[DebugInfo] Fine tune emitting flags as part of the producer

[JDevlieghere]

Summary

When using APPLE extensions, don't duplicate the compiler invocation's
flags both in AT_producer and AT_APPLE_flags.

[aprantl]

Thanks!

[davide]

Lgtm.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

DwarfDebug::getOrCreateDwarfCompileUnit(const DICompileUnit *DIUnit) {
   // compilation directory.
   if (!Asm->OutStreamer->hasRawTextSupport() || SingleCU)
     Asm->OutStreamer->emitDwarfFile0Directive(
         CompilationDir, FN, NewCU.getMD5AsBytes(DIUnit->getFile()),
         DIUnit->getSource(), NewCU.getUniqueID());
 
   StringRef Producer = DIUnit->getProducer();
   StringRef Flags = DIUnit->getFlags();
-  if (!Flags.empty()) {
+  if (!Flags.empty() && !useAppleExtensionAttributes()) {
     std::string ProducerWithFlags = Producer.str() + " " + Flags.str();
     NewCU.addString(Die, dwarf::DW_AT_producer, ProducerWithFlags);
   } else
     NewCU.addString(Die, dwarf::DW_AT_producer, Producer);
 
   NewCU.addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
                 DIUnit->getSourceLanguage());
   NewCU.addString(Die, dwarf::DW_AT_name, FN);

llvm/test/DebugInfo/X86/debug-info-producer-with-flags.ll

 ; RUN: llc -mtriple=x86_64-unknown-linux-gnu %s -o %t -filetype=obj
-; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s --check-prefix LINUX
+; RUN: llc -mtriple=x86_64-apple-macosx %s -o %t -filetype=obj
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s --check-prefix DARWIN
 ;
 ; Test the DW_AT_producer DWARF attribute.
 ; When producer and flags are both given in DIComileUnit, set DW_AT_producer
 ; as two values combined.
 ;
 ; The test splits into two parts, this is LLVM part. The frontend part can be
 ; found at llvm/tools/clang/test/Driver/debug-options.c.
 ;
 ; Generated and reduced from:
 ; clang++ -g -grecord-gcc-switches test.cc -S -llvm-emit -o -
 ;
 ; test.cc:
 ;   int main() {
 ;     return 0;
 ;   }
 
-; CHECK: DW_AT_producer
-; CHECK-SAME: "clang++ -g -grecord-gcc-switches test.cc -S -emit-llvm -o -"
+; LINUX: DW_AT_producer{{.*}}("clang++ -g -grecord-gcc-switches test.cc -S -emit-llvm -o -")
+; DARWIN: DW_AT_producer{{.*}}("clang++")
+; DARWIN: DW_AT_APPLE_flags{{.*}}("-g -grecord-gcc-switches test.cc -S -emit-llvm -o -")
+
 target triple = "x86_64-unknown-linux-gnu"
 
 define i32 @main() !dbg !6 {
 entry:
   %retval = alloca i32, align 4
   store i32 0, i32* %retval, align 4
   ret i32 0, !dbg !10
 }