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Bug 49189 - update_llc_test_checks.py doesn't report when a common prefix has been lost
Summary: update_llc_test_checks.py doesn't report when a common prefix has been lost
Status: NEW
Alias: None
Product: tools
Classification: Unclassified
Component: support scripts (show other bugs)
Version: trunk
Hardware: PC Windows NT
: P enhancement
Assignee: Unassigned LLVM Bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2021-02-15 04:10 PST by Simon Pilgrim
Modified: 2021-02-15 10:08 PST (History)
6 users (show)

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Description Simon Pilgrim 2021-02-15 04:10:26 PST 
https://reviews.llvm.org/rGf32dc6bb42fd24517289fd1e3418994daa4fec20

; RUN: llc < %s -mtriple=x86_64-- -mattr=+avx2 | FileCheck %s --check-prefixes=AVX,AVX2
; RUN: llc < %s -mtriple=x86_64-- -mattr=+avx2,+fast-variable-shuffle | FileCheck %s --check-prefixes=AVX,AVX2

update_llc_test_checks.py didn't report that two AVX2 runs had conflicting checks for all their common prefixes, which meant we lost ALL test coverage.
Comment 1 Mircea Trofin 2021-02-15 08:15:23 PST 
FWIW, I don't believe update_llc_test_checks.py ever reported (at least, not consistently) that a given RUN line ends up having no used prefix.
Comment 2 Simon Pilgrim 2021-02-15 09:48:13 PST 
(In reply to Mircea Trofin from comment #1)
> FWIW, I don't believe update_llc_test_checks.py ever reported (at least, not
> consistently) that a given RUN line ends up having no used prefix.

Prior to D93078, we would warn when we found a mismatch under the last remaining common prefix:

  warn('Found conflicting asm under the same prefix: %r!' % (prefix,))
Comment 3 Mircea Trofin 2021-02-15 10:08:26 PST 
Which, as D93078 details, wasn't actually working; in this case, in particular, it wasn't (try sync-ing before that patch and running update_llc_test_checks)