http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44281
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Keywords| |ra
--- Comment #14 from Steven Bosscher <steven at gcc dot gnu.org> 2013-02-23
14:55:53 UTC ---
(In reply to comment #10)
GCC 4.8 r196182, all at -O3 and verified that -Os is similar:
0000000000400470 <optimal_code_generation>:
400470: 48 8b 45 08 mov 0x8(%rbp),%rax
400474: ff e0 jmpq *%rax
...
0000000000400480 <unmodified_input_arg_is_copied>:
400480: 4c 8b 55 08 mov 0x8(%rbp),%r10
400484: 48 8d 6d 08 lea 0x8(%rbp),%rbp
400488: 41 ff e2 jmpq *%r10
...
0000000000400490 <unmodified_input_arg_is_copied_alt>:
400490: 48 8b 45 08 mov 0x8(%rbp),%rax
400494: 48 83 c5 08 add $0x8,%rbp
400498: ff e0 jmpq *%rax
...
00000000004004a0 <unmodified_input_arg_is_copied_alt2>:
4004a0: 48 8b 45 08 mov 0x8(%rbp),%rax
4004a4: 48 83 c5 08 add $0x8,%rbp
4004a8: ff e0 jmpq *%rax
...
The reported slowdown in comment #5 is also gone.
For the original complaint, comment #0:
0000000000000000 <push_flag_into_global_reg_var>:
0: 31 c0 xor %eax,%eax
2: 48 89 da mov %rbx,%rdx
5: 48 39 f7 cmp %rsi,%rdi
8: 0f 94 c0 sete %al
b: 48 c1 e2 08 shl $0x8,%rdx
f: 48 09 d0 or %rdx,%rax
12: 48 89 c3 mov %rax,%rbx
15: c3 retq
...
0000000000000020 <push_flag_into_local_var>:
20: 31 c0 xor %eax,%eax
22: 48 39 f7 cmp %rsi,%rdi
25: 0f 94 c0 sete %al
28: 48 c1 e2 08 shl $0x8,%rdx
2c: 48 09 d0 or %rdx,%rax
2f: c3 retq
So the code for push_flag_into_local_var is the same as gcc-3.3 and the
code for push_flag_into_global_reg_var is the same as gcc-4.4.
