[llvm] [BOLT] Fix failing tests by refactoring access to FileNameEntry to make it DWAFR version agnostic (PR #151401)

[Grigory Pastukhov via llvm-commits]

https://github.com/grigorypas created https://github.com/llvm/llvm-project/pull/151401

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. 

>From 3d427e60747a5d9f8b24993f0679fc13baf6f55c Mon Sep 17 00:00:00 2001
From: Grigory Pastukhov <gpastukhov at meta.com>
Date: Wed, 30 Jul 2025 14:44:29 -0700
Subject: [PATCH] Use getFileNameEntry for retrieving FileNameEntry DWARF
 version agnositc way

---
 bolt/lib/Core/BinaryContext.cpp          | 18 +++++++-----------
 bolt/test/perf2bolt/Inputs/perf_test.lds | 11 +++++------
 2 files changed, 12 insertions(+), 17 deletions(-)

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
+}