[llvm-mc] - Teach llvm-mc to generate zlib styled compression sections.

This patch is strongly based on previously reverted D20331.
(because of gnuutils < 2.26 does not support compressed debug sections in non zlib-gnu style)

Difference that this patch supports both zlib and zlib-gnu styles.

-compress-debug-sections option now supports next values:

-compress-debug-sections=zlib-gnu
-compress-debug-sections=zlib
-compress-debug-sections=none
Previously specifying -compress-debug-sections enabled zlib-gnu compression,
so anyone can put "-compress-debug-sections=zlib-gnu" to restore the behavior
that was before this patch for case when compression was enabled.

Differential revision: http://reviews.llvm.org/D20676

llvm-svn: 270977

1 files changed, 14 insertions, 5 deletions

diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index 9ea8f2ef433..d9e3798ee88 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -52,9 +52,18 @@ OutputFilename("o", cl::desc("Output filename"),
 static cl::opt<bool>
 ShowEncoding("show-encoding", cl::desc("Show instruction encodings"));
 
-static cl::opt<bool>
-CompressDebugSections("compress-debug-sections",
-                      cl::desc("Compress DWARF debug sections"));
+static cl::opt<DebugCompressionType>
+CompressDebugSections("compress-debug-sections", cl::ValueOptional,
+  cl::init(DebugCompressionType::DCT_None),
+  cl::desc("Choose DWARF debug sections compression:"),
+  cl::values(
+    clEnumValN(DebugCompressionType::DCT_None, "none",
+      "No compression"),
+    clEnumValN(DebugCompressionType::DCT_Zlib, "zlib",
+      "Use zlib compression"),
+    clEnumValN(DebugCompressionType::DCT_ZlibGnu, "zlib-gnu",
+      "Use zlib-gnu compression (depricated)"),
+    clEnumValEnd));
 
 static cl::opt<bool>
 ShowInst("show-inst", cl::desc("Show internal instruction representation"));
@@ -407,13 +416,13 @@ int main(int argc, char **argv) {
   std::unique_ptr<MCAsmInfo> MAI(TheTarget->createMCAsmInfo(*MRI, TripleName));
   assert(MAI && "Unable to create target asm info!");
 
-  if (CompressDebugSections) {
+  if (CompressDebugSections != DebugCompressionType::DCT_None) {
     if (!zlib::isAvailable()) {
       errs() << ProgName
              << ": build tools with zlib to enable -compress-debug-sections";
       return 1;
     }
-    MAI->setCompressDebugSections(true);
+    MAI->setCompressDebugSections(CompressDebugSections);
   }
 
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and