[PATCH] D60401: [llvm-exegesis] When generating templates with chained instructions, also add templates for helper instructions

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
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To measure characteristics of instruction Instr, we sometimes need to
chain it together with some other instructions. But that gives us
collective characteristics of those instructions combined.

Initially, in D60000 <https://reviews.llvm.org/D60000>, i have proposed to recover the actual characteristics
of the actual target instruction by using the LLVM scheduling data of
the helper instructions. But it was pointed out that we should not depend
on a-priori data, and use measurements only.

But for that, we need to not only measure the target instruction,
but also measure the instructions that were chained to the target instruction.

I don't believe those measurements should be done by hand.
If i want to measure latency of instruction that can't be executed serially,
at most, i'm willing to run analysis mode on the *automated* measurements,
i don't really want to look what instructions llvm-exegesis has used to
serialize execution. But maybe that is just me?


Repository:
  rL LLVM

https://reviews.llvm.org/D60401

Files:
  tools/llvm-exegesis/lib/SnippetGenerator.cpp
  tools/llvm-exegesis/lib/SnippetGenerator.h
  unittests/tools/llvm-exegesis/X86/SnippetGeneratorTest.cpp

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