DebugInfo: Support for compressed debug info sections

1) When creating a .debug_* section and instead create a .zdebug_
   section.
2) When creating a fragment in a .zdebug_* section, make it a compressed
   fragment.
3) When computing the size of a compressed section, compress the data
   and use the size of the compressed data.
4) Emit the compressed bytes.

Also, check that only if a section has a compressed fragment, then that
is the only fragment in the section.

Assert-fail if the fragment's data is modified after it is compressed.

Initial review on llvm-commits by Eric Christopher and Rafael Espindola.

llvm-svn: 204958

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/tools/llvm-mc/llvm-mc.cpp b/llvm/tools/llvm-mc/llvm-mc.cpp
index a4b4a844f67..b2e7a81488d 100644
--- a/llvm/tools/llvm-mc/llvm-mc.cpp
+++ b/llvm/tools/llvm-mc/llvm-mc.cpp
@@ -50,6 +50,9 @@ 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<bool>
 ShowInst("show-inst", cl::desc("Show internal instruction representation"));
 
 static cl::opt<bool>
@@ -381,6 +384,9 @@ 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)
+    MAI->setCompressDebugSections(true);
+
   // FIXME: This is not pretty. MCContext has a ptr to MCObjectFileInfo and
   // MCObjectFileInfo needs a MCContext reference in order to initialize itself.
   std::unique_ptr<MCObjectFileInfo> MOFI(new MCObjectFileInfo());