[Bug target/52624] New: Missing __builtin_bswap16

["hjl.tools at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52624

             Bug #: 52624
           Summary: Missing __builtin_bswap16
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: hjl.tools@gmail.com
                CC: ubizjak@gmail.com
            Target: x86


__builtin_bswap16 is supported on Powerpc, but is missing on x86.
We can use __builtin_bswap32 (x << 16).  But it it is less
efficient:

[hjl@gnu-6 tmp]$ cat b.c
#include <byteswap.h>

short
b1 (short x)
{
  return  __bswap_16 (x);
}

short
b2 (short x)
{
  return  __builtin_bswap32 (x << 16);
}
[hjl@gnu-6 tmp]$ gcc -S -O b.c
[hjl@gnu-6 tmp]$ cat b.s
    .file    "b.c"
    .text
    .globl    b1
    .type    b1, @function
b1:
.LFB0:
    .cfi_startproc
    movl    %edi, %eax
#APP
# 6 "b.c" 1
    rorw $8, %ax
# 0 "" 2
#NO_APP
    ret
    .cfi_endproc
.LFE0:
    .size    b1, .-b1
    .globl    b2
    .type    b2, @function
b2:
.LFB1:
    .cfi_startproc
    movl    %edi, %eax
    sall    $16, %eax
    bswap    %eax
    ret
    .cfi_endproc
.LFE1:
    .size    b2, .-b2
    .ident    "GCC: (GNU) 4.6.3 20120306 (Red Hat 4.6.3-2)"
    .section    .note.GNU-stack,"",@progbits
[hjl@gnu-6 tmp]$