gcc 4.8 -O3 build:
00000000006f3dd0 <_ZN6pystonL21_checkUnpackingLengthEll>:
6f3dd0: 48 39 fe cmp %rdi,%rsi
6f3dd3: 74 4b je 6f3e20 <_ZN6pystonL21_checkUnpackingLengthEll+0x50>
6f3dd5: 55 push %rbp
1 6f3dd6: 48 89 e5 mov %rsp,%rbp
2 6f3dd9: 7f 47 jg 6f3e22 <_ZN6pystonL21_checkUnpackingLengthEll+0x52>
6f3ddb: 48 83 fe 01 cmp $0x1,%rsi
6f3ddf: 74 1f je 6f3e00 <_ZN6pystonL21_checkUnpackingLengthEll+0x30>
6f3de1: 48 8b 3d f8 00 10 01 mov 0x11000f8(%rip),%rdi # 17f3ee0 <PyExc_ValueError>
6f3de8: 48 89 f2 mov %rsi,%rdx
6f3deb: 31 c0 xor %eax,%eax
6f3ded: be 20 4d 1f 01 mov $0x11f4d20,%esi
6f3df2: e8 39 c6 01 00 callq 710430 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
6f3df7: 66 0f 1f 84 00 00 00 nopw 0x0(%rax,%rax,1)
6f3dfe: 00 00
6f3e00: 48 8b 3d d9 00 10 01 mov 0x11000d9(%rip),%rdi # 17f3ee0 <PyExc_ValueError>
6f3e07: ba 01 00 00 00 mov $0x1,%edx
6f3e0c: be f8 4c 1f 01 mov $0x11f4cf8,%esi
6f3e11: 31 c0 xor %eax,%eax
6f3e13: e8 18 c6 01 00 callq 710430 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
6f3e18: 0f 1f 84 00 00 00 00 nopl 0x0(%rax,%rax,1)
6f3e1f: 00
3 6f3e20: f3 c3 repz retq
4 6f3e22: 48 8b 3d b7 00 10 01 mov 0x11000b7(%rip),%rdi # 17f3ee0 <PyExc_ValueError>
6f3e29: be 5d 3a 22 01 mov $0x1223a5d,%esi
6f3e2e: 31 c0 xor %eax,%eax
6f3e30: e8 fb c5 01 00 callq 710430 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
6f3e35: 66 66 2e 0f 1f 84 00 data32 nopw %cs:0x0(%rax,%rax,1)
6f3e3c: 00 00 00 00
0001e620 0000000000000024 0001e624 FDE cie=00000000 pc=00000000006f3dd0..00000000006f3e35
1 DW_CFA_advance_loc: 6 to 00000000006f3dd6
DW_CFA_def_cfa_offset: 16
DW_CFA_offset: r6 (rbp) at cfa-16
2 DW_CFA_advance_loc: 3 to 00000000006f3dd9
DW_CFA_def_cfa_register: r6 (rbp)
3 DW_CFA_advance_loc1: 71 to 00000000006f3e20
DW_CFA_def_cfa: r7 (rsp) ofs 8
DW_CFA_restore: r6 (rbp)
4 DW_CFA_advance_loc: 2 to 00000000006f3e22
DW_CFA_def_cfa: r6 (rbp) ofs 16
DW_CFA_offset: r6 (rbp) at cfa-16
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
gcc 4.8 -O3 -fprofile-generate build:
00000000008e2100 <_ZN6pystonL21_checkUnpackingLengthEll>:
8e2100: 48 39 fe cmp %rdi,%rsi
8e2103: 74 4b je 8e2150 <_ZN6pystonL21_checkUnpackingLengthEll+0x50>
8e2105: 55 push %rbp
1 8e2106: 48 89 e5 mov %rsp,%rbp
2 8e2109: 7f 4e jg 8e2159 <_ZN6pystonL21_checkUnpackingLengthEll+0x59>
8e210b: 48 83 fe 01 cmp $0x1,%rsi
8e210f: 74 1f je 8e2130 <_ZN6pystonL21_checkUnpackingLengthEll+0x30>
8e2111: 48 8b 3d 08 25 ba 01 mov 0x1ba2508(%rip),%rdi # 2484620 <PyExc_ValueError>
8e2118: 48 89 f2 mov %rsi,%rdx
8e211b: 31 c0 xor %eax,%eax
8e211d: be 48 02 ae 01 mov $0x1ae0248,%esi
8e2122: 48 83 05 ce 56 5c 02 01 addq $0x1,0x25c56ce(%rip) # 2ea77f8 <__gcov0._ZN6pystonL21_checkUnpackingLengthEll+0x18>
8e212a: e8 d1 ef 02 00 callq 911100 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
8e212f: 90 nop
8e2130: 48 8b 3d e9 24 ba 01 mov 0x1ba24e9(%rip),%rdi # 2484620 <PyExc_ValueError>
8e2137: ba 01 00 00 00 mov $0x1,%edx
8e213c: be 20 02 ae 01 mov $0x1ae0220,%esi
8e2141: 31 c0 xor %eax,%eax
8e2143: 48 83 05 a5 56 5c 02 01 addq $0x1,0x25c56a5(%rip) # 2ea77f0 <__gcov0._ZN6pystonL21_checkUnpackingLengthEll+0x10>
8e214b: e8 b0 ef 02 00 callq 911100 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
3 8e2150: 48 83 05 88 56 5c 02 01 addq $0x1,0x25c5688(%rip) # 2ea77e0 <__gcov0._ZN6pystonL21_checkUnpackingLengthEll>
8e2158: c3 retq
4 8e2159: 48 8b 3d c0 24 ba 01 mov 0x1ba24c0(%rip),%rdi # 2484620 <PyExc_ValueError>
8e2160: be 24 db b1 01 mov $0x1b1db24,%esi
8e2165: 31 c0 xor %eax,%eax
8e2167: 48 83 05 79 56 5c 02 01 addq $0x1,0x25c5679(%rip) # 2ea77e8 <__gcov0._ZN6pystonL21_checkUnpackingLengthEll+0x8>
8e216f: e8 8c ef 02 00 callq 911100 <_ZN6pyston14raiseExcHelperEPNS_10BoxedClassEPKcz>
8e2174: 66 66 66 2e 0f 1f 84 data32 data32 nopw %cs:0x0(%rax,%rax,1)
8e217b: 00 00 00 00 00
0002e178 0000000000000024 0002e17c FDE cie=00000000 pc=00000000008e2100..00000000008e2174
1 DW_CFA_advance_loc: 6 to 00000000008e2106
DW_CFA_def_cfa_offset: 16
DW_CFA_offset: r6 (rbp) at cfa-16
2 DW_CFA_advance_loc: 3 to 00000000008e2109
DW_CFA_def_cfa_register: r6 (rbp)
3 DW_CFA_advance_loc1: 71 to 00000000008e2150
DW_CFA_def_cfa: r7 (rsp) ofs 8
DW_CFA_restore: r6 (rbp)
4 DW_CFA_advance_loc: 9 to 00000000008e2159
DW_CFA_def_cfa: r6 (rbp) ofs 16
DW_CFA_offset: r6 (rbp) at cfa-16
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
the eh_frame has nearly the same advance_locs in both pgo and non-pgo builds. 6, 3, 71, and 2/9.
advance_loc #3 and #4 correspond to the retq and the instruction following the retq in the non-pgo build
but in the pgo build #3 doesn’t correspond to the retq anymore. it’s the addq for the gconv counter