Hello Sandra,
On 15/01/2021 20:12, Sandra Loosemore wrote:
The following instructions supported by this component are not enabled
by this option:
* -mcustom-fmins
* -mcustom-fmaxs
* -mcustom-round
The reason is that these instructions are only in effect in combination
with other options. If they are not set, then a build error occurs in
libatomic since -Werror is used for building this library:
cc1: error: switch '-mcustom-fmins' has no effect unless
'-ffinite-math-only' is specified [-Werror]
cc1: error: switch '-mcustom-fmaxs' has no effect unless
'-ffinite-math-only' is specified [-Werror]
cc1: error: switch '-mcustom-round' has no effect unless
'-fno-math-errno' is specified [-Werror]
Seems like it would be better to have a separate switch to disable
these warnings, or perhaps remove them entirely, as I'm sure there are
other custom instructions that are not used unless -ffinite-math-only,
-fno-math-errno, or -ffast-math are also specified (e.g., I see an
issue in our internal tracker about fsqrts) and we don't consistently
warn about those. So I think the warnings are of dubious value.
Maybe the existing -Wdisabled-optimization flag could be used here to
control the warnings we're already checking for?
thanks for having a look at it. It would be good to control the warning
via an option not enabled by -Wall or remove the warnings. The
-Wdisabled-optimization not used in gcc/config/*:
grep -r 'warning (OPT_Wdisabled' gcc/
gcc/tree-ssa-loop-prefetch.c: warning (OPT_Wdisabled_optimization,
gcc/gcse.c: warning (OPT_Wdisabled_optimization,
gcc/gcse.c: warning (OPT_Wdisabled_optimization,
The warning description doesn't really fit from my point of view.
Maybe use -Wextra which is already used by avr (not really a prime target):
grep -r 'warning (OPT_Wextra' gcc/config
gcc/config/avr/avr.c: warning (OPT_Wextra, "rounding to %d bits
has no effect for "
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