https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84616
Bug ID: 84616
Summary: funsafe-math-optimizations leads to incorrect results
for 4x4 matrix inversion
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: michael at moekadu dot de
Target Milestone: ---
Created attachment 43530
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43530&action=edit
Example code for inversion of 4x4 identity matrix
Trying to do a matrix inversion from the Eigen3-library leads wrong results
when compiling with the -funsafe-math-optimizations -O1.
When inverting the identity matrix I would expect as result:
1 0 0 0
0 1 0 0
0 0 1 0
0 0 0 1
----
Instead I get the result
1 0 0 0
0 -1 0 0
0 0 1 0
0 0 0 -1
----
Compiler version: gcc7.3
CPU: Intel(R) Xeon(R) CPU E3-1276 v3 @ 3.60GHz
Eigen library version: 3.3.4
