https://llvm.org/bugs/show_bug.cgi?id=26110
Bug ID: 26110
Summary: clang c compiler produces wrong result for the
attached c code with -O2 optimzation
Product: clang
Version: 3.7
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: release blocker
Priority: P
Component: LLVM Codegen
Assignee: unassignedclangb...@nondot.org
Reporter: garunsriniva...@gmail.com
CC: llvm-bugs@lists.llvm.org
Classification: Unclassified
Created attachment 15602
--> https://llvm.org/bugs/attachment.cgi?id=15602&action=edit
C file that reproduces the problem
A bug in the llvm auto vectoizer produces wrong results for the attached c
file. Turning off auto vectorizer produces the right results, but makes the
bigger test cases run much slower.
Compile the attached c file with xcode 7.0x or later with (clang-700.1.81)
(based on LLVM 3.7.0svn) with the following command:
bad result:
===============================
% clang -O2 bug.c -Wall -o bad
% ./bad
dbg = 10 10 10 10 10 10 10 10
good result:
===============================
% clang -O2 -fno-vectorize bug.c -Wall -o bad
%./bad
dbg = 15 15 15 15 15 15 15 15
gcc 4.7
% gcc -O2 bug.c -Wall -o bad
% ./bad
dbg = 15 15 15 15 15 15 15 15
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