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[4/4] math: Optimize float ilogb/llogb

Message ID 20250425205309.3866442-5-adhemerval.zanella@linaro.org
State New
Headers show
Series Remove UB and optimize ilogbf/ilogb | expand

Commit Message

Adhemerval Zanella April 25, 2025, 8:44 p.m. UTC 
By removing the wrapper and setting FE_INVALID and errno inline.

Checked on aarch64-linux-gnu and x86_64-linux-gnu.
---
 sysdeps/ieee754/flt-32/e_ilogbf.c | 42 +------------------
 sysdeps/ieee754/flt-32/w_ilogbf.c | 70 +++++++++++++++++++++++++++++++
 sysdeps/ieee754/flt-32/w_llogbf.c |  2 +
 3 files changed, 73 insertions(+), 41 deletions(-)
 create mode 100644 sysdeps/ieee754/flt-32/w_ilogbf.c
 create mode 100644 sysdeps/ieee754/flt-32/w_llogbf.c
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Patch

diff --git a/sysdeps/ieee754/flt-32/e_ilogbf.c b/sysdeps/ieee754/flt-32/e_ilogbf.c
index 024b114638..a27fb94732 100644
--- a/sysdeps/ieee754/flt-32/e_ilogbf.c
+++ b/sysdeps/ieee754/flt-32/e_ilogbf.c
@@ -1,41 +1 @@ 
-/* Get integer exponent of a floating-point value.
-   Copyright (C) 1999-2025 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <https://www.gnu.org/licenses/>.  */
-
-#include <limits.h>
-#include <math.h>
-#include <stdbit.h>
-#include "math_config.h"
-
-int
-__ieee754_ilogbf (float x)
-{
-  uint32_t ux = asuint (x);
-  int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
-  if (ex == 0) /* zero or subnormal */
-    {
-      /* Clear sign and exponent.  */
-      ux <<= 1 + EXPONENT_WIDTH;
-      if (ux == 0)
-	return FP_ILOGB0;
-      /* sbunormal */
-      return -127 - stdc_leading_zeros (ux);
-    }
-  if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
-    return ux << (1 + EXPONENT_WIDTH) ? FP_ILOGBNAN : INT_MAX;
-  return ex - 127;
-}
+/* ilogbf is implemented at w_ilogbf.c  */
diff --git a/sysdeps/ieee754/flt-32/w_ilogbf.c b/sysdeps/ieee754/flt-32/w_ilogbf.c
new file mode 100644
index 0000000000..21e40c7721
--- /dev/null
+++ b/sysdeps/ieee754/flt-32/w_ilogbf.c
@@ -0,0 +1,70 @@ 
+/* Get integer exponent of a floating-point value.
+   Copyright (C) 1999-2025 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <fenv.h>
+#include <errno.h>
+#include <limits.h>
+#include <math.h>
+#include <stdbit.h>
+#include <libm-alias-float.h>
+#include <math-type-macros-float.h>
+#include "math_config.h"
+
+#ifdef DEF_AS_LLOGBF
+# define IMPL_NAME   __llogb
+# define FUNC_NAME   llogb
+# define RET_TYPE    long int
+# define RET_LOGB0   FP_LLOGB0
+# define RET_LOGBNAN FP_LLOGBNAN
+# define RET_LOGMAX  LONG_MAX
+#else
+# define IMPL_NAME   __ilogb
+# define FUNC_NAME   ilogb
+# define RET_TYPE    int
+# define RET_LOGB0   FP_ILOGB0
+# define RET_LOGBNAN FP_ILOGBNAN
+# define RET_LOGMAX  INT_MAX
+#endif
+
+static inline RET_TYPE
+invalid_ret (RET_TYPE r)
+{
+  __set_errno (EDOM);
+  __feraiseexcept (FE_INVALID);
+  return r;
+}
+
+RET_TYPE
+M_DECL_FUNC (IMPL_NAME) (float x)
+{
+  uint32_t ux = asuint (x);
+  int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
+  if (ex == 0) /* zero or subnormal */
+    {
+      /* Clear sign and exponent.  */
+      ux <<= 1 + EXPONENT_WIDTH;
+      if (ux == 0)
+	return invalid_ret (RET_LOGB0);
+      /* sbunormal */
+      return (RET_TYPE)-127 - stdc_leading_zeros (ux);
+    }
+  if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
+    return invalid_ret (ux << (1 + EXPONENT_WIDTH) ? RET_LOGBNAN : RET_LOGMAX);
+  return ex - 127;
+}
+libm_alias_float (IMPL_NAME, FUNC_NAME);
diff --git a/sysdeps/ieee754/flt-32/w_llogbf.c b/sysdeps/ieee754/flt-32/w_llogbf.c
new file mode 100644
index 0000000000..8676434f6e
--- /dev/null
+++ b/sysdeps/ieee754/flt-32/w_llogbf.c
@@ -0,0 +1,2 @@ 
+#define DEF_AS_LLOGBF
+#include "w_ilogbf.c"