[llvm] [BOLT][DWARF] Sort GDBIndexTUEntryVector (PR #101264)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-bolt

Author: Sayhaan Siddiqui (sayhaan)

<details>
<summary>Changes</summary>

Sorts GDBIndexTUEntryVector in decreasing order by hash to ensure determinism when parallelized.

---
Full diff: https://github.com/llvm/llvm-project/pull/101264.diff


3 Files Affected:

- (modified) bolt/include/bolt/Core/GDBIndex.h (+8) 
- (modified) bolt/lib/Core/GDBIndex.cpp (+1-2) 
- (modified) bolt/test/X86/dwarf4-split-gdb-index-types-gdb-generated.test (+4-4) 


``````````diff
diff --git a/bolt/include/bolt/Core/GDBIndex.h b/bolt/include/bolt/Core/GDBIndex.h
index 6604c2a11472d..0ebcf4ecfe99e 100644
--- a/bolt/include/bolt/Core/GDBIndex.h
+++ b/bolt/include/bolt/Core/GDBIndex.h
@@ -53,6 +53,14 @@ class GDBIndex {
   const GDBIndexTUEntryType &getGDBIndexTUEntryVector() const {
     return GDBIndexTUEntryVector;
   }
+
+  /// Sorts entries in GDBIndexTUEntryVector according to the TypeHash.
+  void sortGDBIndexTUEntryVector() {
+    llvm::stable_sort(GDBIndexTUEntryVector, [](const GDBIndexTUEntry &LHS,
+                                                const GDBIndexTUEntry &RHS) {
+      return LHS.TypeHash > RHS.TypeHash;
+    });
+  }
 };
 
 } // namespace bolt
diff --git a/bolt/lib/Core/GDBIndex.cpp b/bolt/lib/Core/GDBIndex.cpp
index 9e6d24167d559..c7fb4889646b4 100644
--- a/bolt/lib/Core/GDBIndex.cpp
+++ b/bolt/lib/Core/GDBIndex.cpp
@@ -23,7 +23,6 @@ void GDBIndex::updateGdbIndexSection(
     DebugARangesSectionWriter &ARangesSectionWriter) {
   if (!BC.getGdbIndexSection())
     return;
-
   // See https://sourceware.org/gdb/onlinedocs/gdb/Index-Section-Format.html
   // for .gdb_index section format.
 
@@ -141,7 +140,7 @@ void GDBIndex::updateGdbIndexSection(
     write64le(Buffer + 8, CUInfo.second.Length + 4);
     Buffer += 16;
   }
-
+  sortGDBIndexTUEntryVector();
   // Rewrite TU CU List, since abbrevs can be different.
   // Entry example:
   // 0: offset = 0x00000000, type_offset = 0x0000001e, type_signature =
diff --git a/bolt/test/X86/dwarf4-split-gdb-index-types-gdb-generated.test b/bolt/test/X86/dwarf4-split-gdb-index-types-gdb-generated.test
index c9b12574caa3a..6caf5870fca02 100644
--- a/bolt/test/X86/dwarf4-split-gdb-index-types-gdb-generated.test
+++ b/bolt/test/X86/dwarf4-split-gdb-index-types-gdb-generated.test
@@ -17,10 +17,10 @@
 # POSTCHECK-NEXT:         0: Offset = 0x0, Length = 0x34
 # POSTCHECK-NEXT:         1: Offset = 0x34, Length = 0x34
 # POSTCHECK:          Types CU list offset = 0x38, has 4 entries
-# POSTCHECK-NEXT:       0: offset = 0x00000000, type_offset = 0x0000001e, type_signature = 0x675d23e4f33235f2
-# POSTCHECK-NEXT:       1: offset = 0x0000004a, type_offset = 0x0000001e, type_signature = 0x49dc260088be7e56
-# POSTCHECK-NEXT:       2: offset = 0x00000000, type_offset = 0x0000001e, type_signature = 0x104ec427d2ebea6f
-# POSTCHECK-NEXT:       3: offset = 0x0000004a, type_offset = 0x0000001e, type_signature = 0xb4580bc1535df1e4
+# POSTCHECK-NEXT:       0: offset = 0x0000004a, type_offset = 0x0000001e, type_signature = 0xb4580bc1535df1e4
+# POSTCHECK-NEXT:       1: offset = 0x00000000, type_offset = 0x0000001e, type_signature = 0x675d23e4f33235f2
+# POSTCHECK-NEXT:       2: offset = 0x0000004a, type_offset = 0x0000001e, type_signature = 0x49dc260088be7e56
+# POSTCHECK-NEXT:       3: offset = 0x00000000, type_offset = 0x0000001e, type_signature = 0x104ec427d2ebea6f
 # POSTCHECK:          Address area offset = 0x98, has 2 entries
 # POSTCHECK-NEXT:         Low/High address = [0x[[#%.4x,ADDR:]],
 # POSTCHECK-SAME:           0x[[#ADDR + 0x7a]]) (Size: 0x7a), CU id = 0

``````````

</details>


https://github.com/llvm/llvm-project/pull/101264