[clang] 220e77a - [clang][CodeGenPGO] Don't use an invalid index when region counts disagree

[Nathan Lanza via cfe-commits]

Author: Nathan Lanza
Date: 2023-05-10T22:53:53-04:00
New Revision: 220e77a83af19b3f6c47472596fdaaef8e305927

URL: https://github.com/llvm/llvm-project/commit/220e77a83af19b3f6c47472596fdaaef8e305927
DIFF: https://github.com/llvm/llvm-project/commit/220e77a83af19b3f6c47472596fdaaef8e305927.diff

LOG: [clang][CodeGenPGO] Don't use an invalid index when region counts disagree

If we're using an old instrprof profile and the user passes we can get
Decls with children decl counts not matching the what the profile was
written against. In a particular case I was debugging we have 24 decls
in the AST and 22 decls in the profile. Avoid crashing in this case.

Differential Revision: https://reviews.llvm.org/D149504

Added: 
    

Modified: 
    clang/lib/CodeGen/CodeGenPGO.h

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/CodeGenPGO.h b/clang/lib/CodeGen/CodeGenPGO.h
index 66c93cba4bb0..392ec5a144fe 100644
--- a/clang/lib/CodeGen/CodeGenPGO.h
+++ b/clang/lib/CodeGen/CodeGenPGO.h
@@ -114,7 +114,12 @@ class CodeGenPGO {
       return 0;
     if (!haveRegionCounts())
       return 0;
-    return RegionCounts[(*RegionCounterMap)[S]];
+    // With profiles from a 
diff ering version of clang we can have mismatched
+    // decl counts. Don't crash in such a case.
+    auto Index = (*RegionCounterMap)[S];
+    if (Index >= RegionCounts.size())
+      return 0;
+    return RegionCounts[Index];
   }
 };