davidxl added a comment.

We may also need to bump both the raw and index format version with this 
change. For the profile use side, we also need to keep the hashing scheme of 
the older version (in profile-use side).  More details to come.

Many tests can also be enhanced to filter out the hash details if they are not 
part the main test.



================
Comment at: llvm/lib/Transforms/Instrumentation/PGOInstrumentation.cpp:623
 // Compute Hash value for the CFG: the lower 32 bits are CRC32 of the index
-// value of each BB in the CFG. The higher 32 bits record the number of edges.
+// value of each BB in the CFG. The higher 32 bits are the CR32 of the numbers
+// of selects, indirect calls, mem ops and edges.
----------------
MaskRay wrote:
> To make sure I understand: we use two CRCs instead of one CRC because we want 
> to extract low/high 32 bits for debugging purposes?
> 
> Otherwise, we can just use one CRC.
JamCRC produces a 32bit value.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D84782/new/

https://reviews.llvm.org/D84782

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