[Driver] Use -gdwarf-3 by default for FreeBSD

[MaskRay]

Summary

The imported binutils in base supports DWARF 3.

[emaste]

I'm using this change: https://github.com/emaste/freebsd/commit/1c3deab6d518feb1a7e88de5b342a139e4022a21

In FreeBSD 12 and later we use Clang, lld, and ELF Tool Chain. (We still have gas and objdump from the outdated binutils 2.17.50.)

[MaskRay]

In D50294#1245454, @emaste wrote:

I'm using this change: https://github.com/emaste/freebsd/commit/1c3deab6d518feb1a7e88de5b342a139e4022a21

In FreeBSD 12 and later we use Clang, lld, and ELF Tool Chain. (We still have gas and objdump from the outdated binutils 2.17.50.)

Will you upstream this commit (I can abandon this one)? I created this revision because I was learning clangDriver... I had a vague and probably incorrect impression that some folks said kgdb or dtrace or whatever might not support DWARF 3 or 4.

[emaste]

In D50294#1246980, @MaskRay wrote:

In D50294#1245454, @emaste wrote:

I'm using this change: https://github.com/emaste/freebsd/commit/1c3deab6d518feb1a7e88de5b342a139e4022a21

In FreeBSD 12 and later we use Clang, lld, and ELF Tool Chain. (We still have gas and objdump from the outdated binutils 2.17.50.)

Will you upstream this commit (I can abandon this one)? I created this revision because I was learning clangDriver... I had a vague and probably incorrect impression that some folks said kgdb or dtrace or whatever might not support DWARF 3 or 4.

Hmm, somehow I forgot about this until being reminded by @arichardson just now. I will upstream it.

The primary motivation for staying with DWARF2 was indeed kgdb, based on gdb 6.1.1, and dtrace (specifically dtrace's build tool ctfconvert) also did not support DWARF >2. However, these issues have all been addressed:

1. We're deprecating gdb 6.1.1-based kgdb, using a contemporary gdb port.
2. In any case the kernel is still building with explicit -gdwarf2 today so it doesn't matter anyhow, there's no need for the toolchain default to be set based on the kernel's needs.
3. DTrace tooling limitations arose as a side effect of our (well, ELF Tool Chain's) libdwarf but it has been updated to handle DWARF4 some time ago.

Perhaps I should just upload a new diff to this review?

[MaskRay]

Abandon due to D66760

lib/Driver/ToolChains/FreeBSD.h

void addLibStdCxxIncludePaths(
       llvm::opt::ArgStringList &CC1Args) const override;
   void AddCXXStdlibLibArgs(const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs) const override;
 
   llvm::ExceptionHandling GetExceptionModel(
       const llvm::opt::ArgList &Args) const override;
   bool isPIEDefault() const override;
   SanitizerMask getSupportedSanitizers() const override;
-  unsigned GetDefaultDwarfVersion() const override { return 2; }
+  unsigned GetDefaultDwarfVersion() const override { return 3; }
   // Until dtrace (via CTF) and LLDB can deal with distributed debug info,
   // FreeBSD defaults to standalone/full debug info.
   bool GetDefaultStandaloneDebug() const override { return true; }
 
 protected:
   Tool *buildAssembler() const override;
   Tool *buildLinker() const override;
 };
 
 } // end namespace toolchains
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_FREEBSD_H

test/CodeGen/dwarf-version.c

 // RUN: %clang -target x86_64-linux-gnu -gdwarf-2 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
 // RUN: %clang -target x86_64-linux-gnu -gdwarf-3 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER3
 // RUN: %clang -target x86_64-linux-gnu -gdwarf-4 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
 // RUN: %clang -target x86_64-linux-gnu -gdwarf-5 -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER5
 // RUN: %clang -target x86_64-linux-gnu -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
 // RUN: %clang -target x86_64-linux-gnu -gdwarf -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4
 
 // The -isysroot is used as a hack to avoid LIT messing with the SDKROOT
 // environment variable which indirecty overrides the version in the target
 // triple used here.
 // RUN: %clang -target x86_64-apple-macosx10.11 -g -S -emit-llvm -o - %s -isysroot %t | FileCheck %s --check-prefix=VER4
 // RUN: %clang -target x86_64-apple-darwin14 -g -S -emit-llvm -o - %s -isysroot %t | FileCheck %s --check-prefix=VER2
 
 // RUN: %clang -target powerpc-unknown-openbsd -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
-// RUN: %clang -target powerpc-unknown-freebsd -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
+// RUN: %clang -target powerpc-unknown-freebsd -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER3
 // RUN: %clang -target i386-pc-solaris -g -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER2
 //
 // Test what -gcodeview and -gdwarf do on Windows.
 // RUN: %clang -target i686-pc-windows-msvc -gcodeview -S -emit-llvm -o - %s | FileCheck %s --check-prefix=NODWARF --check-prefix=CODEVIEW
 // RUN: %clang -target i686-pc-windows-msvc -gdwarf -gcodeview -S -emit-llvm -o - %s | FileCheck %s --check-prefix=VER4 --check-prefix=CODEVIEW
 int main (void) {
   return 0;
 }

test/Driver/clang-g-opts.c

 // RUN: %clang -### -S %s        2>&1 | FileCheck --check-prefix=CHECK-WITHOUT-G %s
 // RUN: %clang -### -S %s -g -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G %s
 
