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: unassig...@gcc.gnu.org ReportedBy: hjl.to...@gmail.com CC: ubiz...@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 $16, %eax bswap %eax ret .cfi_endproc .LFE1: .size b2, .-b2 .ident "GCC: (GNU) 4.6.3 20120306 (Red Hat 4.6.3-2)" .section .note.GNU-stack,"",@progbits [hjl@gnu-6 tmp]$