[PATCH] D149504: [clang][CodeGenPGO] Don't use an invalid index when region counts disagree

[Nathan Lanza via Phabricator via cfe-commits]

lanza created this revision.
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If we're using an old instrprof profile and the user passes
`-Wno-profile-instr-out-of-date` then we can get Decls with children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.

There probably isn't a "right" thing to do other than override the users
wish to force using the profiles, but that't the point of that flag in
the first place.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D149504

Files:
  clang/lib/CodeGen/CodeGenPGO.h


Index: clang/lib/CodeGen/CodeGenPGO.h
===================================================================
--- clang/lib/CodeGen/CodeGenPGO.h
+++ clang/lib/CodeGen/CodeGenPGO.h
@@ -114,7 +114,10 @@
       return 0;
     if (!haveRegionCounts())
       return 0;
-    return RegionCounts[(*RegionCounterMap)[S]];
+    auto Index = (*RegionCounterMap)[S];
+    if (Index >= RegionCounts.size())
+      return 0;
+    return RegionCounts[Index];
   }
 };
 


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