[PATCH] D115485: [DwarfDebug] Prioritise DWARF filename in debuginfo over MC Target Options

[Andy Wang via Phabricator via llvm-commits]

cbeuw created this revision.
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The value of splitDebugFilename in DICompileUnit is currently ignored when
emitting the dwo name into an object file. The path supplied in
MCOptions.SplitDwarfFile is used both as a real path to write the split
dwo content, and as the value of DW_AT_[GNU_]dwo_name emitted into the object
file.

Instead, the filename specified in DICompileUnit should be the one emitted so
long as it has been specified. Additionally, since MCOptions.SplitDwarfFile
points to a real path, this may lead to inconsistent compilation results when
doing remote/distributed builds.

MCOptions.SplitDwarfFile remains to be used as the real path to write the
dwo file, but splitDebugFilename in DICompileUnit is emitted when specified,
and otherwise falls back to emit MCOptions.SplitDwarfFile as-is


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D115485

Files:
  llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
  llvm/test/DebugInfo/X86/debug-macinfo-split-dwarf.ll
  llvm/test/DebugInfo/dwo-different-name.ll


Index: llvm/test/DebugInfo/dwo-different-name.ll
===================================================================
--- /dev/null
+++ llvm/test/DebugInfo/dwo-different-name.ll
@@ -0,0 +1,16 @@
+; RUN: %llc_dwarf %s -filetype=obj -o %t --split-dwarf-file from-mc-options.dwo
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+; REQUIRES: default_triple, object-emission
+;
+; CHECK: DW_AT_GNU_dwo_name ("from-debuginfo.dwo")
+; CHECK-NOT: DW_AT_GNU_dwo_name ("from-mc-options.dwo")
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "Clang", isOptimized: false, runtimeVersion: 2, splitDebugFilename: "from-debuginfo.dwo", emissionKind: FullDebug, enums: !2, globals: !2, retainedTypes: !5)
+!1 = !DIFile(filename: "<stdin>", directory: "/")
+!2 = !{}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{!6}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
Index: llvm/test/DebugInfo/X86/debug-macinfo-split-dwarf.ll
===================================================================
--- llvm/test/DebugInfo/X86/debug-macinfo-split-dwarf.ll
+++ llvm/test/DebugInfo/X86/debug-macinfo-split-dwarf.ll
@@ -44,7 +44,7 @@
 !llvm.module.flags = !{!21, !22, !23}
 !llvm.ident = !{!24}
 
-!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, splitDebugFilename: "debug-macro-split-dwarf.dwo", emissionKind: FullDebug, enums: !2, macros: !3, nameTableKind: GNU)
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 10.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, macros: !3, nameTableKind: GNU)
 !1 = !DIFile(filename: "debug-macro-split-dwarf.c", directory: "/", checksumkind: CSK_MD5, checksum: "e74d0fa8f714535c1bac6da2ffbbd898")
 !2 = !{}
 !3 = !{!4, !14, !15, !16, !17, !18, !19, !20}
Index: llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
===================================================================
--- llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -1247,10 +1247,12 @@
                                          ? dwarf::DW_AT_dwo_name
                                          : dwarf::DW_AT_GNU_dwo_name;
       finishUnitAttributes(TheCU.getCUNode(), TheCU);
-      TheCU.addString(TheCU.getUnitDie(), attrDWOName,
-                      Asm->TM.Options.MCOptions.SplitDwarfFile);
-      SkCU->addString(SkCU->getUnitDie(), attrDWOName,
-                      Asm->TM.Options.MCOptions.SplitDwarfFile);
+      StringRef embeddedDWOName = TheCU.getCUNode()->getSplitDebugFilename();
+      if (embeddedDWOName.empty()) {
+        embeddedDWOName = Asm->TM.Options.MCOptions.SplitDwarfFile;
+      }
+      TheCU.addString(TheCU.getUnitDie(), attrDWOName, embeddedDWOName);
+      SkCU->addString(SkCU->getUnitDie(), attrDWOName, embeddedDWOName);
       // Emit a unique identifier for this CU.
       uint64_t ID =
           DIEHash(Asm, &TheCU).computeCUSignature(DWOName, TheCU.getUnitDie());


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