[AArch64] Restrict .variant_pcs directive to ELF targets

[c-rhodes]

Directive was implemented in c87bd2d to support lazy binding and is emitted for vector PCS functions. It's specific to ELF but is currently emitted for all binary formats and crashing on non-ELF targets.

Fixes #138260

[llvmbot]

@llvm/pr-subscribers-backend-aarch64

Author: Cullen Rhodes (c-rhodes)

Changes

Directive was implemented in c87bd2d to support lazy binding and is emitted for vector PCS functions. It's specific to ELF but is currently emitted for all binary formats and crashing on non-ELF targets.

Fixes #138260

[1] https://github.com/ARM-software/abi-aa/blob/master/aaelf64/aaelf64.rst#st-other-values

---

Full diff: https://github.com/llvm/llvm-project/pull/140022.diff

2 Files Affected:

• (modified) llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp (+7-6)
• (modified) llvm/test/CodeGen/AArch64/variant-pcs.ll (+7)

diff --git a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
index a53606851d0a2..f55b7ef7c20bb 100644
--- a/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
+++ b/llvm/lib/Target/AArch64/AArch64AsmPrinter.cpp
@@ -1344,10 +1344,12 @@ AArch64AsmPrinter::getCodeViewJumpTableInfo(int JTI,
 }
 
 void AArch64AsmPrinter::emitFunctionEntryLabel() {
-  if (MF->getFunction().getCallingConv() == CallingConv::AArch64_VectorCall ||
-      MF->getFunction().getCallingConv() ==
-          CallingConv::AArch64_SVE_VectorCall ||
-      MF->getInfo<AArch64FunctionInfo>()->isSVECC()) {
+  const Triple &TT = TM.getTargetTriple();
+  if (TT.isOSBinFormatELF() &&
+      (MF->getFunction().getCallingConv() == CallingConv::AArch64_VectorCall ||
+       MF->getFunction().getCallingConv() ==
+           CallingConv::AArch64_SVE_VectorCall ||
+       MF->getInfo<AArch64FunctionInfo>()->isSVECC())) {
     auto *TS =
         static_cast<AArch64TargetStreamer *>(OutStreamer->getTargetStreamer());
     TS->emitDirectiveVariantPCS(CurrentFnSym);
@@ -1355,8 +1357,7 @@ void AArch64AsmPrinter::emitFunctionEntryLabel() {
 
   AsmPrinter::emitFunctionEntryLabel();
 
-  if (TM.getTargetTriple().isWindowsArm64EC() &&
-      !MF->getFunction().hasLocalLinkage()) {
+  if (TT.isWindowsArm64EC() && !MF->getFunction().hasLocalLinkage()) {
     // For ARM64EC targets, a function definition's name is mangled differently
     // from the normal symbol, emit required aliases here.
     auto emitFunctionAlias = [&](MCSymbol *Src, MCSymbol *Dst) {
diff --git a/llvm/test/CodeGen/AArch64/variant-pcs.ll b/llvm/test/CodeGen/AArch64/variant-pcs.ll
index 49c504177358e..38510751fdd43 100644
--- a/llvm/test/CodeGen/AArch64/variant-pcs.ll
+++ b/llvm/test/CodeGen/AArch64/variant-pcs.ll
@@ -1,6 +1,13 @@
 ; RUN: llc -mtriple=aarch64-linux-gnu -mattr=+sve -o - %s | FileCheck %s --check-prefix=CHECK-ASM --strict-whitespace
+; RUN: llc -mtriple=arm64-apple-macosx -mattr=+sve -o - %s | FileCheck %s --check-prefix=CHECK-ASM-NON-ELF-TARGET
 ; RUN: llc -mtriple=aarch64-linux-gnu -mattr=+sve -filetype=obj -o - %s \
 ; RUN:   | llvm-readobj --symbols - | FileCheck %s --check-prefix=CHECK-OBJ
+; RUN: llc -mtriple=arm64-apple-macosx -mattr=+sve -filetype=obj -o - %s \
+; RUN:   | llvm-readobj --symbols - | FileCheck %s --check-prefix=CHECK-OBJ-NON-ELF-TARGET
+
+; .variant_pcs directive should only be emitted for ELF targets.
+; CHECK-ASM-NON-ELF-TARGET-NOT: .variant_pcs
+; CHECK-OBJ-NON-ELF-TARGET-NOT: Other [ (0x80)
 
 define i32 @base_pcs() {
 ; CHECK-ASM-LABEL: base_pcs:

[davemgreen]

Is this similar to #138924? @MacDue

[c-rhodes]

Is this similar to #138924? @MacDue

seems so! Apologies I wasn't aware there was a fix in progress already.. I came across this via #138260 the other day and there's no link to the existing PR, perhaps @MacDue wasn't aware there's an existing issue.

[sdesmalen-arm]

This indeed seems a duplicate of #138924. Since this version addresses already the comment I left on the other PR, I'm happy to accept it if you address my nit on the test. Thanks!

[sdesmalen-arm]

I don't think this check makes sense, because this seems ELF specific. You can just remove the | FileCheck %s --check-prefix=CHECK-OBJ-NON-ELF-TARGET part of the RUN line, we just need to make sure it doesn't fail to compile.

[c-rhodes]

This indeed seems a duplicate of #138924. Since this version addresses already the comment I left on the other PR, I'm happy to accept it if you address my nit on the test. Thanks!

Appreciate it, but Ben got there first so he can have this one.

[MacDue]

This indeed seems a duplicate of #138924. Since this version addresses already the comment I left on the other PR, I'm happy to accept it if you address my nit on the test. Thanks!

Appreciate it, but Ben got there first so he can have this one.

I think this version of the fix is more correct than mine, so I'll take version this and add you as a co-author on my PR 👍

[MacDue]

I've pushed your patch to #138924 (and addressed @sdesmalen-arm's nit).