https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83206
Bug ID: 83206
Summary: -mfpu=auto does not work on ARM
(armv7l-unknown-linux-gnueabihf)
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: driver
Assignee: unassigned at gcc dot gnu.org
Reporter: andrewm.roberts at sky dot com
Target Milestone: ---
On ARM an option to -mfpu is auto, this is given when you do:
/usr/local/gcc/bin/gcc -mcpu=native -Q --help=target
...
Known ARM FPUs (for use with the -mfpu= option):
auto crypto-neon-fp-armv8 fp-armv8 fpv4-sp-d16 fpv5-d16 fpv5-sp-d16 neon
neon-fp-armv8 neon-fp16 neon-vfpv3 neon-vfpv4 vfp vfp3 vfpv2 vfpv3
vfpv3-d16
vfpv3-d16-fp16 vfpv3-fp16 vfpv3xd vfpv3xd-fp16 vfpv4 vfpv4-d16
If you try:
/usr/local/gcc/bin/gcc -mcpu=native -mfpu=auto -Q --help=target
You get:
-mfpu= auto
But if you try to use it:
gcc -march=native -mcpu=native -mtune=native -mfpu=auto -Ofast -o matrix
matrix.c
You get:
cc1: error: -mfloat-abi=hard: selected processor lacks an FPU
which isn't true as:
gcc -march=native -mcpu=native -mtune=native -mfpu=neon -Ofast -o matrix
matrix.c
works
as does
-mfpu=vfpv3-d16
etc
This is true on:
armv7l and armv6l at least, tested on:
ODROID-XU3: (ARM big/little Cortex-A15/A7)
Raspbery Pi B: (ARM ARM1176)
Raspberry Pi 2B v1: (ARM Cortex-A7)
Raspberry Pi 3B: (ARM Cortex-A53)
