[PowerPC][AIX] Emit weak_definition symbols as weak externals

[aabhinavg1]

• On AIX, the assembler does not recognize '.weak_definition'.
• Emit MCSA_WeakDefinition symbols using the standard weak directive (.weak) and set storage class to C_WEAKEXT in XCOFF.
• Added test llvm/test/MC/PowerPC/aix-weak-definition.s
  Fixes powerpc64-ibm-aix: the .weak assembler directive is not supported #130269

Fixes #130269

Testing:

• command

ninja check-llvm-codegen-powerpc

===== Before Patch ===== [779/780] Running lit suite /llvm/test/CodeGen/PowerPC Testing Time: 44.38s Total Discovered Tests: 1952 Unsupported : 38 (1.95%) Passed : 1907 (97.69%) Expectedly Failed: 7 (0.36%)

===== After Patch ===== [779/780] Running lit suite /llvm/test/CodeGen/PowerPC Testing Time: 120.31s Total Discovered Tests: 1952 Unsupported : 3 (0.15%) Passed : 1941 (99.44%) Expectedly Failed: 8 (0.41%)

Verification:

$ ../bin/clang -target powerpc64-ibm-aix -S test.c -o test.s $ cat test.s .file "test.c",,"LLVM version 22.0.0git ..."  .csect ..text..[PR],5  .rename ..text..[PR],"" # Start of file scope inline assembly .weak foo foo: blr # End of file scope inline assembly .machine "PWR7"

Input C code:

__asm__(".weak_definition foo\n" "foo:\n" "blr");

Outcome:

• .weak_definition in the source is correctly mapped to .weak in the assembly on AIX.
• Confirms the patch fixes the AIX assembler issue without affecting other targets.

[llvmbot]

@llvm/pr-subscribers-backend-powerpc

Author: None (aabhinavg1)

Changes

• On AIX, the assembler does not recognize '.weak_definition'.
• Emit MCSA_WeakDefinition symbols using the standard weak directive (.weak) and set storage class to C_WEAKEXT in XCOFF.
• Added test llvm/test/MC/PowerPC/aix-weak-definition.s
  Fixes #130269

Fixes #130269

Testing:

• command

ninja check-llvm-codegen-powerpc

===== Before Patch ===== [779/780] Running lit suite /llvm/test/CodeGen/PowerPC Testing Time: 44.38s Total Discovered Tests: 1952 Unsupported : 38 (1.95%) Passed : 1907 (97.69%) Expectedly Failed: 7 (0.36%)

===== After Patch ===== [779/780] Running lit suite /llvm/test/CodeGen/PowerPC Testing Time: 120.31s Total Discovered Tests: 1952 Unsupported : 3 (0.15%) Passed : 1941 (99.44%) Expectedly Failed: 8 (0.41%)

Verification:

$ ../bin/clang -target powerpc64-ibm-aix -S test.c -o test.s $ cat test.s .file "test.c",,"LLVM version 22.0.0git ..."  .csect ..text..[PR],5  .rename ..text..[PR],"" # Start of file scope inline assembly .weak foo foo: blr # End of file scope inline assembly .machine "PWR7"

Input C code:

__asm__(".weak_definition foo\n" "foo:\n" "blr");

Outcome:

• .weak_definition in the source is correctly mapped to .weak in the assembly on AIX.
• Confirms the patch fixes the AIX assembler issue without affecting other targets.

---

Full diff: https://github.com/llvm/llvm-project/pull/156072.diff

3 Files Affected:

• (modified) llvm/lib/MC/MCAsmStreamer.cpp (+11-3)
• (modified) llvm/lib/MC/MCXCOFFStreamer.cpp (+7)
• (added) llvm/test/MC/PowerPC/aix-weak-definition.s (+13)

diff --git a/llvm/lib/MC/MCAsmStreamer.cpp b/llvm/lib/MC/MCAsmStreamer.cpp index be8c022f39ad1..7b1a1878915bc 100644 --- a/llvm/lib/MC/MCAsmStreamer.cpp +++ b/llvm/lib/MC/MCAsmStreamer.cpp @@ -764,10 +764,18 @@ bool MCAsmStreamer::emitSymbolAttribute(MCSymbol *Symbol, OS << "\t.extern\t"; break; case MCSA_Weak: OS << MAI->getWeakDirective(); break; - case MCSA_WeakDefinition: - OS << "\t.weak_definition\t"; + case MCSA_WeakDefinition: { + // AIX, use the standard weak directive (.weak) instead of + //'.weak_definition' because the AIX assembler does not + // recognize the '.weak_definition' directive. + const llvm::Triple &TT = getContext().getTargetTriple(); + if (TT.isOSAIX()) + OS << MAI->getWeakDirective(); + else + OS << "\t.weak_definition\t"; break; - // .weak_reference + } + // .weak_reference case MCSA_WeakReference: OS << MAI->getWeakRefDirective(); break; case MCSA_WeakDefAutoPrivate: OS << "\t.weak_def_can_be_hidden\t"; break; case MCSA_Cold: diff --git a/llvm/lib/MC/MCXCOFFStreamer.cpp b/llvm/lib/MC/MCXCOFFStreamer.cpp index 4bf14c11068cb..cd5398dc7bc3b 100644 --- a/llvm/lib/MC/MCXCOFFStreamer.cpp +++ b/llvm/lib/MC/MCXCOFFStreamer.cpp @@ -72,6 +72,13 @@ bool MCXCOFFStreamer::emitSymbolAttribute(MCSymbol *Sym, Symbol->setStorageClass(XCOFF::C_WEAKEXT); Symbol->setExternal(true); break; + case llvm::MCSA_WeakDefinition: + // On AIX/XCOFF, a weak definition symbol should be emitted + // as an external weak symbol (C_WEAKEXT), since the assembler + // does not support '.weak_definition' directly. + Symbol->setStorageClass(XCOFF::C_WEAKEXT); + Symbol->setExternal(true); + break; case llvm::MCSA_Hidden: Symbol->setVisibilityType(XCOFF::SYM_V_HIDDEN); break; diff --git a/llvm/test/MC/PowerPC/aix-weak-definition.s b/llvm/test/MC/PowerPC/aix-weak-definition.s new file mode 100644 index 0000000000000..6bab51b91c63d --- /dev/null +++ b/llvm/test/MC/PowerPC/aix-weak-definition.s @@ -0,0 +1,13 @@ +## Check that weak_definition symbols are emitted as weak externals. +# Note: On AIX, .weak_definition is mapped to .weak by LLVM's backend. +# RUN: llvm-mc -triple powerpc-ibm-aix-xcoff %s -filetype=obj -o - | \ +# RUN: llvm-objdump --syms - | FileCheck %s + + .weak_definition foo # LLVM IR WeakDefinition → .weak on AIX +foo: + blr + +# CHECK: SYMBOL TABLE: +# CHECK-NEXT: 00000000 df *DEBUG* 00000000 .file +# CHECK-NEXT: 00000000 l .text 00000004 +# CHECK-NEXT: 00000000 w F .text (csect: ) 00000000 foo 

[tonykuttai]

Adding @hubert-reinterpretcast & @daltenty.

[MaskRay]

Do you need .weak_definition? ELF doesn't support .weak_definition and we don't use MCSA_WeakDefinition for ELF. You can use MCSA_Weak for XCOFF