[DWARF] Unclamp line table version on Darwin for v5 and later.

[JDevlieghere]

Summary

On Darwin we pin the DWARF line tables to version 2. Stop doing so for
DWARF v5 and later.

[aprantl]

llvm/test/CodeGen/Generic/dwarf-md5.ll

5

why does this still work? Wouldn't it yield a DWARF v2 linetable on darwin?

[JDevlieghere]

llvm/test/CodeGen/Generic/dwarf-md5.ll

5

Yup, but the check-lines are identical for version 4 and 2. If you dwarfdump the object file you'll find it's indeed version 2.

dwarf-md5.ll.tmp4.o: file format Mach-O 64-bit x86-64
.debug_line contents:
debug_line[0x00000000]
Line table prologue:
    total_length: 0x00000029
    version: 2

[JDevlieghere]

Add comment to tests explaining why this works on Darwin.

@aprantl Does this LGTY?

[aprantl]

Looks right.

llvm/lib/MC/MCDwarf.cpp

MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
   // Create a symbol for the end of the section (to be set when we get there).
   MCSymbol *LineEndSym = context.createTempSymbol();
 
   // The first 4 bytes is the total length of the information for this
   // compilation unit (not including these 4 bytes for the length).
   emitAbsValue(*MCOS,
                MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym, 4), 4);
 
-  // Next 2 bytes is the Version.
-  // FIXME: On Darwin we still default to V2.
   unsigned LineTableVersion = context.getDwarfVersion();
-  if (context.getObjectFileInfo()->getTargetTriple().isOSDarwin())
+
+  // On Darwin we default to v2 for anything before DWARF v5.
+  if (context.getObjectFileInfo()->getTargetTriple().isOSDarwin() &&
+      LineTableVersion < 5)
     LineTableVersion = 2;
+
+  // Next 2 bytes is the Version.
   MCOS->EmitIntValue(LineTableVersion, 2);
 
   // Keep track of the bytes between the very start and where the header length
   // comes out.
   unsigned PreHeaderLengthBytes = 4 + 2;
 
   // In v5, we get address info next.
   if (LineTableVersion >= 5) {

llvm/test/CodeGen/Generic/dwarf-md5.ll

 ; MD5 checksums provided by IR should be passed through to asm.
 ; They'll be emitted to an object file only for DWARF 5 or later.
 
-; Darwin clamps the line table at DWARF v2 so XFAIL this test.
-; XFAIL: darwin
-
 ; REQUIRES: object-emission
 ; RUN: %llc_dwarf -dwarf-version 4 -filetype=asm -o - %s | FileCheck %s --check-prefix=ASM-4
 ; RUN: %llc_dwarf -dwarf-version 5 -filetype=asm -o - %s | FileCheck %s --check-prefix=ASM-5
 ; RUN: %llc_dwarf -dwarf-version 4 -filetype=obj -o %t4.o %s
 ; RUN: llvm-dwarfdump -debug-line %t4.o | FileCheck %s --check-prefix=OBJ
 ; RUN: %llc_dwarf -dwarf-version 5 -filetype=obj -o %t5.o %s
 ; RUN: llvm-dwarfdump -debug-line %t5.o | FileCheck %s --check-prefixes=OBJ,OBJ-5
 
 ; ASM-4-NOT: .file 0
 ; ASM-4: .file 1 "/scratch{{.*[/\\]}}t1.h"

llvm/test/CodeGen/Generic/dwarf-source.ll

 ; Source text provided by IR should be passed through to asm.
 ; It is emitted to an object file only for DWARF 5 or later.
 
-; Darwin clamps the line table at DWARF v2 so XFAIL this test.
-; XFAIL: darwin
-
 ; REQUIRES: object-emission
 ; RUN: %llc_dwarf -dwarf-version 4 -filetype=asm -o - %s | FileCheck %s --check-prefix=ASM-4
 ; RUN: %llc_dwarf -dwarf-version 5 -filetype=asm -o - %s | FileCheck %s --check-prefix=ASM-5
 ; RUN: %llc_dwarf -dwarf-version 4 -filetype=obj -o %t4.o %s
 ; RUN: llvm-dwarfdump -debug-line %t4.o | FileCheck %s --check-prefixes=OBJ,OBJ-4
 ; RUN: %llc_dwarf -dwarf-version 5 -filetype=obj -o %t5.o %s
 ; RUN: llvm-dwarfdump -debug-line %t5.o | FileCheck %s --check-prefixes=OBJ,OBJ-5
 

llvm/test/MC/ELF/dwarf-file0.s

 # REQUIRES: default_triple
 # RUN: llvm-mc -dwarf-version 4 %s -filetype=obj -o - | llvm-dwarfdump -debug-line - | FileCheck %s --check-prefixes=CHECK,CHECK-4
 # RUN: llvm-mc -dwarf-version 4 %s -filetype=asm -o - | FileCheck %s --check-prefixes=ASM,ASM-4
 # RUN: llvm-mc -dwarf-version 4 %s -filetype=asm -o - 2>&1 | FileCheck %s --check-prefix=WARN
 # RUN: llvm-mc -dwarf-version 5 %s -filetype=obj -o - | llvm-dwarfdump -debug-line - | FileCheck %s --check-prefixes=CHECK,CHECK-5
 # RUN: llvm-mc -dwarf-version 5 %s -filetype=asm -o - | FileCheck %s --check-prefixes=ASM,ASM-5
-# Darwin is stuck on DWARF v2.
-# XFAIL: darwin
         .file 0 "/test" "root.cpp"
         .file 1 "/include" "header.h"
         .file 2 "/test" "root.cpp"
 # CHECK-5:     include_directories[ 0] = "/test"
 # CHECK-4-NOT: include_directories[ 0]
 # CHECK:       include_directories[ 1] = "/include"
 # CHECK-4:     include_directories[ 2] = "/test"
 # CHECK-NOT:   include_directories

llvm/test/MC/ELF/dwarf-loc0.s

 # REQUIRES: default_triple
 # RUN: llvm-mc -dwarf-version 5 %s -filetype=obj -o - | llvm-dwarfdump -debug-line - | FileCheck %s
 # RUN: not llvm-mc -dwarf-version 4 %s -filetype=asm -o - 2>&1 | FileCheck %s -check-prefix=ERR
-# Darwin line table is stuck on DWARF v2.
-# XFAIL: darwin
 # Show that ".loc 0" works in DWARF v5, gets an error for earlier versions.
         .file 0 "root.cpp"
         .file 1 "header.h"
   .loc  0 10 0
         .byte 0
         .loc  1 20 0
         .byte 0