libgfortran: Provide some further math library fallbacks [PR94694]

The following patch provides some further math library fallbacks.
fmaf can be implemented using fma if available, fma and fmal can use
x * y + z as fallback, it is not perfect, but e.g. glibc on various arches
has been using that as fallback for many years,
and copysign/copysignl/fabs/fabsl can be implemented using corresponding
__builtin_* if we make sure that gcc expands it inline instead of using
a library call (these days it is expanded inline on most targets).

2020-04-22  Jakub Jelinek  <jakub@redhat.com>

	PR libfortran/94694
	PR libfortran/94586
	* configure.ac: Add math func checks for fmaf, fma and fmal.  Add
	HAVE_INLINE_BUILTIN_COPYSIGN check.
	* c99_protos.h (copysign, fmaf, fma, fmal): Provide fallback
	prototypes.
	(HAVE_COPYSIGN, HAVE_FMAF, HAVE_FMA, HAVE_FMAL): Define if not
	defined and fallback version is provided.
	* intrinsics/c99_functions.c (copysign, fmaf, fma, fmal): Provide
	fallback implementations if possible
	* configure: Regenerated.
	* config.h.in: Regenerated.

	* math.m4 (GCC_CHECK_MATH_INLINE_BUILTIN_FALLBACK1,
	GCC_CHECK_MATH_INLINE_BUILTIN_FALLBACK2): New.

1 files changed, 77 insertions, 0 deletions

diff --git a/libgfortran/intrinsics/c99_functions.c b/libgfortran/intrinsics/c99_functions.c
index 3ec5aeb..b75d177 100644
--- a/libgfortran/intrinsics/c99_functions.c
+++ b/libgfortran/intrinsics/c99_functions.c
@@ -229,6 +229,17 @@ ceilf (float x)
 }
 #endif
 
+#if !defined(HAVE_COPYSIGN) && defined(HAVE_INLINE_BUILTIN_COPYSIGN)
+#define HAVE_COPYSIGN 1
+double copysign (double x, double y);
+
+double
+copysign (double x, double y)
+{
+  return __builtin_copysign (x, y);
+}
+#endif
+
 #ifndef HAVE_COPYSIGNF
 #define HAVE_COPYSIGNF 1
 float copysignf (float x, float y);
@@ -240,6 +251,17 @@ copysignf (float x, float y)
 }
 #endif
 
+#if !defined(HAVE_COPYSIGNL) && defined(HAVE_INLINE_BUILTIN_COPYSIGNL)
+#define HAVE_COPYSIGNL 1
+long double copysignl (long double x, long double y);
+
+long double
+copysignl (long double x, long double y)
+{
+  return __builtin_copysignl (x, y);
+}
+#endif
+
 #ifndef HAVE_COSF
 #define HAVE_COSF 1
 float cosf (float x);
@@ -273,6 +295,17 @@ expf (float x)
 }
 #endif
 
+#if !defined(HAVE_FABS) && defined(HAVE_INLINE_BUILTIN_FABS)
+#define HAVE_FABS 1
+double fabs (double x);
+
+double
+fabs (double x)
+{
+  return __builtin_fabs (x);
+}
+#endif
+
 #ifndef HAVE_FABSF
 #define HAVE_FABSF 1
 float fabsf (float x);
@@ -284,6 +317,17 @@ fabsf (float x)
 }
 #endif
 
+#if !defined(HAVE_FABSL) && defined(HAVE_INLINE_BUILTIN_FABSL)
+#define HAVE_FABSL 1
+long double fabsl (long double x);
+
+long double
+fabsl (long double x)
+{
+  return __builtin_fabsl (x);
+}
+#endif
+
 #ifndef HAVE_FLOORF
 #define HAVE_FLOORF 1
 float floorf (float x);
@@ -2112,3 +2156,36 @@ lgammaf (float x)
   return (float) lgamma ((double) x);
 }
 #endif
+
+#ifndef HAVE_FMA
+#define HAVE_FMA 1
+double fma (double, double, double);
+
+double
+fma (double x, double y, double z)
+{
+  return x * y + z;
+}
+#endif
+
+#ifndef HAVE_FMAF
+#define HAVE_FMAF 1
+float fmaf (float, float, float);
+
+float
+fmaf (float x, float y, float z)
+{
+  return fma (x, y, z);
+}
+#endif
+
+#ifndef HAVE_FMAL
+#define HAVE_FMAL 1
+long double fmal (long double, long double, long double);
+
+long double
+fmal (long double x, long double y, long double z)
+{
+  return x * y + z;
+}
+#endif