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This patch implements the following set of changes:
1. If a component flag of -ffast-math (or -funsafe-math-optimizations)
is explicitly set (or reset) on the command line, this should override
any implicit change due to -f(no-)fast-math, no matter in which order
the flags come on the command line. This change affects all flags.
2. Any component flag modified from its default by -ffast-math should
be reset to the default by -fno-fast-math. This was previously
not done for the following flags:
-fcx-limited-range
-fexcess-precision=
3. Once -ffinite-math-only is true, the -f(no-)signaling-nans flag has
no meaning (if we have no NaNs at all, it does not matter whether
there is a difference between quiet and signaling NaNs). Therefore,
it does not make sense for -ffast-math to imply -fno-signaling-nans.
(This is also a documentation change.)
4. -ffast-math is documented to imply -fno-rounding-math, however the
latter setting is the default anyway; therefore it does not make
sense to try to modify it from its default setting.
5. The __FAST_MATH__ preprocessor macro should be defined if and only
if all the component flags of -ffast-math are set to the value that
is documented as the effect of -ffast-math. The following flags
were currently *not* so tested:
-fcx-limited-range
-fassociative-math
-freciprocal-math
-frounding-math
(Note that we should still *test* for -fno-rounding-math here even
though it is not set as to 4. -ffast-math -frounding-math should
not set the __FAST_MATH__ macro.)
This is also a documentation change.
2020-11-24 Ulrich Weigand <uweigand@de.ibm.com>
gcc/
* doc/invoke.texi (-ffast-math): Remove mention of -fno-signaling-nans.
Clarify conditions when __FAST_MATH__ preprocessor macro is defined.
* opts.c (common_handle_option): Pass OPTS_SET to set_fast_math_flags
and set_unsafe_math_optimizations_flags.
(set_fast_math_flags): Add OPTS_SET argument, and use it to avoid
setting flags already explicitly set on the command line. In the !set
case, also reset x_flag_cx_limited_range and x_flag_excess_precision.
Never reset x_flag_signaling_nans or x_flag_rounding_math.
(set_unsafe_math_optimizations_flags): Add OPTS_SET argument, and use
it to avoid setting flags already explicitly set on the command line.
(fast_math_flags_set_p): Also test x_flag_cx_limited_range,
x_flag_associative_math, x_flag_reciprocal_math, and
x_flag_rounding_math.
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