[MC] Default MCContext::UseNamesOnTempLabels to false and only set it to true for MCAsmStreamer

[MaskRay]

Summary

Only MCAsmStreamer (assembly output) needs to keep .Ltmp* names.

Similar to rL236642. Made the optimization available for cc1as as well.

This eliminates a behavior difference between llvm-mc -filetype=obj and cc1as, which caused
https://reviews.llvm.org/D74006#1890487

[efriedma]

Does UseNamesOnTempLabels really need to be configurable? If we're going to force it to false everywhere, might as well just get rid of it.

[efriedma]

In terms of tests, we can add cc1as tests to clang/test/Misc; just need to be marked REQUIRES: arm-registered-target or something like that.

That said, if we need to write cc1as-specific tests for anything other than the command-line parsing, probably something has gone wrong.

[MaskRay]

In D75097#1892545, @efriedma wrote:

In terms of tests, we can add cc1as tests to clang/test/Misc; just need to be marked REQUIRES: arm-registered-target or something like that.

That said, if we need to write cc1as-specific tests for anything other than the command-line parsing, probably something has gone wrong.

Thanks.

In D75097#1892543, @efriedma wrote:

Does UseNamesOnTempLabels really need to be configurable? If we're going to force it to false everywhere, might as well just get rid of it.

It is used by MCAsmStreamer (e.g. llvm-mc -filetype=asm; the output is also assembly).

[MaskRay]

Repurpose

[efriedma]

LGTM

[MaskRay]

Fix title

llvm/include/llvm/MC/MCContext.h

private:
 
     /// The maximum version of dwarf that we should emit.
     uint16_t DwarfVersion = 4;
 
     /// Honor temporary labels, this is useful for debugging semantic
     /// differences between temporary and non-temporary labels (primarily on
     /// Darwin).
     bool AllowTemporaryLabels = true;
-    bool UseNamesOnTempLabels = true;
+    bool UseNamesOnTempLabels = false;
 
     /// The Compile Unit ID that we are currently processing.
     unsigned DwarfCompileUnitID = 0;
 
     // Sections are differentiated by the quadruple (section_name, group_name,
     // unique_id, link_to_symbol_name). Sections sharing the same quadruple are
     // combined into one section.
     struct ELFSectionKey {

llvm/lib/CodeGen/LLVMTargetMachine.cpp

case CGFT_ObjectFile: {
     // Create the code emitter for the target if it exists.  If not, .o file
     // emission fails.
     MCCodeEmitter *MCE = getTarget().createMCCodeEmitter(MII, MRI, Context);
     MCAsmBackend *MAB =
         getTarget().createMCAsmBackend(STI, MRI, Options.MCOptions);
     if (!MCE || !MAB)
       return true;
 
-    // Don't waste memory on names of temp labels.
-    Context.setUseNamesOnTempLabels(false);
-
     Triple T(getTargetTriple().str());
     AsmStreamer.reset(getTarget().createMCObjectStreamer(
         T, Context, std::unique_ptr<MCAsmBackend>(MAB),
         DwoOut ? MAB->createDwoObjectWriter(Out, *DwoOut)
                : MAB->createObjectWriter(Out),
         std::unique_ptr<MCCodeEmitter>(MCE), STI, Options.MCOptions.MCRelaxAll,
         Options.MCOptions.MCIncrementalLinkerCompatible,
         /*DWARFMustBeAtTheEnd*/ true));

llvm/lib/MC/MCAsmStreamer.cpp

MCAsmStreamer(MCContext &Context, std::unique_ptr<formatted_raw_ostream> os,
                          : nullptr)),
         CommentStream(CommentToEmit), IsVerboseAsm(isVerboseAsm),
         ShowInst(showInst), UseDwarfDirectory(useDwarfDirectory) {
     assert(InstPrinter);
     if (IsVerboseAsm)
         InstPrinter->setCommentStream(CommentStream);
     if (Assembler->getBackendPtr())
       setAllowAutoPadding(Assembler->getBackend().allowAutoPadding());
+
+    Context.setUseNamesOnTempLabels(true);
   }
 
   MCAssembler &getAssembler() { return *Assembler; }
   MCAssembler *getAssemblerPtr() override { return nullptr; }
 
   inline void EmitEOL() {
     // Dump Explicit Comments here.
     emitExplicitComments();

llvm/tools/llvm-mc/llvm-mc.cpp

Str.reset(
                                      /*useDwarfDirectory*/ true, IP,
                                      std::move(CE), std::move(MAB), ShowInst));
 
   } else if (FileType == OFT_Null) {
     Str.reset(TheTarget->createNullStreamer(Ctx));
   } else {
     assert(FileType == OFT_ObjectFile && "Invalid file type!");
 
-    // Don't waste memory on names of temp labels.
-    Ctx.setUseNamesOnTempLabels(false);
-
     if (!Out->os().supportsSeeking()) {
       BOS = std::make_unique<buffer_ostream>(Out->os());
       OS = BOS.get();
     }
 
     MCCodeEmitter *CE = TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx);
     MCAsmBackend *MAB = TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions);
     Str.reset(TheTarget->createMCObjectStreamer(

llvm/tools/llvm-ml/llvm-ml.cpp

Str.reset(
                                      /*useDwarfDirectory*/ true, IP,
                                      std::move(CE), std::move(MAB), ShowInst));
 
   } else if (FileType == OFT_Null) {
     Str.reset(TheTarget->createNullStreamer(Ctx));
   } else {
     assert(FileType == OFT_ObjectFile && "Invalid file type!");
 
-    // Don't waste memory on names of temp labels.
-    Ctx.setUseNamesOnTempLabels(false);
-
     if (!Out->os().supportsSeeking()) {
       BOS = std::make_unique<buffer_ostream>(Out->os());
       OS = BOS.get();
     }
 
     MCCodeEmitter *CE = TheTarget->createMCCodeEmitter(*MCII, *MRI, Ctx);
     MCAsmBackend *MAB = TheTarget->createMCAsmBackend(*STI, *MRI, MCOptions);
     Str.reset(TheTarget->createMCObjectStreamer(