DebugInfo: Add metadata support for disabling DWARF pub sections

In cases where the debugger load time is a worthwhile tradeoff (or less
costly - such as loading from a DWP instead of a variety of DWOs
(possibly over a high-latency/distributed filesystem)) against object
file size, it can be reasonable to disable pubnames and corresponding
gdb-index creation in the linker.

A backend-flag version of this was implemented for NVPTX in
D44385/r327994 - which was fine for NVPTX which wouldn't mix-and-match
CUs. Now that it's going to be a user-facing option (likely powered by
"-gno-pubnames", the same as GCC) it should be encoded in the
DICompileUnit so it can vary per-CU.

After this, likely the NVPTX support should be migrated to the metadata
& the previous flag implementation should be removed.

Reviewers: aprantl

Differential Revision: https://reviews.llvm.org/D50213

llvm-svn: 339939

1 files changed, 10 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
index 20b0b8d3fea..119f65e33f5 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AccelTable.cpp
@@ -23,6 +23,7 @@
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/MC/MCSymbol.h"
 #include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetLoweringObjectFile.h"
 #include <algorithm>
 #include <cstddef>
 #include <cstdint>
@@ -554,12 +555,21 @@ void llvm::emitDWARF5AccelTable(
     const DwarfDebug &DD, ArrayRef<std::unique_ptr<DwarfCompileUnit>> CUs) {
   std::vector<MCSymbol *> CompUnits;
   for (const auto &CU : enumerate(CUs)) {
+    if (CU.value()->getCUNode()->getNameTableKind() ==
+        DICompileUnit::DebugNameTableKind::None)
+      continue;
     assert(CU.index() == CU.value()->getUniqueID());
     const DwarfCompileUnit *MainCU =
         DD.useSplitDwarf() ? CU.value()->getSkeleton() : CU.value().get();
     CompUnits.push_back(MainCU->getLabelBegin());
   }
 
+  if (CompUnits.empty())
+    return;
+
+  Asm->OutStreamer->SwitchSection(
+      Asm->getObjFileLowering().getDwarfDebugNamesSection());
+
   Contents.finalize(Asm, "names");
   Dwarf5AccelTableWriter<DWARF5AccelTableData>(
       Asm, Contents, CompUnits,