From a5b8dff144d01ecc5eb76a8e27f7a207a7200807 Mon Sep 17 00:00:00 2001
From: Xi Ruoyao <xry111@xry111.site>
Date: Wed, 9 Nov 2022 02:01:32 +0800
Subject: [PATCH 4/5] math: Allow using compiler builtins for logb{,f}

---
 sysdeps/generic/math-use-builtins-logb.h | 2 ++
 sysdeps/generic/math-use-builtins.h      | 1 +
 sysdeps/ieee754/dbl-64/s_logb.c          | 5 +++++
 sysdeps/ieee754/flt-32/s_logbf.c         | 5 +++++
 4 files changed, 13 insertions(+)
 create mode 100644 sysdeps/generic/math-use-builtins-logb.h

diff --git a/sysdeps/generic/math-use-builtins-logb.h b/sysdeps/generic/math-use-builtins-logb.h
new file mode 100644
index 0000000000..f8fc9ae7cb
--- /dev/null
+++ b/sysdeps/generic/math-use-builtins-logb.h
@@ -0,0 +1,2 @@
+#define USE_LOGB_BUILTIN 0
+#define USE_LOGBF_BUILTIN 0
diff --git a/sysdeps/generic/math-use-builtins.h b/sysdeps/generic/math-use-builtins.h
index 3acec1d538..a9cd510c2a 100644
--- a/sysdeps/generic/math-use-builtins.h
+++ b/sysdeps/generic/math-use-builtins.h
@@ -38,5 +38,6 @@
 #include <math-use-builtins-fmin.h>
 #include <math-use-builtins-fabs.h>
 #include <math-use-builtins-lrint.h>
+#include <math-use-builtins-logb.h>
 
 #endif /* MATH_USE_BUILTINS_H  */
diff --git a/sysdeps/ieee754/dbl-64/s_logb.c b/sysdeps/ieee754/dbl-64/s_logb.c
index 82cabd206a..a9b18bf97b 100644
--- a/sysdeps/ieee754/dbl-64/s_logb.c
+++ b/sysdeps/ieee754/dbl-64/s_logb.c
@@ -21,10 +21,14 @@
 #include <math_private.h>
 #include <libm-alias-double.h>
 #include <fix-int-fp-convert-zero.h>
+#include <math-use-builtins.h>
 
 double
 __logb (double x)
 {
+#if USE_LOGB_BUILTIN
+  return __builtin_logb (x);
+#else
   int64_t ix, ex;
 
   EXTRACT_WORDS64 (ix, x);
@@ -42,6 +46,7 @@ __logb (double x)
   if (FIX_INT_FP_CONVERT_ZERO && ex == 1023)
     return 0.0;
   return (double) (ex - 1023);
+#endif
 }
 #ifndef __logb
 libm_alias_double (__logb, logb)
diff --git a/sysdeps/ieee754/flt-32/s_logbf.c b/sysdeps/ieee754/flt-32/s_logbf.c
index a06f975797..cf58596c8f 100644
--- a/sysdeps/ieee754/flt-32/s_logbf.c
+++ b/sysdeps/ieee754/flt-32/s_logbf.c
@@ -16,10 +16,14 @@
 #include <math_private.h>
 #include <libm-alias-float.h>
 #include <fix-int-fp-convert-zero.h>
+#include <math-use-builtins.h>
 
 float
 __logbf (float x)
 {
+#if USE_LOGBF_BUILTIN
+  return __builtin_logbf (x);
+#else
   int32_t ix, rix;
 
   GET_FLOAT_WORD (ix, x);
@@ -37,5 +41,6 @@ __logbf (float x)
   if (FIX_INT_FP_CONVERT_ZERO && rix == 127)
     return 0.0f;
   return (float) (rix - 127);
+#endif
 }
 libm_alias_float (__logb, logb)
-- 
2.37.0