[clang] [clang] Optimize SourceManager.getSpellingLocSlowCase and SourceManager.getFileLocSlowCase (PR #164269)

[via cfe-commits]

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@@ -908,19 +908,23 @@ getExpansionLocSlowCase(SourceLocation Loc) const {
 
 SourceLocation SourceManager::getSpellingLocSlowCase(SourceLocation Loc) const {
   do {
-    FileIDAndOffset LocInfo = getDecomposedLoc(Loc);
-    Loc = getSLocEntry(LocInfo.first).getExpansion().getSpellingLoc();
-    Loc = Loc.getLocWithOffset(LocInfo.second);
+    const SLocEntry &Entry = getSLocEntry(getFileID(Loc));
+    Loc = Entry.getExpansion().getSpellingLoc().getLocWithOffset(
+        Loc.getOffset() - Entry.getOffset());
   } while (!Loc.isFileID());
   return Loc;
 }
 
 SourceLocation SourceManager::getFileLocSlowCase(SourceLocation Loc) const {
   do {
-    if (isMacroArgExpansion(Loc))
-      Loc = getImmediateSpellingLoc(Loc);
-    else
-      Loc = getImmediateExpansionRange(Loc).getBegin();
+    const SLocEntry &Entry = getSLocEntry(getFileID(Loc));
+    const ExpansionInfo &ExpInfo = Entry.getExpansion();
+    if (ExpInfo.isMacroArgExpansion()) {
+      Loc = ExpInfo.getSpellingLoc().getLocWithOffset(Loc.getOffset() -
+                                                      Entry.getOffset());
+    } else {
+      Loc = ExpInfo.getExpansionLocStart();
+    }
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SergejSalnikov wrote:

I've tested the following 3 PRs together, but I don't know how to interpret the results.
https://github.com/llvm/llvm-project/pull/163982
https://github.com/llvm/llvm-project/pull/164269
https://github.com/llvm/llvm-project/pull/163982
<img width="1514" height="799" alt="image" src="https://github.com/user-attachments/assets/d7583fa2-f1a0-4158-b231-bca2d8f283de" />


https://github.com/llvm/llvm-project/pull/164269