[glibc/users/skpgkp2/2.33/master] Use GCC builtins for roundeven functions if desired.

[Sunil Pandey <skpgkp2@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=6e6e51a1a27c0c315187569b41badc41c8f40afa

commit 6e6e51a1a27c0c315187569b41badc41c8f40afa
Author: Shen-Ta Hsieh <ibmibmibm.tw@gmail.com>
Date:   Mon May 24 09:43:12 2021 +0800

    Use GCC builtins for roundeven functions if desired.
    
    This patch is using the corresponding GCC builtin for roundevenf,
    roundeven and roundevenl if the USE_FUNCTION_BUILTIN macros are defined
    to one in math-use-builtins.h.
    
    These builtin functions is supported since GCC 10.
    
    The code of the generic implementation is not changed.
    
    Signed-off-by: Shen-Ta Hsieh <ibmibmibm.tw@gmail.com>
    Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
    (cherry picked from commit eb9066203f6e07128d42f771def4b7ad37b25dc1)

Diff:
---
 sysdeps/generic/math-use-builtins-roundeven.h | 4 ++++
 sysdeps/generic/math-use-builtins.h           | 1 +
 sysdeps/ieee754/dbl-64/s_roundeven.c          | 5 +++++
 sysdeps/ieee754/float128/float128_private.h   | 2 ++
 sysdeps/ieee754/flt-32/s_roundevenf.c         | 5 +++++
 sysdeps/ieee754/ldbl-128/s_roundevenl.c       | 5 +++++
 6 files changed, 22 insertions(+)

diff --git a/sysdeps/generic/math-use-builtins-roundeven.h b/sysdeps/generic/math-use-builtins-roundeven.h
new file mode 100644
index 0000000000..bd2e84c93f
--- /dev/null
+++ b/sysdeps/generic/math-use-builtins-roundeven.h
@@ -0,0 +1,4 @@
+#define USE_ROUNDEVEN_BUILTIN 0
+#define USE_ROUNDEVENF_BUILTIN 0
+#define USE_ROUNDEVENL_BUILTIN 0
+#define USE_ROUNDEVENF128_BUILTIN 0
diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
index cc3e9f2201..19d2d1cf3c 100644
--- a/sysdeps/generic/math-use-builtins.h
+++ b/sysdeps/generic/math-use-builtins.h
@@ -30,6 +30,7 @@
 #include <math-use-builtins-ceil.h>
 #include <math-use-builtins-trunc.h>
 #include <math-use-builtins-round.h>
+#include <math-use-builtins-roundeven.h>
 #include <math-use-builtins-copysign.h>
 #include <math-use-builtins-sqrt.h>
 #include <math-use-builtins-fma.h>
diff --git a/sysdeps/ieee754/dbl-64/s_roundeven.c b/sysdeps/ieee754/dbl-64/s_roundeven.c
index 5deff3bb8a..88c051e9fe 100644
--- a/sysdeps/ieee754/dbl-64/s_roundeven.c
+++ b/sysdeps/ieee754/dbl-64/s_roundeven.c
@@ -21,6 +21,7 @@
 #include <math_private.h>
 #include <libm-alias-double.h>
 #include <stdint.h>
+#include <math-use-builtins.h>
 
 #define BIAS 0x3ff
 #define MANT_DIG 53
@@ -29,6 +30,9 @@
 double
 __roundeven (double x)
 {
+#if USE_ROUNDEVEN_BUILTIN
+  return __builtin_roundeven (x);
+#else
   uint64_t ix, ux;
   EXTRACT_WORDS64 (ix, x);
   ux = ix & 0x7fffffffffffffffULL;
@@ -66,6 +70,7 @@ __roundeven (double x)
     ix &= 0x8000000000000000ULL;
   INSERT_WORDS64 (x, ix);
   return x;
+#endif /* ! USE_ROUNDEVEN_BUILTIN  */
 }
 #ifndef __roundeven
 libm_alias_double (__roundeven, roundeven)
diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index 979138851b..b6b6d3d5fd 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -152,6 +152,8 @@
 #define USE_TRUNCL_BUILTIN USE_TRUNCF128_BUILTIN
 #undef USE_ROUNDL_BUILTIN
 #define USE_ROUNDL_BUILTIN USE_ROUNDF128_BUILTIN
+#undef USE_ROUNDEVENL_BUILTIN
+#define USE_ROUNDEVENL_BUILTIN USE_ROUNDEVENF128_BUILTIN
 #undef USE_COPYSIGNL_BUILTIN
 #define USE_COPYSIGNL_BUILTIN USE_COPYSIGNF128_BUILTIN
 #undef USE_FMAL_BUILTIN
diff --git a/sysdeps/ieee754/flt-32/s_roundevenf.c b/sysdeps/ieee754/flt-32/s_roundevenf.c
index 2cc0d7b001..4f568579d8 100644
--- a/sysdeps/ieee754/flt-32/s_roundevenf.c
+++ b/sysdeps/ieee754/flt-32/s_roundevenf.c
@@ -21,6 +21,7 @@
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-float.h>
+#include <math-use-builtins.h>
 #include <stdint.h>
 
 #define BIAS 0x7f
@@ -30,6 +31,9 @@
 float
 __roundevenf (float x)
 {
+#if USE_ROUNDEVENF_BUILTIN
+  return __builtin_roundevenf (x);
+#else
   uint32_t ix, ux;
   GET_FLOAT_WORD (ix, x);
   ux = ix & 0x7fffffff;
@@ -67,6 +71,7 @@ __roundevenf (float x)
     ix &= 0x80000000;
   SET_FLOAT_WORD (x, ix);
   return x;
+#endif /* ! USE_ROUNDEVENF_BUILTIN  */
 }
 #ifndef __roundevenf
 libm_alias_float (__roundeven, roundeven)
diff --git a/sysdeps/ieee754/ldbl-128/s_roundevenl.c b/sysdeps/ieee754/ldbl-128/s_roundevenl.c
index 7c9c11fad2..afbf13d4f2 100644
--- a/sysdeps/ieee754/ldbl-128/s_roundevenl.c
+++ b/sysdeps/ieee754/ldbl-128/s_roundevenl.c
@@ -21,6 +21,7 @@
 #include <math.h>
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 #include <stdint.h>
 
 #define BIAS 0x3fff
@@ -30,6 +31,9 @@
 _Float128
 __roundevenl (_Float128 x)
 {
+#if USE_ROUNDEVENL_BUILTIN
+  return __builtin_roundevenl (x);
+#else
   uint64_t hx, lx, uhx;
   GET_LDOUBLE_WORDS64 (hx, lx, x);
   uhx = hx & 0x7fffffffffffffffULL;
@@ -101,5 +105,6 @@ __roundevenl (_Float128 x)
     }
   SET_LDOUBLE_WORDS64 (x, hx, lx);
   return x;
+#endif /* ! USE_ROUNDEVENL_BUILTIN  */
 }
 libm_alias_ldouble (__roundeven, roundeven)