[Patch] Turn -fexcess-precision=fast on when in -ffast-math

	* common.opt (excess_precision): Tag as SetByCombined.
	* opts.c (set_fast_math_flags): Also set
	flag_excess_precision_cmdline.
	(fast_math_flags_set_p): Also check flag_excess_precision_cmdline.
	* doc/invoke.texi (-fexcess-precision): Drop text saying the
	option has no effect under -ffast-math, make it clear that
	-ffast-math will cause -fexcess-precision=fast by default even for
	standards compliant modes.
	(-ffast-math): Document that this sets -fexcess-precision=fast.

From-SVN: r243824

4 files changed, 25 insertions, 6 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 6d22e94..156408f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,15 @@
+2016-12-20  James Greenhalgh  <james.greenhalghj@arm.com>
+
+	* common.opt (excess_precision): Tag as SetByCombined.
+	* opts.c (set_fast_math_flags): Also set
+	flag_excess_precision_cmdline.
+	(fast_math_flags_set_p): Also check flag_excess_precision_cmdline.
+	* doc/invoke.texi (-fexcess-precision): Drop text saying the
+	option has no effect under -ffast-math, make it clear that
+	-ffast-math will cause -fexcess-precision=fast by default even for
+	standards compliant modes.
+	(-ffast-math): Document that this sets -fexcess-precision=fast.
+
 2016-12-20  Richard Biener  <rguenther@suse.de>
 
 	* passes.c (execute_one_pass): Handle going out of SSA w/o
diff --git a/gcc/common.opt b/gcc/common.opt
index de06844..6ebaf9c 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -1317,7 +1317,7 @@ Common Report Var(flag_expensive_optimizations) Optimization
 Perform a number of minor, expensive optimizations.
 
 fexcess-precision=
-Common Joined RejectNegative Enum(excess_precision) Var(flag_excess_precision_cmdline) Init(EXCESS_PRECISION_DEFAULT)
+Common Joined RejectNegative Enum(excess_precision) Var(flag_excess_precision_cmdline) Init(EXCESS_PRECISION_DEFAULT) SetByCombined
 -fexcess-precision=[fast|standard]	Specify handling of excess floating-point precision.
 
 Enum
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index b729964..5c92fe6 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -9109,12 +9109,12 @@ both casts and assignments cause values to be rounded to their
 semantic types (whereas @option{-ffloat-store} only affects
 assignments).  This option is enabled by default for C if a strict
 conformance option such as @option{-std=c99} is used.
+@option{-ffast-math} enables @option{-fexcess-precision=fast} by default
+regardless of whether a strict conformance option is used.
 
 @opindex mfpmath
 @option{-fexcess-precision=standard} is not implemented for languages
-other than C, and has no effect if
-@option{-funsafe-math-optimizations} or @option{-ffast-math} is
-specified.  On the x86, it also has no effect if @option{-mfpmath=sse}
+other than C.  On the x86, it has no effect if @option{-mfpmath=sse}
 or @option{-mfpmath=sse+387} is specified; in the former case, IEEE
 semantics apply without excess precision, and in the latter, rounding
 is unpredictable.
@@ -9123,7 +9123,8 @@ is unpredictable.
 @opindex ffast-math
 Sets the options @option{-fno-math-errno}, @option{-funsafe-math-optimizations},
 @option{-ffinite-math-only}, @option{-fno-rounding-math},
-@option{-fno-signaling-nans} and @option{-fcx-limited-range}.
+@option{-fno-signaling-nans}, @option{-fcx-limited-range} and
+@option{-fexcess-precision=fast}.
 
 This option causes the preprocessor macro @code{__FAST_MATH__} to be defined.
 
diff --git a/gcc/opts.c b/gcc/opts.c
index 890da03..5844190 100644
--- a/gcc/opts.c
+++ b/gcc/opts.c
@@ -2342,6 +2342,10 @@ set_fast_math_flags (struct gcc_options *opts, int set)
     opts->x_flag_errno_math = !set;
   if (set)
     {
+      if (opts->frontend_set_flag_excess_precision_cmdline
+	  == EXCESS_PRECISION_DEFAULT)
+	opts->x_flag_excess_precision_cmdline
+	  = set ? EXCESS_PRECISION_FAST : EXCESS_PRECISION_DEFAULT;
       if (!opts->frontend_set_flag_signaling_nans)
 	opts->x_flag_signaling_nans = 0;
       if (!opts->frontend_set_flag_rounding_math)
@@ -2374,7 +2378,9 @@ fast_math_flags_set_p (const struct gcc_options *opts)
 	  && opts->x_flag_unsafe_math_optimizations
 	  && opts->x_flag_finite_math_only
 	  && !opts->x_flag_signed_zeros
-	  && !opts->x_flag_errno_math);
+	  && !opts->x_flag_errno_math
+	  && opts->x_flag_excess_precision_cmdline
+	     == EXCESS_PRECISION_FAST);
 }
 
 /* Return true iff flags are set as if -ffast-math but using the flags stored