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