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

[Stefan Liebler <stli@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=1ac9c1cf87216bf9f8ac4f7c9754d025d9f2c4ae

commit 1ac9c1cf87216bf9f8ac4f7c9754d025d9f2c4ae
Author: Stefan Liebler <stli@linux.ibm.com>
Date:   Wed Dec 11 15:09:22 2019 +0100

    Use GCC builtins for trunc functions if desired.
    
    This patch is using the corresponding GCC builtin for truncf, trunc,
    truncl and truncf128 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_trunc.c            |  6 ++++++
 sysdeps/ieee754/float128/float128_private.h |  3 +++
 sysdeps/ieee754/flt-32/s_truncf.c           |  6 ++++++
 sysdeps/ieee754/ldbl-128/s_truncl.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 076ec66..ab379f4 100644
--- a/sysdeps/generic/math-use-builtins.h
+++ b/sysdeps/generic/math-use-builtins.h
@@ -41,4 +41,9 @@
 #define USE_CEILL_BUILTIN 0
 #define USE_CEILF128_BUILTIN 0
 
+#define USE_TRUNC_BUILTIN 0
+#define USE_TRUNCF_BUILTIN 0
+#define USE_TRUNCL_BUILTIN 0
+#define USE_TRUNCF128_BUILTIN 0
+
 #endif /* math-use-builtins.h */
diff --git a/sysdeps/ieee754/dbl-64/s_trunc.c b/sysdeps/ieee754/dbl-64/s_trunc.c
index 0de68ce..c3129fe 100644
--- a/sysdeps/ieee754/dbl-64/s_trunc.c
+++ b/sysdeps/ieee754/dbl-64/s_trunc.c
@@ -22,11 +22,16 @@
 
 #include <math_private.h>
 #include <libm-alias-double.h>
+#include <math-use-builtins.h>
 
 
 double
 __trunc (double x)
 {
+#if USE_TRUNC_BUILTIN
+  return __builtin_trunc (x);
+#else
+  /* Use generic implementation.  */
   int64_t i0, j0;
   int64_t sx;
 
@@ -49,6 +54,7 @@ __trunc (double x)
     }
 
   return x;
+#endif /* ! USE_TRUNC_BUILTIN  */
 }
 #ifndef __trunc
 libm_alias_double (__trunc, trunc)
diff --git a/sysdeps/ieee754/float128/float128_private.h b/sysdeps/ieee754/float128/float128_private.h
index 01881b5..9cd3a63 100644
--- a/sysdeps/ieee754/float128/float128_private.h
+++ b/sysdeps/ieee754/float128/float128_private.h
@@ -148,6 +148,8 @@
 #define USE_FLOORL_BUILTIN USE_FLOORF128_BUILTIN
 #undef USE_CEILL_BUILTIN
 #define USE_CEILL_BUILTIN USE_CEILF128_BUILTIN
+#undef USE_TRUNCL_BUILTIN
+#define USE_TRUNCL_BUILTIN USE_TRUNCF128_BUILTIN
 
 /* IEEE function renames.  */
 #define __ieee754_acoshl __ieee754_acoshf128
@@ -355,6 +357,7 @@
 #define __builtin_rintl __builtin_rintf128
 #define __builtin_floorl __builtin_floorf128
 #define __builtin_ceill __builtin_ceilf128
+#define __builtin_truncl __builtin_truncf128
 
 /* Get the constant suffix from bits/floatn-compat.h.  */
 #define L(x) __f128 (x)
diff --git a/sysdeps/ieee754/flt-32/s_truncf.c b/sysdeps/ieee754/flt-32/s_truncf.c
index e587706..2746388 100644
--- a/sysdeps/ieee754/flt-32/s_truncf.c
+++ b/sysdeps/ieee754/flt-32/s_truncf.c
@@ -22,11 +22,16 @@
 
 #include <math_private.h>
 #include <libm-alias-float.h>
+#include <math-use-builtins.h>
 
 
 float
 __truncf (float x)
 {
+#if USE_TRUNCF_BUILTIN
+  return __builtin_truncf (x);
+#else
+  /* Use generic implementation.  */
   int32_t i0, j0;
   int sx;
 
@@ -49,6 +54,7 @@ __truncf (float x)
     }
 
   return x;
+#endif /* ! USE_TRUNCF_BUILTIN  */
 }
 #ifndef __truncf
 libm_alias_float (__trunc, trunc)
diff --git a/sysdeps/ieee754/ldbl-128/s_truncl.c b/sysdeps/ieee754/ldbl-128/s_truncl.c
index de4dd34..d11ab93 100644
--- a/sysdeps/ieee754/ldbl-128/s_truncl.c
+++ b/sysdeps/ieee754/ldbl-128/s_truncl.c
@@ -23,11 +23,16 @@
 
 #include <math_private.h>
 #include <libm-alias-ldouble.h>
+#include <math-use-builtins.h>
 
 
 _Float128
 __truncl (_Float128 x)
 {
+#if USE_TRUNCL_BUILTIN
+  return __builtin_truncl (x);
+#else
+  /* Use generic implementation.  */
   int32_t j0;
   uint64_t i0, i1, sx;
 
@@ -54,5 +59,6 @@ __truncl (_Float128 x)
     }
 
   return x;
+#endif /* ! USE_TRUNCL_BUILTIN  */
 }
 libm_alias_ldouble (__trunc, trunc)
diff --git a/sysdeps/s390/fpu/math-use-builtins.h b/sysdeps/s390/fpu/math-use-builtins.h
index 5435cbb..a39715c 100644
--- a/sysdeps/s390/fpu/math-use-builtins.h
+++ b/sysdeps/s390/fpu/math-use-builtins.h
@@ -42,16 +42,22 @@
 # define USE_CEILF_BUILTIN 1
 # define USE_CEILL_BUILTIN 1
 
+# define USE_TRUNC_BUILTIN 1
+# define USE_TRUNCF_BUILTIN 1
+# define USE_TRUNCL_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
 # 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
 # endif
 
 #else
@@ -77,6 +83,11 @@
 # define USE_CEILL_BUILTIN 0
 # define USE_CEILF128_BUILTIN 0
 
+# define USE_TRUNC_BUILTIN 0
+# define USE_TRUNCF_BUILTIN 0
+# define USE_TRUNCL_BUILTIN 0
+# define USE_TRUNCF128_BUILTIN 0
+
 #endif /* ! HAVE_S390_MIN_Z196_ZARCH_ASM_SUPPORT  */
 
 #endif /* math-use-builtins.h */