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Bug 34635 - r312791 causes SLP vectorizer to miscompile signed int min reductions
Summary: r312791 causes SLP vectorizer to miscompile signed int min reductions
Status: RESOLVED FIXED
Alias: None
Product: new-bugs
Classification: Unclassified
Component: new bugs (show other bugs)
Version: trunk
Hardware: PC All
: P enhancement
Assignee: Unassigned LLVM Bugs
URL:
Keywords:
Depends on:
Blocks:
 
Reported: 2017-09-15 14:58 PDT by Chandler Carruth
Modified: 2018-12-15 05:59 PST (History)
3 users (show)

See Also:
Fixed By Commit(s): rL347759

Attachments
test case (6.72 KB, text/plain)
2017-09-15 14:58 PDT, Chandler Carruth 		Details
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Description Chandler Carruth 2017-09-15 14:58:17 PDT 
Created attachment 19165 [details]
test case

Test case attached. To reproduce:

% llc < slp_test.ll | clang -x assembler - -o slp_test.good && ./slp_test.good
minidx = 5

% opt < slp_test.ll -passes=slp-vectorizer | llc | clang -x assembler - -o slp_test.bad && ./slp_test.bad
minidx = 6
<Abort>

I'm going to revert for now.
Comment 1 Chandler Carruth 2017-09-15 15:24:42 PDT 
Reverted in r313409 while the miscompile is investigated. I did look somewhat carefully and for the life of me I can't see why this is miscompiling. =/
Comment 2 Simon Pilgrim 2018-12-15 05:21:35 PST 
I'm guessing but this might have been fixed by rL347759