Revert "Revert r305164/5/7."

Restore the `-gz` option to the driver with some minor tweaks to handle
the additional case for `-Wa,--compress-debug-sections`.

This intends to make the compression of the debug information
controllable from the driver.  The following is the behaviour:

  -gz           enable compression (ambiguous for format, will default to zlib-gnu)
  -gz=none      disable compression
  -gz=zlib-gnu  enable compression (deprecated GNU style zlib compression)
  -gz=zlib      enable compression (zlib based compression)

Although -Wa,-compress-debug-sections works, it should be discouraged
when using the driver to invoke the assembler.  However, we permit the
assembler to accept the GNU as style argument --compress-debug-sections
to maintain compatibility.

Note, -gz/-gz= does *NOT* imply -g.  That is, you need to additionally
specific -g for debug information to be generated.

llvm-svn: 306115

1 files changed, 16 insertions, 3 deletions

diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 203723953a6..6254b0013ba 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -745,9 +745,22 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.InstrumentForProfiling = Args.hasArg(OPT_pg);
   Opts.CallFEntry = Args.hasArg(OPT_mfentry);
   Opts.EmitOpenCLArgMetadata = Args.hasArg(OPT_cl_kernel_arg_info);
-  // TODO: map this from -gz in the driver and give it a named value
-  if (Args.hasArg(OPT_compress_debug_sections))
-    Opts.setCompressDebugSections(llvm::DebugCompressionType::GNU);
+
+  if (const Arg *A = Args.getLastArg(OPT_compress_debug_sections,
+                                     OPT_compress_debug_sections_EQ)) {
+    if (A->getOption().getID() == OPT_compress_debug_sections) {
+      // TODO: be more clever about the compression type auto-detection
+      Opts.setCompressDebugSections(llvm::DebugCompressionType::GNU);
+    } else {
+      auto DCT = llvm::StringSwitch<llvm::DebugCompressionType>(A->getValue())
+                     .Case("none", llvm::DebugCompressionType::None)
+                     .Case("zlib", llvm::DebugCompressionType::Z)
+                     .Case("zlib-gnu", llvm::DebugCompressionType::GNU)
+                     .Default(llvm::DebugCompressionType::None);
+      Opts.setCompressDebugSections(DCT);
+    }
+  }
+
   Opts.RelaxELFRelocations = Args.hasArg(OPT_mrelax_relocations);
   Opts.DebugCompilationDir = Args.getLastArgValue(OPT_fdebug_compilation_dir);
   for (auto A : Args.filtered(OPT_mlink_bitcode_file, OPT_mlink_cuda_bitcode)) {