[MC] Use COMDAT for LSDA only if IR comdat type is any

[phosek]

Summary

This fixed issue introduced in 16af97393346ad636298605930a8b503a55eb40a
and 796feb61637c407aefcc0d462f24a1cc41f350d8.

[MaskRay]

Test?

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

897

IsComdat -> IsComdatAny

[phosek]

In D100909#2703521, @MaskRay wrote:

Test?

Added.

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

897

We use IsComdat elsewhere in this file so I'd prefer to keep them consistent.

[MaskRay]

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

897

But the name is now confusing. This now specifically refers to Comdat::Any. Readers could interpret IsComdat as any comdat kind.

llvm/test/CodeGen/X86/elf-group-gcc_except_table.ll

1 ↗

(On Diff #339113)

This can be placed into gcc_except_table-multi.ll

[phosek]

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

897

That name is referring to the name of the getELFSection argument which is called IsComdat, not to its value. I'm fine changing the name if you want, but I'd prefer doing it consistently across the entire file in a follow up change.

[MaskRay]

Thanks!

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

MCSection *TargetLoweringObjectFileELF::getSectionForLSDA(
   // Re-use this path if LSDASection is null as in the Arm EHABI.
   if (!LSDASection || (!F.hasComdat() && !TM.getFunctionSections()))
     return LSDASection;
 
   const auto *LSDA = cast<MCSectionELF>(LSDASection);
   unsigned Flags = LSDA->getFlags();
   const MCSymbolELF *LinkedToSym = nullptr;
   StringRef Group;
+  bool IsComdat = false;
   if (const Comdat *C = getELFComdat(&F)) {
     Flags |= ELF::SHF_GROUP;
     Group = C->getName();
+    IsComdat = C->getSelectionKind() == Comdat::Any;
   }
   // Use SHF_LINK_ORDER to facilitate --gc-sections if we can use GNU ld>=2.36
   // or LLD, which support mixed SHF_LINK_ORDER & non-SHF_LINK_ORDER.
   if (TM.getFunctionSections() &&
       (getContext().getAsmInfo()->useIntegratedAssembler() &&
        getContext().getAsmInfo()->binutilsIsAtLeast(2, 36))) {
     Flags |= ELF::SHF_LINK_ORDER;
     LinkedToSym = cast<MCSymbolELF>(&FnSym);
   }
 
   // Append the function name as the suffix like GCC, assuming
   // -funique-section-names applies to .gcc_except_table sections.
   return getContext().getELFSection(
       (TM.getUniqueSectionNames() ? LSDA->getName() + "." + F.getName()
                                   : LSDA->getName()),
-      LSDA->getType(), Flags, 0, Group, F.hasComdat(), MCSection::NonUniqueID,
+      LSDA->getType(), Flags, 0, Group, IsComdat, MCSection::NonUniqueID,
       LinkedToSym);
 }
 
 bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
     bool UsesLabelDifference, const Function &F) const {
   // We can always create relative relocations, so use another section
   // that can be marked non-executable.
   return false;

llvm/test/CodeGen/X86/gcc_except_table-multi.ll

lpad:
   %0 = landingpad { i8*, i32 } catch i8* bitcast (i8** @_ZTIi to i8*)
   br label %eh.resume
 try.cont:
   ret i32 0
 eh.resume:
   resume { i8*, i32 } %0
 }
 
+;; If the function is in a comdat group with noduplicates kind, the generated
+;; .gcc_except_table should is lowered to a zero-flag ELF section group.
+$zero = comdat noduplicates
+define i32 @zero() uwtable comdat personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*) {
+; CHECK-LABEL:       zero:
+; CHECK:             .cfi_endproc
+; NORMAL-NEXT:       .section .gcc_except_table.zero,"aG",@progbits,zero{{$}}
+; SEP_BFD-NEXT:      .section .gcc_except_table.zero,"aG",@progbits,zero{{$}}
+; SEP-NEXT:          .section .gcc_except_table.zero,"aGo",@progbits,zero,zero{{$}}
+; SEP_NOUNIQUE-NEXT: .section .gcc_except_table,"aG",@progbits,zero{{$}}
+; NOUNIQUE-NEXT:     .section .gcc_except_table,"aG",@progbits,zero{{$}}
+entry:
+  invoke void @ext() to label %try.cont unwind label %lpad
+lpad:
+  %0 = landingpad { i8*, i32 } catch i8* bitcast (i8** @_ZTIi to i8*)
+  br label %eh.resume
+try.cont:
+  ret i32 0
+eh.resume:
+  resume { i8*, i32 } %0
+}
+
 declare void @ext()
 
 declare i32 @__gxx_personality_v0(...)