Recommit r348806: DebugInfo: Use symbol difference for CU length to simplify assembly reading/editing
Mucking about simplifying a test case ( https://reviews.llvm.org/D55261 ) I stumbled across something I've hit before - that LLVM's (GCC's does too, FWIW) assembly output includes a hardcode length for a DWARF unit in its header. Instead we could emit a label difference - making the assembly easier to read/edit (though potentially at a slight (I haven't tried to observe it) performance cost of delaying/sinking the length computation into the MC layer).
Fix: Predicated all the changes (including creating the labels, even if they aren't used/needed) behind the NVPTX useSectionsAsReferences, avoiding emitting labels in NVPTX where ptxas can't parse them.
Reviewers: JDevlieghere, probinson, ABataev
Differential Revision: https://reviews.llvm.org/D55281
llvm-svn: 349430
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
index 062eb3a..991dac7 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp
@@ -1553,7 +1553,14 @@
void DwarfUnit::emitCommonHeader(bool UseOffsets, dwarf::UnitType UT) {
// Emit size of content not including length itself
Asm->OutStreamer->AddComment("Length of Unit");
- Asm->emitInt32(getHeaderSize() + getUnitDie().getSize());
+ if (!DD->useSectionsAsReferences()) {
+ StringRef Prefix = isDwoUnit() ? "debug_info_dwo_" : "debug_info_";
+ MCSymbol *BeginLabel = Asm->createTempSymbol(Prefix + "start");
+ EndLabel = Asm->createTempSymbol(Prefix + "end");
+ Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
+ Asm->OutStreamer->EmitLabel(BeginLabel);
+ } else
+ Asm->emitInt32(getHeaderSize() + getUnitDie().getSize());
Asm->OutStreamer->AddComment("DWARF version number");
unsigned Version = DD->getDwarfVersion();