Don't emit a directory entry for the value in DW_AT_comp_dir, that is always

implied by directory index zero.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@143570 91177308-0d34-0410-b5e6-96231b3b80d8

4 files changed, 29 insertions, 5 deletions

diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
index 1d5e05d8fd..0f4ea051a2 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
@@ -442,6 +442,10 @@ unsigned DwarfDebug::GetOrCreateSourceID(StringRef FileName,
   if (FileName.empty())
     return GetOrCreateSourceID("<stdin>", StringRef());
 
+  // TODO: this might not belong here. See if we can factor this better.
+  if (DirName == CompilationDir)
+    DirName = "";
+
   unsigned SrcId = SourceIdMap.size()+1;
   std::pair<std::string, std::string> SourceName =
       std::make_pair(FileName, DirName);
@@ -466,8 +470,8 @@ unsigned DwarfDebug::GetOrCreateSourceID(StringRef FileName,
 CompileUnit *DwarfDebug::constructCompileUnit(const MDNode *N) {
   DICompileUnit DIUnit(N);
   StringRef FN = DIUnit.getFilename();
-  StringRef Dir = DIUnit.getDirectory();
-  unsigned ID = GetOrCreateSourceID(FN, Dir);
+  CompilationDir = DIUnit.getDirectory();
+  unsigned ID = GetOrCreateSourceID(FN, CompilationDir);
 
   DIE *Die = new DIE(dwarf::DW_TAG_compile_unit);
   CompileUnit *NewCU = new CompileUnit(ID, Die, Asm, this);
@@ -486,8 +490,8 @@ CompileUnit *DwarfDebug::constructCompileUnit(const MDNode *N) {
   else
     NewCU->addUInt(Die, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4, 0);
 
-  if (!Dir.empty())
-    NewCU->addString(Die, dwarf::DW_AT_comp_dir, Dir);
+  if (!CompilationDir.empty())
+    NewCU->addString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
   if (DIUnit.isOptimized())
     NewCU->addUInt(Die, dwarf::DW_AT_APPLE_optimized, dwarf::DW_FORM_flag, 1);
 
diff --git a/lib/CodeGen/AsmPrinter/DwarfDebug.h b/lib/CodeGen/AsmPrinter/DwarfDebug.h
index b280fbb930..d5ce6969e8 100644
--- a/lib/CodeGen/AsmPrinter/DwarfDebug.h
+++ b/lib/CodeGen/AsmPrinter/DwarfDebug.h
@@ -302,6 +302,10 @@ class DwarfDebug {
   MCSymbol *DwarfDebugLocSectionSym;
   MCSymbol *FunctionBeginSym, *FunctionEndSym;
 
+  // As an optimization, there is no need to emit an entry in the directory
+  // table for the same directory as DW_at_comp_dir.
+  StringRef CompilationDir;
+
 private:
 
   /// assignAbbrevNumber - Define a unique number for the abbreviation.
diff --git a/test/CodeGen/X86/dbg-file-name.ll b/test/CodeGen/X86/dbg-file-name.ll
index 70e0a5d1c4..adf9854610 100644
--- a/test/CodeGen/X86/dbg-file-name.ll
+++ b/test/CodeGen/X86/dbg-file-name.ll
@@ -1,7 +1,7 @@
 ; RUN: llc -enable-dwarf-directory -mtriple x86_64-apple-darwin10.0.0  < %s | FileCheck %s
 
 ; Radar 8884898
-; CHECK: file	1 "/Users/manav/one/two" "simple.c"
+; CHECK: file	1 "simple.c"
 
 declare i32 @printf(i8*, ...) nounwind
 
diff --git a/test/CodeGen/X86/dwarf-comp-dir.ll b/test/CodeGen/X86/dwarf-comp-dir.ll
new file mode 100644
index 0000000000..c64752c952
--- /dev/null
+++ b/test/CodeGen/X86/dwarf-comp-dir.ll
@@ -0,0 +1,16 @@
+; RUN: llc %s -o %t -filetype=obj
+; RUN: llvm-dwarfdump %t | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{i32 720913, i32 0, i32 12, metadata !"empty.c", metadata !"/home/nlewycky", metadata !"clang version 3.1 (trunk 143523)", i1 true, i1 true, metadata !"", i32 0, metadata !1, metadata !1, metadata !1, metadata !1} ; [ DW_TAG_compile_unit ]
+!1 = metadata !{metadata !2}
+!2 = metadata !{i32 0}
+
+; The important part of the following check is that dir = #0.
+;                        Dir  Mod Time   File Len   File Name
+;                        ---- ---------- ---------- ---------------------------
+; CHECK: file_names[  1]    0 0x00000000 0x00000000 empty.c