallingConv() != CallingConv::ARM64EC_Thunk_X64) {
- if (!F.hasComdat())
+ if (!F.hasComdat() && !F.isDeclarationForLinker())
F.setComdat(Mod.getOrInsertComdat(F.getName()));
ThunkMapping.push_back(
{&F, buildEntryThunk(&F), Arm64ECThunkType::Entry});
diff --git a/llvm/test/CodeGen/AArch64/arm64ec-available-externally.ll b/llvm/test/CodeGen/AArch64/arm64ec-available-externally.ll
new file mode 100644
index 0000000000000..9457302403d4c
--- /dev/null
+++ b/llvm/test/CodeGen/AArch64/arm64ec-available-externally.ll
@@ -0,0 +1,9 @@
+; RUN: llc -mtriple arm64ec-windows-msvc < %s
+
+; Arm64EC Regression Test: The Arm64EC Call Lowering was placing "available
+; externally" items in COMDATs, which is not permitted by the module verifier.
+
+define available_externally i32 @f() {
+entry:
+ ret i32 0
+}
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| @@ -872,7 +872,7 @@ bool AArch64Arm64ECCallLowering::runOnModule(Module &Mod) { | |||
| if (!F.isDeclaration() && (!F.hasLocalLinkage() || F.hasAddressTaken()) && | |||
| F.getCallingConv() != CallingConv::ARM64EC_Thunk_Native && | |||
| F.getCallingConv() != CallingConv::ARM64EC_Thunk_X64) { | |||
| if (!F.hasComdat()) | |||
| if (!F.hasComdat() && !F.isDeclarationForLinker()) | |||
| F.setComdat(Mod.getOrInsertComdat(F.getName())); | |||
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We also want to skip creating an entry thunk for an available_externally function. The thunk should be provided by the translation unit that actually defines the function, and emitting an extra one could cause weird linker behavior.
We still may need a exit thunk, if the function is called.
I'd like to see the test show that we don't create an entry thunk, and do create an exit thunk.
There was a problem hiding this comment.
Good call: expanded the test and fixed other cases where we should be using isDeclarationForLinker instead of isDeclaration.
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LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/11/builds/20918 Here is the relevant piece of the build log for the reference |
Seems unrelated: this change was to Arm64EC call lowering, which is not run at all for x86. Additionally, the crash is happening at link time (with non-LTO objects), not compilation time. |
krishna2803
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Aug 12, 2025
While testing Arm64EC, I observed that LLVM crashes when an `available_externally` function is used as it tries to place it in a COMDAT, which is not permitted by the verifier. This the fix from llvm#151409 plus a dedicated test.
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While testing Arm64EC, I observed that LLVM crashes when an
available_externallyfunction is used as it tries to place it in a COMDAT, which is not permitted by the verifier.This the fix from #151409 plus a dedicated test.