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[2/4] math: Optimize double ilogb/llogb

Message ID 20250425205309.3866442-3-adhemerval.zanella@linaro.org
State Superseded
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/dbl-64/e_ilogb.c | 42 +------------------
 sysdeps/ieee754/dbl-64/w_ilogb.c | 69 ++++++++++++++++++++++++++++++++
 sysdeps/ieee754/dbl-64/w_llogb.c |  2 +
 3 files changed, 72 insertions(+), 41 deletions(-)
 create mode 100644 sysdeps/ieee754/dbl-64/w_ilogb.c
 create mode 100644 sysdeps/ieee754/dbl-64/w_llogb.c
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Patch

diff --git a/sysdeps/ieee754/dbl-64/e_ilogb.c b/sysdeps/ieee754/dbl-64/e_ilogb.c
index 89e7498266..1ea2f23e2f 100644
--- a/sysdeps/ieee754/dbl-64/e_ilogb.c
+++ b/sysdeps/ieee754/dbl-64/e_ilogb.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_ilogb (double x)
-{
-  uint64_t ux = asuint64 (x);
-  int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
-  if (ex == 0) /* zero or subnormal */
-    {
-      /* Clear sign and exponent */
-      ux <<= 12;
-      if (ux == 0)
-	return FP_ILOGB0;
-      /* subnormal  */
-      return -1023 - stdc_leading_zeros (ux);
-    }
-  if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
-    return ux << 12 ? FP_ILOGBNAN : INT_MAX;
-  return ex - 1023;
-}
+/* ilogb is implemented at w_ilogb.c  */
diff --git a/sysdeps/ieee754/dbl-64/w_ilogb.c b/sysdeps/ieee754/dbl-64/w_ilogb.c
new file mode 100644
index 0000000000..45a59588c0
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/w_ilogb.c
@@ -0,0 +1,69 @@ 
+/* 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-double.h>
+#include "math_config.h"
+
+#ifdef DEF_AS_LLOGB
+# 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
+IMPL_NAME (double x)
+{
+  uint64_t ux = asuint64 (x);
+  int ex = (ux & ~SIGN_MASK) >> MANTISSA_WIDTH;
+  if (ex == 0) /* zero or subnormal */
+    {
+      /* Clear sign and exponent */
+      ux <<= 12;
+      if (ux == 0)
+	return invalid_ret (RET_LOGB0);
+      /* subnormal  */
+      return (RET_TYPE)-1023 - stdc_leading_zeros (ux);
+    }
+  if (ex == EXPONENT_MASK >> MANTISSA_WIDTH) /* NaN or Inf */
+    return invalid_ret (ux << 12 ? RET_LOGBNAN : RET_LOGMAX);
+  return ex - 1023;
+}
+libm_alias_double (IMPL_NAME, FUNC_NAME)
diff --git a/sysdeps/ieee754/dbl-64/w_llogb.c b/sysdeps/ieee754/dbl-64/w_llogb.c
new file mode 100644
index 0000000000..c984cd151a
--- /dev/null
+++ b/sysdeps/ieee754/dbl-64/w_llogb.c
@@ -0,0 +1,2 @@ 
+#define DEF_AS_LLOGB
+#include "w_ilogb.c"