https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71615
Bug ID: 71615
Summary: wrong float point result with {-Ofast, -march=native,
and valgrind}
Product: gcc
Version: 5.3.1
Status: UNCONFIRMED
Severity: major
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: wangmianzhi1 at linuxmail dot org
Target Milestone: ---
Created attachment 38742
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=38742&action=edit
reduced test
Problem:
float point calculation gives wrong result
Hardware:
AMD A4-5000 CPU
Software:
Ubuntu 16.04 x86_64
gcc and valgrind from apt
Steps to Repeat the Bug:
1. compile the attached REDUCED test code with
$ gfortran -Wall -Ofast -march=native test.f90 -o test
2. execute the program via valgrind
$ valgriand ./test
Result:
The calculation gives
0.0000000000000000 -2.6901205975860183 0.95110109754591643
While the correct result should be
0.0000000000000000 -0.94280905929685954 0.33333328322831940
Note:
Would give the correct result WITHOUT ANY of {-Ofast, -march=native, or
valgrind}.
