Maybe comments at the insn pattern who emit "rep\; ret" can explain it: ";; Used by x86_machine_dependent_reorg to avoid penalty on single byte RET ;; instruction Athlon and K8 have."
Thanks - Joey -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Etienne Lorrain Sent: 2008年12月4日 18:31 To: gcc@gcc.gnu.org Subject: ia32 gcc-Debian 4.3.2-1 "rep ret" ? Hello, I did not find any documentation of a "rep ret" instruction, at http://www.intel.com/design/processor/manuals/253667.pdf they just say: "The behavior of the REP prefix is undefined when used with non-strings instructions". Any pointers? Thanks, Etienne. etienne:~$ gcc --version gcc (Debian 4.3.2-1) 4.3.2 Copyright (C) 2008 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. etienne:~$ cat tmp.c void fct2(int); void fct (int i, int a) { a *= 2; if (i == 2) fct2(a); } etienne:~$ gcc -O2 -fomit-frame-pointer -S tmp.c -o tmp.s etienne:~$ cat tmp.s .file "tmp.c" .text .p2align 4,,15 .globl fct .type fct, @function fct: cmpl $2, 4(%esp) movl 8(%esp), %eax je .L5 rep ret .p2align 4,,7 .p2align 3 .L5: addl %eax, %eax movl %eax, 4(%esp) jmp fct2 .size fct, .-fct .ident "GCC: (Debian 4.3.2-1) 4.3.2" .section .note.GNU-stack,"",@progbits etienne:~$
