https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110888
Bug ID: 110888
Summary: Missing optimization for trivial MATMUL cases,
requires -fno-signed-zeros
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: rimvydas.jas at gmail dot com
Target Milestone: ---
$ cat foo.f90
subroutine foo(x,y,z)
implicit none
real(kind=selected_real_kind(9,99)) :: x(1), y(1,1), z(1)
z = matmul(x,y)
end subroutine
$ gfortran -c -S -Wall -Wextra -O2 -fdump-tree-optimized foo.f90
The do loop get reduced in matmul intrinsic implementation, however redundant
accumulator store is not optimized out during PRE if
-ffast-math(-fno-signed-zeros) is not used:
<bb 2> [local count: 536870912]:
__builtin_memset (z_11(D), 0, 8);
- _18 = (*z_11(D))[0];
_19 = (*x_13(D))[0];
_20 = (*y_14(D))[0];
_21 = _19 * _20;
- _22 = _18 + _21;
+ _22 = _21 + 0.0;
(*z_11(D))[0] = _22;
return;
Not sure if it is possible to mark accumulator expr as artificial so that
optimizers could ignore side effects by default, but luckily it is easily
avoidable in frontend itself.
