https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116004
Bug ID: 116004
Summary: PPC64 vector Intrinsic vec_first_mismatch_or_eos_index
generates poor code
Product: gcc
Version: 13.2.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: munroesj at gcc dot gnu.org
Target Milestone: ---
GCC13 generates the following code for the intrinsic
vec_first_mismatch_or_eos_index -mcpu=power9 -O3:
00000000000000c0 <test_intrn_first_mismatch_or_eos_index_PWR9>:
c0: d1 02 00 f0 xxspltib vs32,0
c4: 07 00 22 10 vcmpneb v1,v2,v0
c8: 07 00 03 10 vcmpneb v0,v3,v0
cc: 07 19 42 10 vcmpnezb v2,v2,v3
d0: 17 04 21 f0 xxland vs33,vs33,vs32
d4: 57 0d 42 f0 xxlorc vs34,vs34,vs33
d8: 02 16 61 10 vctzlsbb r3,v2
dc: b4 07 63 7c extsw r3,r3
e0: 20 00 80 4e blr
The use of vcmpneb to compare for EOS is redundant to the vcmpnezb instruction
(which includes the EOS compares). The additional xxland/xxorc logic is only
necessary because of the extra vcmpneb compares.
All you need is a single vcmpnezb as it already handles the a/b mismatch and
EOS tests for both operands. For example:
0000000000000070 <test_vec_first_mismatch_byte_or_eos_index>:
70: 07 19 42 10 vcmpnezb v2,v2,v3
74: 02 16 61 10 vctzlsbb r3,v2
78: b4 07 63 7c extsw r3,r3
7c: 20 00 80 4e blr
