[glibc] Use GCC builtins for round functions if desired.

[Stefan Liebler <stli@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=f82996f8159981619ac7ed8a4c1838c2ad72ab61

commit f82996f8159981619ac7ed8a4c1838c2ad72ab61
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Wed Dec 11 15:09:24 2019 +0100

    Use GCC builtins for round functions if desired.
    
    This patch is using the corresponding GCC builtin for roundf, round,
    roundl and roundf128 if the USE_FUNCTION_BUILTIN macros are defined to one
    in math-use-builtins.h.
    
    This is the case for s390 if build with at least --march=z196 --mzarch.
    Otherwise the generic implementation is used.  The code of the generic
    implementation is not changed.
    
    Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>

Diff:
---
 sysdeps/generic/math-use-builtins.h         |  5 +++++
 sysdeps/ieee754/dbl-64/s_round.c            |  6 ++++++
 sysdeps/ieee754/float128/float128_private.h |  3 +++
 sysdeps/ieee754/flt-32/s_roundf.c           |  6 ++++++
 sysdeps/ieee754/ldbl-128/s_roundl.c         |  6 ++++++
 sysdeps/s390/fpu/math-use-builtins.h        | 11 +++++++++++
 6 files changed, 37 insertions(+)

diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
index ab379f4..34ca438 100644
--- a/sysdeps/generic/math-use-builtins.h
+++ b/sysdeps/generic/math-use-builtins.h
@@ -46,4 +46,9 @@
 #define USE_TRUNCL_BUILTIN 0
 #define USE_TRUNCF128_BUILTIN 0
 
+#define USE_ROUND_BUILTIN 0
+#define USE_ROUNDF_BUILTIN 0
+#define USE_ROUNDL_BUILTIN 0
+#define USE_ROUNDF128_BUILTIN 0
+
 #endif /* math-use-builtins.h */
diff --git a/sysdeps/ieee754/dbl-64/s_round.c b/sysdeps/ieee754/dbl-64/s_round.c
index 8f4b7cf..7eb1ecb 100644
--- a/sysdeps/ieee754/dbl-64/s_round.c
+++ b/sysdeps/ieee754/dbl-64/s_round.c
@@ -23,11 +23,16 @@
 #include <math_private.h>
 #include <libm-alias-double.h>
 #include <stdint.h>
+#include <math-use-builtins.h>
 
 
 double
 __round (double x)
 {
+#if USE_ROUND_BUILTIN
+  return __builtin_round (x);
+#else
+  /* Use generic implementation.  */
   int64_t i0, j0;
 
   EXTRACT_WORDS64 (i0, x);
@@ -62,5 +67,6 @@ __round (double x)
 
   INSERT_WORDS64 (x, i0);
   return x;
+#endif /* ! USE_ROUND_BUILTIN  */
 }
 libm_alias_double (__round, round)
diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index 9cd3a63..a6c76ce 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -150,6 +150,8 @@
 #define USE_CEILL_BUILTIN USE_CEILF128_BUILTIN
 #undef USE_TRUNCL_BUILTIN
 #define USE_TRUNCL_BUILTIN USE_TRUNCF128_BUILTIN
+#undef USE_ROUNDL_BUILTIN
+#define USE_ROUNDL_BUILTIN USE_ROUNDF128_BUILTIN
 
 /* IEEE function renames.  */
 #define __ieee754_acoshl __ieee754_acoshf128
@@ -358,6 +360,7 @@
 #define __builtin_floorl __builtin_floorf128
 #define __builtin_ceill __builtin_ceilf128
 #define __builtin_truncl __builtin_truncf128
+#define __builtin_roundl __builtin_roundf128
 
 /* Get the constant suffix from bits/floatn-compat.h.  */
 #define L(x) __f128 (x)
diff --git a/sysdeps/ieee754/flt-32/s_roundf.c b/sysdeps/ieee754/flt-32/s_roundf.c
index cddab7b..5d91239 100644
--- a/sysdeps/ieee754/flt-32/s_roundf.c
+++ b/sysdeps/ieee754/flt-32/s_roundf.c
@@ -22,11 +22,16 @@
 
 #include <math_private.h>
 #include <libm-alias-float.h>
+#include <math-use-builtins.h>
 
 
 float
 __roundf (float x)
 {
+#if USE_ROUNDF_BUILTIN
+  return __builtin_roundf (x);
+#else
+  /* Use generic implementation.  */
   int32_t i0, j0;
 
   GET_FLOAT_WORD (i0, x);
@@ -61,5 +66,6 @@ __roundf (float x)
 
   SET_FLOAT_WORD (x, i0);
   return x;
+#endif /* ! USE_ROUNDF_BUILTIN  */
 }
 libm_alias_float (__round, round)
diff --git a/sysdeps/ieee754/ldbl-128/s_roundl.c b/sysdeps/ieee754/ldbl-128/s_roundl.c
index d41c9a0..8c7ae82 100644
--- a/sysdeps/ieee754/ldbl-128/s_roundl.c
+++ b/sysdeps/ieee754/ldbl-128/s_roundl.c
@@ -23,11 +23,16 @@
 
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 
 
 _Float128
 __roundl (_Float128 x)
 {
+#if USE_ROUNDL_BUILTIN
+  return __builtin_roundl (x);
+#else
+  /* Use generic implementation.  */
   int32_t j0;
   uint64_t i1, i0;
 
@@ -78,5 +83,6 @@ __roundl (_Float128 x)
 
   SET_LDOUBLE_WORDS64 (x, i0, i1);
   return x;
+#endif /* ! USE_ROUNDL_BUILTIN  */
 }
 libm_alias_ldouble (__round, round)
diff --git a/sysdeps/s390/fpu/math-use-builtins.h b/sysdeps/s390/fpu/math-use-builtins.h
index a39715c..51cb9f9 100644
--- a/sysdeps/s390/fpu/math-use-builtins.h
+++ b/sysdeps/s390/fpu/math-use-builtins.h
@@ -46,18 +46,24 @@
 # define USE_TRUNCF_BUILTIN 1
 # define USE_TRUNCL_BUILTIN 1
 
+# define USE_ROUND_BUILTIN 1
+# define USE_ROUNDF_BUILTIN 1
+# define USE_ROUNDL_BUILTIN 1
+
 # if __GNUC_PREREQ (8, 0)
 #  define USE_NEARBYINTF128_BUILTIN 1
 #  define USE_RINTF128_BUILTIN 1
 #  define USE_FLOORF128_BUILTIN 1
 #  define USE_CEILF128_BUILTIN 1
 #  define USE_TRUNCF128_BUILTIN 1
+#  define USE_ROUNDF128_BUILTIN 1
 # else
 #  define USE_NEARBYINTF128_BUILTIN 0
 #  define USE_RINTF128_BUILTIN 0
 #  define USE_FLOORF128_BUILTIN 0
 #  define USE_CEILF128_BUILTIN 0
 #  define USE_TRUNCF128_BUILTIN 0
+#  define USE_ROUNDF128_BUILTIN 0
 # endif
 
 #else
@@ -88,6 +94,11 @@
 # define USE_TRUNCL_BUILTIN 0
 # define USE_TRUNCF128_BUILTIN 0
 
+# define USE_ROUND_BUILTIN 0
+# define USE_ROUNDF_BUILTIN 0
+# define USE_ROUNDL_BUILTIN 0
+# define USE_ROUNDF128_BUILTIN 0
+
 #endif /* ! HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT  */
 
 #endif /* math-use-builtins.h */