[DebugInfo] -fdebug-prefix-map: handle '#line "file"' for asm source

[MaskRay]

Summary

getContext().setMCLineTableRootFile (from D62074) sets RootFile.Name to
FirstCppHashFilename. RootFile.Name is not processed by -fdebug-prefix-map
and will go to DW_TAG_compile_unit's DT_AT_name and DW_TAG_label's
DW_AT_decl_file. Remap RootFile.Name.

Fix another issue reported by https://github.com/llvm/llvm-project/issues/56609

[raj.khem]

I have tested this revision and it fixes the problem I was seeing

[MaskRay]

try fixing Windows path separator

[dblaikie]

SGTM

llvm/include/llvm/MC/MCDwarf.h

void setRootFile(StringRef Directory, StringRef FileName,
     Header.trackMD5Usage(Checksum.has_value());
     Header.HasSource = Source.has_value();
   }
 
   void resetFileTable() { Header.resetFileTable(); }
 
   bool hasRootFile() const { return !Header.RootFile.Name.empty(); }
 
+  MCDwarfFile &getRootFile() { return Header.RootFile; }
   const MCDwarfFile &getRootFile() const { return Header.RootFile; }
 
   // Report whether MD5 usage has been consistent (all-or-none).
   bool isMD5UsageConsistent() const { return Header.isMD5UsageConsistent(); }
 
   MCSymbol *getLabel() const {
     return Header.Label;
   }

llvm/lib/MC/MCContext.cpp

 void MCContext::RemapDebugPaths() {
   const auto &DebugPrefixMap = this->DebugPrefixMap;
   if (DebugPrefixMap.empty())
     return;
 
   // Remap compilation directory.
   remapDebugPath(CompilationDir);
 
-  // Remap MCDwarfDirs in all compilation units.
+  // Remap MCDwarfDirs and RootFile.Name in all compilation units.
   SmallString<256> P;
   for (auto &CUIDTablePair : MCDwarfLineTablesCUMap) {
     for (auto &Dir : CUIDTablePair.second.getMCDwarfDirs()) {
       P = Dir;
       remapDebugPath(P);
       Dir = std::string(P);
     }
+
+    // Used by DW_TAG_compile_unit's DT_AT_name and DW_TAG_label's
+    // DW_AT_decl_file for DWARF v5 generated for assembly source.
+    P = CUIDTablePair.second.getRootFile().Name;
+    remapDebugPath(P);
+    CUIDTablePair.second.getRootFile().Name = std::string(P);
   }
 }
 
 //===----------------------------------------------------------------------===//
 // Dwarf Management
 //===----------------------------------------------------------------------===//
 
 EmitDwarfUnwindType MCContext::emitDwarfUnwindInfo() const {

llvm/test/MC/ELF/debug-hash-file.s

 
 // DWARF5:      include_directories[ 0] =
 // DWARF5-NOT:  include_directories[ 1] =
 // DWARF5:      file_names[ 0]:
 // DWARF5-NEXT:           name: "/MyTest/Inputs/other.S"
 // DWARF5-NEXT:      dir_index: 0
 // DWARF5-NOT:  file_names[ 1]:
 
+// RUN: llvm-mc -triple=x86_64 -filetype=obj -g -dwarf-version=4 -fdebug-prefix-map=/MyTest=/src_root %s -o %t.4.o
+// RUN: llvm-dwarfdump -debug-info -debug-line %t.4.o | FileCheck %s --check-prefixes=MAP,MAP_V4
+// RUN: llvm-mc -triple=x86_64 -filetype=obj -g -dwarf-version=5 -fdebug-prefix-map=/MyTest=/src_root %s -o %t.5.o
+// RUN: llvm-dwarfdump -debug-info -debug-line %t.5.o | FileCheck %s --check-prefixes=MAP,MAP_V5
+
+// MAP-LABEL:   DW_TAG_compile_unit
+// MAP:           DW_AT_name      ("/src_root/Inputs{{(/|\\)+}}other.S")
+// MAP-LABEL:     DW_TAG_label
+// MAP:             DW_AT_decl_file      ("/src_root/Inputs{{(/|\\)+}}other.S")
+
+// MAP_V4:      include_directories[  1] = "/src_root/Inputs"
+// MAP_V4-NEXT: file_names[  1]:
+// MAP_V4-NEXT:            name: "other.S"
+// MAP_V4-NEXT:       dir_index: 1
+
+// MAP_V5:      include_directories[  0] = "{{.*}}"
+// MAP_V5-NEXT: file_names[  0]:
+// MAP_V5-NEXT:            name: "/src_root/Inputs/other.S"
+// MAP_V5-NEXT:       dir_index: 0
+
 # 1 "/MyTest/Inputs/other.S"
 
 foo:
   nop
   nop
   nop