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glibc/sysdeps/m68k
Adhemerval Zanella 39775f00b1 math: Optimize float ilogb/llogb
It removes the wrapper by moving the error/EDOM handling to an
out-of-line implementation (__math_invalidf_i/__math_invalidf_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 <__ilogbf>:
   0:   1e260000        fmov    w0, s0
   4:   d3577801        ubfx    x1, x0, #23, #8
   8:   340000e1        cbz     w1, 24 <__ilogbf+0x24>
   c:   5101fc20        sub     w0, w1, #0x7f
  10:   7103fc3f        cmp     w1, #0xff
  14:   54000040        b.eq    1c <__ilogbf+0x1c>  // b.none
  18:   d65f03c0        ret
  1c:   12b00000        mov     w0, #0x7fffffff                 // #2147483647
  20:   14000000        b       0 <__math_invalidf_i>
  24:   53175800        lsl     w0, w0, #9
  28:   340000a0        cbz     w0, 3c <__ilogbf+0x3c>
  2c:   5ac01000        clz     w0, w0
  30:   12800fc1        mov     w1, #0xffffff81                 // #-127
  34:   4b000020        sub     w0, w1, w0
  38:   d65f03c0        ret
  3c:   320107e0        mov     w0, #0x80000001                 // #-2147483647
  40:   14000000        b       0 <__math_invalidf_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
..
2025-06-02 13:32:19 -03:00
2023-07-17 10:08:10 -04:00
2023-07-17 10:08:10 -04:00