https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88713
Bug ID: 88713
Summary: _gfortran_internal_pack@PLT prevents vectorization
Product: gcc
Version: 8.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: fortran
Assignee: unassigned at gcc dot gnu.org
Reporter: elrodc at gmail dot com
Target Milestone: ---
Created attachment 45350
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=45350&action=edit
Fortran version of vectorization test.
I am attaching Fortran and C++ translations of a simple working example.
The C++ version is vectorized, while the Fortran version is not.
The code consists of two functions. One simply runs a for loop, calling the
other function.
The function is vectorizable across loop iterations. g++ does this
succcesfully.
However, gfortran does not, because it repacks data with
call _gfortran_internal_pack@PLT
so that it can no longer be vectorized across iterations.
I compiled with:
gfortran -Ofast -march=skylake-avx512 -mprefer-vector-width=512
-fno-semantic-interposition -shared -fPIC -S vectorization_test.cpp -o
gfortvectorization_test.s
g++ -Ofast -march=skylake-avx512 -mprefer-vector-width=512 -shared -fPIC -S
vectorization_test.cpp -o gppvectorization_test.s
LLVM (via flang and clang) successfully vectorizes both versions.