 // Assert that the toolchains which should default to a lower Dwarf version do so.
 // RUN: %clang -### -S %s -g -target x86_64-apple-darwin8 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g -target x86_64-pc-freebsd10.0 2>&1 \
-// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
+// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF3 %s
 
 // 'g0' is the default. Just sanity-test that it does nothing
 // RUN: %clang -### -S %s -g0    2>&1 | FileCheck --check-prefix=CHECK-WITHOUT-G %s
 
 // And check that the last of -g or -g0 wins.
 // RUN: %clang -### -S %s -g -g0 2>&1 | FileCheck --check-prefix=CHECK-WITHOUT-G %s
 
 // These should be semantically the same as not having given 'g0' at all,
 // as the last 'g' option wins.
 //
 // RUN: %clang -### -S %s -g0 -g -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G %s
 // RUN: %clang -### -S %s -g0 -g -target x86_64-apple-darwin8 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-STANDALONE %s
 // RUN: %clang -### -S %s -g0 -g -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 // RUN: %clang -### -S %s -g0 -g -target x86_64-pc-freebsd10.0 2>&1 \
-// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
+// RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF3 %s
 // RUN: %clang -### -S %s -g0 -g -target i386-pc-solaris 2>&1 \
 // RUN:             | FileCheck --check-prefix=CHECK-WITH-G-DWARF2 %s
 
 // CHECK-WITHOUT-G-NOT: -debug-info-kind
 // CHECK-WITH-G: "-debug-info-kind=limited"
 // CHECK-WITH-G: "-dwarf-version=4"
 // CHECK-WITH-G-DWARF2: "-dwarf-version=2"
+// CHECK-WITH-G-DWARF3: "-dwarf-version=3"
 
 // CHECK-WITH-G-STANDALONE: "-debug-info-kind=standalone"
 // CHECK-WITH-G-STANDALONE: "-dwarf-version=2"

test/Driver/debug-options.c

 // RUN:             | FileCheck -check-prefix=GLTO_ONLY %s
 // RUN: %clang -### -c -gline-tables-only %s 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY %s
 // RUN: %clang -### -c -gline-tables-only %s -target x86_64-apple-darwin 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY %s
 // RUN: %clang -### -c -gline-tables-only %s -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_ONLY_DWARF2 %s
 // RUN: %clang -### -c -gline-tables-only %s -target x86_64-pc-freebsd10.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=GLTO_ONLY_DWARF2 %s
+// RUN:             | FileCheck -check-prefix=GLTO_ONLY_DWARF3 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-linux-gnu 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_ONLY %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-apple-darwin16 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_STANDALONE -check-prefix=G_DWARF4 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target i686-pc-openbsd 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target x86_64-pc-freebsd10.0 2>&1 \
-// RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
+// RUN:             | FileCheck -check-prefix=G_ONLY_DWARF3 %s
 // RUN: %clang -### -c -gline-tables-only -g %s -target i386-pc-solaris 2>&1 \
 // RUN:             | FileCheck -check-prefix=G_ONLY_DWARF2 %s
 // RUN: %clang -### -c -gline-tables-only -g0 %s 2>&1 \
 // RUN:             | FileCheck -check-prefix=GLTO_NO %s
 //
 // RUN: %clang -### -c -grecord-gcc-switches %s 2>&1 \
 //             | FileCheck -check-prefix=GRECORD %s
 // RUN: %clang -### -c -gno-record-gcc-switches %s 2>&1 \

 // GLTO_ONLY-NOT: "-dwarf-ext-refs"
 // GLTO_ONLY: "-debug-info-kind=line-tables-only"
 // GLTO_ONLY-NOT: "-dwarf-ext-refs"
 //
 // GLTO_ONLY_DWARF2: "-cc1"
 // GLTO_ONLY_DWARF2: "-debug-info-kind=line-tables-only"
 // GLTO_ONLY_DWARF2: "-dwarf-version=2"
 //
+// GLTO_ONLY_DWARF3: "-cc1"
+// GLTO_ONLY_DWARF3: "-debug-info-kind=line-tables-only"
+// GLTO_ONLY_DWARF3: "-dwarf-version=3"
+//
 // G_ONLY: "-cc1"
 // G_ONLY: "-debug-info-kind=limited"
 //
 // These tests assert that "-gline-tables-only" "-g" uses the latter,
 // but otherwise not caring about the DebugInfoKind.
 // G_ONLY_DWARF2: "-cc1"
 // G_ONLY_DWARF2: "-debug-info-kind={{standalone|limited}}"
 // G_ONLY_DWARF2: "-dwarf-version=2"
 //
+// G_ONLY_DWARF3: "-cc1"
+// G_ONLY_DWARF3: "-debug-info-kind={{standalone|limited}}"
+// G_ONLY_DWARF3: "-dwarf-version=3"
+//
 // G_STANDALONE: "-cc1"
 // G_STANDALONE: "-debug-info-kind=standalone"
 // G_DWARF4: "-dwarf-version=4"
 //
 // G_GDB:  "-debugger-tuning=gdb"
 // G_LLDB: "-debugger-tuning=lldb"
 // G_SCE:  "-debugger-tuning=sce"
 //