[llvm] [BOLT] Report flow conservation scores (PR #127954)

[Maksim Panchenko via llvm-commits]

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+## Check profile quality stats reporting
+RUN: yaml2obj %p/Inputs/blarge_new.yaml &> %t.exe
+RUN: llvm-bolt %t.exe -o %t.out --pa -p %p/Inputs/blarge_new.preagg.txt | FileCheck %s
+CHECK: among the hottest 5 functions top 5% function CFG discontinuity is 100.00%
+CHECK: among the hottest 5 functions top 5% call graph flow conservation gap is 60.00%
+CHECK: among the hottest 5 functions top 5% CFG flow conservation gap is 45.53% (weighted) and 96.87% (worst)
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maksfb wrote:

@ShatianWang, does it make sense to group stats? I.e. add stats after a header that says `profile quality metrics for hottest/top N functions...`.

https://github.com/llvm/llvm-project/pull/127954