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From: "crazylht at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug target/102473] [12 Regression] 521.wrf_r 5% slower at -Ofast
 and generic x86_64 tuning after r12-3426-g8f323c712ea76c
Date: Tue, 28 Sep 2021 02:20:29 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D102473

--- Comment #13 from Hongtao.liu <crazylht at gmail dot com> ---
(In reply to H.J. Lu from comment #12)
> Are glibc regressions real? Please show the affected glibc assembly codes
> before and after.

Assembly codes is the same, but DSB coverage drop down. before my commit=20
front-end bound of libc-2.31.so is 1.2%, after my commit front-end bound ra=
ise
up to 21.9%, use -falign-functions=3D64 doesn't help.

The below code is copy from one of libc functions which has big front-end
bounds

0x5f741 0       Block 123:=20=20=20=20=20=20
0x5f741 0       jz 0x607b0 <Block 379>  0
0x5f747 0       Block 124:=20=20=20=20=20=20
0x5f747 0       movq  -0x78(%rbp), %rdx 0
0x5f74b 0       Block 125:=20=20=20=20=20=20
0x5f74b 0       sub $0x1, %r14d 130500000
0x5f74f 0       cmp %rbx, %r15=20=20
0x5f752 0       jz 0x5f813 <Block 135>=20=20
0x5f758 0       Block 126:=20=20=20=20=20=20
0x5f758 0       movl  -0x98(%rbp), %ecx 0
0x5f75e 0       Block 127:=20=20=20=20=20=20
0x5f75e 0       movl  -0x8(%r15), %eax  29000000
0x5f762 0       sub $0x18, %r15 203000000
0x5f766 0       add %r12d, %eax 0
0x5f769 0       sub $0x1, %eax  58000000
0x5f76c 0       cmp %ecx, %eax  159500000
0x5f76e 0       jnle 0x5f74b <Block 125>        0
0x5f770 0       Block 128:=20=20=20=20=20=20
0x5f770 0       movq  -0x70(%rbp), %rdi 43500000
0x5f774 0       test %rdx, %rdx 29000000
0x5f777 0       jz 0x5f700 <Block 119>=