[PATCH] D124088: perf: Fix profile reading to correctly take segments into account.

[Tamar Christina via Phabricator via llvm-commits]

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  LNT's perf parsing implementation has a very subtle bug horrible bug:
  
  It's assuming that the text segment starts at the same address that
  the program was loaded at.  Or rather, it assumes the text segment is
  at address 0.
  
  This is usually not the case (and indeed LLD itself puts many non-exec
  Segments before the first exec one)
  
  Because of this no event is matched for certain binaries.  Also the
  code can wrongly try to attribute an event to the wrong MMAP because
  it only checks the starting address.  This means that the order of the
  MMAPs matters and again as of a few days ago the order coming out of
  LLD places the binary itself after most SOs including ld.so.
  
  By checking only the start address we can attribute an event to an SO
  instead of to the program since trivially shared libraries are
  loaded before the program itself in the virtual memory space.  This
  would later fail to resolve but we'd lose the event.
  
  This patch changes it to also check for the ending position.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D124088

Files:
  lnt/testing/profile/cPerf.cpp

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