[Driver] Support for compressed debug info on Fuchsia

[phosek]

Summary

Pass the --compress-debug-sections=zlib argument to the linker when
the use of compressed debug info is requested.

[phosek]

@mcgrathr Ping.

[mcgrathr]

lgtm, but we should be sure to advise users that their debugging tools may need build adjustments to ensure they support the compressed formats.

[TWeaver]

Hello all,

really sorry but I've had to revert this patch due to failures on the following build bot:

http://lab.llvm.org:8011/#/builders/216/builds/3484

[dyung]

I think the problem here is that if zlib is not available, you won't get the clang command line you expect:

https://lab.llvm.org/buildbot/#/builders/216/builds/3519

Input was:
<<<<<<
             1: clang version 15.0.0 (https://github.com/llvm/llvm-project.git 2d0c897212d0551966b26eae986209ea31c4f032) 
             2: Target: x86_64-unknown-fuchsia 
             3: Thread model: posix 
             4: InstalledDir: c:\buildbot-root\llvm-clang-x86_64-sie-win\build\bin 
             5: clang: warning: cannot compress debug sections (zlib not installed) [-Wdebug-compression-unavailable] 
             6:  "c:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\bin\\clang.exe" "-cc1" "-triple" "x86_64-unknown-fuchsia" "-emit-obj" "--mrelax-relocations" "-disable-free" "-clear-ast-before-backend" "-main-file-name" "fuchsia.c" "-mrelocation-model" "pic" "-pic-level" "2" "-pic-is-pie" "-mframe-pointer=all" "-ffp-contract=on" "-fno-rounding-math" "-mconstructor-aliases" "-funwind-tables=2" "-target-cpu" "x86-64" "-tune-cpu" "generic" "-mllvm" "-treat-scalable-fixed-error-as-warning" "-debugger-tuning=gdb" "-fcoverage-compilation-dir=C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\tools\\clang\\test\\Driver" "-resource-dir" "c:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\lib\\clang\\15.0.0" "-isysroot" "C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\Driver/platform" "-internal-isystem" "c:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\lib\\clang\\15.0.0\\include" "-internal-externc-isystem" "C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\Driver/platform\\include" "-Og" "-fdebug-compilation-dir=C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\tools\\clang\\test\\Driver" "-ferror-limit" "19" "-fsanitize=safe-stack" "-stack-protector" "2" "-fgnuc-version=4.2.1" "-faddrsig" "-D__GCC_HAVE_DWARF2_CFI_ASM=1" "-o" "C:\\Users\\BUILDB~1\\AppData\\Local\\Temp\\lit-tmp-f3r87ykv\\fuchsia-9a49da.o" "-x" "c" "C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\Driver\\fuchsia.c" 
             7:  "c:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\bin\\ld.lld" "-z" "max-page-size=4096" "-z" "now" "-z" "rodynamic" "-z" "separate-loadable-segments" "-z" "rel" "--pack-dyn-relocs=relr" "--sysroot=C:\\buildbot-root\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\Driver/platform" "-pie" "--build-id" "--hash-style=gnu" "--eh-frame-hdr" "-dynamic-linker" "ld.so.1" "-o" "a.out" "Scrt1.o" "-LC:\\buildbot-root\\llvm-clang-x86_64-sie-win\\llvm-project\\clang\\test\\Driver/platform\\lib" "--compress-debug-sections=zlib" "C:\\Users\\BUILDB~1\\AppData\\Local\\Temp\\lit-tmp-f3r87ykv\\fuchsia-9a49da.o" "c:\\buildbot-root\\llvm-clang-x86_64-sie-win\\build\\lib\\clang\\15.0.0\\lib\\fuchsia\\libclang_rt.builtins-x86_64.a" "-lc" 
>>>>>>

Since lld does produce the expected argument, it suggests that maybe LLD isn't doing any detection of whether zlib is available like the compiler is.

[probinson]

Lit is aware of zlib's presence or absence, you could use REQUIRES: zlib (or you might factor that bit out into its own test with the REQUIRES).

[phosek]

In D114115#3477967, @probinson wrote:

Lit is aware of zlib's presence or absence, you could use REQUIRES: zlib (or you might factor that bit out into its own test with the REQUIRES).

I have moved that test to clang/test/Driver/compress.c which already has REQUIRES: zlib.

clang/lib/Driver/ToolChains/Fuchsia.cpp

void fuchsia::Linker::ConstructJob(Compilation &C, const JobAction &JA,
   ToolChain.AddFilePathLibArgs(Args, CmdArgs);
 
   if (D.isUsingLTO()) {
     assert(!Inputs.empty() && "Must have at least one input.");
     addLTOOptions(ToolChain, Args, CmdArgs, Output, Inputs[0],
                   D.getLTOMode() == LTOK_Thin);
   }
 
+  addLinkerCompressDebugSectionsOption(ToolChain, Args, CmdArgs);
   AddLinkerInputs(ToolChain, Inputs, Args, CmdArgs, JA);
 
   if (!Args.hasArg(options::OPT_nostdlib, options::OPT_nodefaultlibs,
                    options::OPT_r)) {
     if (Args.hasArg(options::OPT_static))
       CmdArgs.push_back("-Bdynamic");
 
     if (D.CCCIsCXX()) {

clang/test/Driver/fuchsia.c

 // RUN:     -flto=thin -flto-jobs=8 2>&1 \
 // RUN:     -fuse-ld=lld \
 // RUN:     | FileCheck %s -check-prefix=CHECK-THINLTO
 // CHECK-THINLTO: "-plugin-opt=mcpu=x86-64"
 // CHECK-THINLTO: "-plugin-opt=thinlto"
 // CHECK-THINLTO: "-plugin-opt=jobs=8"
 
 // RUN: %clang %s -### --target=x86_64-unknown-fuchsia \
+// RUN:     --sysroot=%S/platform \
+// RUN:     -Og -gz 2>&1 \
+// RUN:     | FileCheck %s -check-prefix=CHECK-GZ
+// CHECK-GZ: {{.*}}clang{{.*}}" "--compress-debug-sections=zlib"
+// CHECK-GZ: {{.*}}ld.lld{{.*}}" "--compress-debug-sections=zlib"
+
+// RUN: %clang %s -### --target=x86_64-unknown-fuchsia \
 // RUN:     -gsplit-dwarf -g -c %s 2>&1 \
 // RUN:     | FileCheck %s -check-prefix=CHECK-SPLIT-DWARF
 // CHECK-SPLIT-DWARF: "-split-dwarf-output" "fuchsia.dwo"
 
 // RUN: %clang %s -### --target=aarch64-unknown-fuchsia \
 // RUN:     -fprofile-instr-generate -fcoverage-mapping \
 // RUN:     -resource-dir=%S/Inputs/resource_dir_with_per_target_subdir \
 // RUN:     -fuse-ld=lld 2>&1 \