[Bug target/115102] [SH] GCC misunderstands swap.b instruction

[ubizjak at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115102

--- Comment #4 from Uroš Bizjak <ubizjak at gmail dot com> ---
(In reply to Richard Biener from comment #1)
> though on x86 there's no high word preserving swap of the lower 2 bytes.

There is, please try:

  asm ("xchgb %h0, %b0" : "+Q" (val));

like:

--cut here--
#include <stdint.h>
#include <stdio.h>

uint32_t __attribute__((noinline))
bswap8(uint32_t val)
{
  return (val & 0xffff0000) | ((val & 0xff00) >> 8) | ((val & 0xff) << 8);
}

uint32_t __attribute__((noinline))
bswap8_new(uint32_t val)
{
  asm ("xchgb %h0, %b0" : "+Q" (val));

  return val;
}


int main ()
{
  uint32_t a = 0x10325476;

  printf ("%x %x\n", bswap8 (a), bswap8_new (a));

  return 0;
}
--cut here--

we already have:

(define_insn "bswaphi_lowpart"
  [(set (strict_low_part (match_operand:HI 0 "register_operand" "+Q,r"))
        (bswap:HI (match_dup 0)))
   (clobber (reg:CC FLAGS_REG))]
  ""
  "@
    xchg{b}\t{%h0, %b0|%b0, %h0}
    rol{w}\t{$8, %0|%0, 8}"

but bswaphi2 named pattern is enabled only for TARGET_MOVBE.

Time to fix this ;)