[BOLT] Fix DWARF4/5 file index handling in debug info functions

[grigorypas]

Fix incorrect file index handling that differed between DWARF4 and DWARF5.

DWARF4 file indices start at 1, while DWARF5 starts at 0. The code was
manually adjusting indices with Row.File - 1, which works for DWARF4
but breaks DWARF5.

Replace manual indexing with getFileNameEntry() which abstracts away
the DWARF version differences.

Fixed in:

• printDebugInfo()
• addDebugFilenameToUnit()

[llvmbot]

@llvm/pr-subscribers-bolt

Author: Grigory Pastukhov (grigorypas)

Changes

This PR fixes 3 failing tests on the master branch.

1. FileIndex starts from 1 in DWARF4 and from 0 in DWARF5. getFileNameEntry function abstracts that logic away.
2. perf_test.lds was crashing because the address of the first section was too low.

---

Full diff: https://github.com/llvm/llvm-project/pull/151401.diff

2 Files Affected:

• (modified) bolt/lib/Core/BinaryContext.cpp (+7-11)
• (modified) bolt/test/perf2bolt/Inputs/perf_test.lds (+5-6)

diff --git a/bolt/lib/Core/BinaryContext.cpp b/bolt/lib/Core/BinaryContext.cpp
index 84f1853469709..3f6d27c751556 100644
--- a/bolt/lib/Core/BinaryContext.cpp
+++ b/bolt/lib/Core/BinaryContext.cpp
@@ -1568,23 +1568,19 @@ unsigned BinaryContext::addDebugFilenameToUnit(const uint32_t DestCUID,
   DWARFCompileUnit *SrcUnit = DwCtx->getCompileUnitForOffset(SrcCUID);
   const DWARFDebugLine::LineTable *LineTable =
       DwCtx->getLineTableForUnit(SrcUnit);
-  const std::vector<DWARFDebugLine::FileNameEntry> &FileNames =
-      LineTable->Prologue.FileNames;
-  // Dir indexes start at 1, as DWARF file numbers, and a dir index 0
+  const DWARFDebugLine::FileNameEntry &FileNameEntry =
+      LineTable->Prologue.getFileNameEntry(FileIndex);
+  // Dir indexes start at 1 and a dir index 0
   // means empty dir.
-  assert(FileIndex > 0 && FileIndex <= FileNames.size() &&
-         "FileIndex out of range for the compilation unit.");
   StringRef Dir = "";
-  if (FileNames[FileIndex - 1].DirIdx != 0) {
+  if (FileNameEntry.DirIdx != 0) {
     if (std::optional<const char *> DirName = dwarf::toString(
-            LineTable->Prologue
-                .IncludeDirectories[FileNames[FileIndex - 1].DirIdx - 1])) {
+            LineTable->Prologue.IncludeDirectories[FileNameEntry.DirIdx - 1])) {
       Dir = *DirName;
     }
   }
   StringRef FileName = "";
-  if (std::optional<const char *> FName =
-          dwarf::toString(FileNames[FileIndex - 1].Name))
+  if (std::optional<const char *> FName = dwarf::toString(FileNameEntry.Name))
     FileName = *FName;
   assert(FileName != "");
   DWARFCompileUnit *DstUnit = DwCtx->getCompileUnitForOffset(DestCUID);
@@ -1925,7 +1921,7 @@ static void printDebugInfo(raw_ostream &OS, const MCInst &Instruction,
   const DWARFDebugLine::Row &Row = LineTable->Rows[RowRef.RowIndex - 1];
   StringRef FileName = "";
   if (std::optional<const char *> FName =
-          dwarf::toString(LineTable->Prologue.FileNames[Row.File - 1].Name))
+          dwarf::toString(LineTable->Prologue.getFileNameEntry(Row.File).Name))
     FileName = *FName;
   OS << " # debug line " << FileName << ":" << Row.Line;
   if (Row.Column)
diff --git a/bolt/test/perf2bolt/Inputs/perf_test.lds b/bolt/test/perf2bolt/Inputs/perf_test.lds
index 66d925a05bebc..c2704d73a638c 100644
--- a/bolt/test/perf2bolt/Inputs/perf_test.lds
+++ b/bolt/test/perf2bolt/Inputs/perf_test.lds
@@ -1,13 +1,12 @@
 SECTIONS {
-  . = SIZEOF_HEADERS;
+  . = 0x400000 + SIZEOF_HEADERS;
   .interp : { *(.interp) }
   .note.gnu.build-id : { *(.note.gnu.build-id) }
-  . = 0x212e8;
   .dynsym         : { *(.dynsym) }
-  . = 0x31860;
+  . = 0x801000;
   .text : { *(.text*) }
-  . = 0x41c20;
+  . = 0x803000;
   .fini_array : { *(.fini_array) }
-  . = 0x54e18;
+  . = 0x805000;
   .data : { *(.data) }
-}
\ No newline at end of file
+}

[ayermolo]

Can you add which tests were failing, and why did they start to fail?
Is test change related to this change? Seems unrelated.

[grigorypas]

Can you add which tests were failing, and why did they start to fail? Is test change related to this change? Seems unrelated.

Moved fix to failing test unrelated to the code changes to a separate PR (#154209).

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[ayermolo]

See if Inputs/dwarf5_main.s and Inputs/dwarf5_helper.s
can be re-used.