[PATCH] D10979: Update the branch weight metadata in JumpThreading pass.
congh at google.com
Tue Jul 21 13:03:13 PDT 2015
congh added a comment.
In http://reviews.llvm.org/D10979#208776, @davidxl wrote:
> I suggest also adding another test case (documented in the PR -- the one that has problem with jump-threading + loop-rotation + jump-threading).
> This reminds me of a way to do profile sanity check/validation when debug check is turned on:
> 1. compute the BB freq before the pass
> 2. cfg transformation + BB freq update
> 3. branch probability weight update
> 4. recompute BFI using updated weight in 3). The result of 4) should match that of 2).
You mean comparing result from 4) and 1)? What if a CFG node is split? If CFG is modified, we may not be able to find one-to-one BB match. To make a reasonable comparison, we may need to understand what the pass does...
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