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glibc/sysdeps/m68k/m680x0/w_ilogb.c
Adhemerval Zanella c4be334400 math: Optimize double ilogb/llogb
It removes the wrapper by moving the error/EDOM handling to an
out-of-line implementation (__math_invalid_i/__math_invalid_li).
Also, __glibc_unlikely is used on errors case since it helps
code generation on recent gcc.

The code now builds to with gcc-14 on aarch64:

0000000000000000 <__ilogb>:
   0:   9e660000        fmov    x0, d0
   4:   d374f801        ubfx    x1, x0, #52, #11
   8:   340000e1        cbz     w1, 24 <__ilogb+0x24>
   c:   510ffc20        sub     w0, w1, #0x3ff
  10:   711ffc3f        cmp     w1, #0x7ff
  14:   54000040        b.eq    1c <__ilogb+0x1c>  // b.none
  18:   d65f03c0        ret
  1c:   12b00000        mov     w0, #0x7fffffff                 // #2147483647
  20:   14000000        b       0 <__math_invalid_i>
  24:   d374cc00        lsl     x0, x0, #12
  28:   b40000a0        cbz     x0, 3c <__ilogb+0x3c>
  2c:   dac01000        clz     x0, x0
  30:   12807fc1        mov     w1, #0xfffffc01                 // #-1023
  34:   4b000020        sub     w0, w1, w0
  38:   d65f03c0        ret
  3c:   320107e0        mov     w0, #0x80000001                 // #-2147483647
  40:   14000000        b       0 <__math_invalid_i>

Some ABI requires additional adjustments:

  * i386 and m68k requires to use the template version, since
    both provide __ieee754_ilogb implementatations.

  * loongarch uses a custom implementation as well.

  * powerpc64le also has a custom implementation for POWER9, which
    is also used for float and float128 version.  The generic
    e_ilogb.c implementation is moved on powerpc to keep the
    current code as-is.

Checked on aarch64-linux-gnu and x86_64-linux-gnu.

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>
2025-06-02 13:32:19 -03:00

3 lines
67 B
C

#include <math-type-macros-double.h>
#include <w_ilogb_template.c>