https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115819
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2024-07-07
Blocks| |53947
Severity|normal |enhancement
Ever confirmed|0 |1
Target|Riscv |Riscv aarch64
Status|UNCONFIRMED |NEW
Component|target |tree-optimization
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
vect__4.9_41 = VEC_PERM_EXPR <vect__4.8_40, vect__4.8_40, { POLY_INT_CST [3,
4], POLY_INT_CST [2, 4], POLY_INT_CST [1, 4], ... }>;
vect__5.10_43 = vect__4.9_41 + { 1, ... };
vect__5.13_50 = VEC_PERM_EXPR <vect__5.10_43, vect__5.10_43, { POLY_INT_CST
[3, 4], POLY_INT_CST [2, 4], POLY_INT_CST [1, 4], ... }>;
Well the vrgather here should not be needed in the first place.
We have:
vrgather.vv v1,v3,v5
vadd.vi v1,v1,1
vrgather.vv v3,v1,v5
For aarch64 we get:
rev z31.s, z31.s // 32 [c=4 l=4] aarch64_sve_revvnx4si
add z31.s, z31.s, #1 // 33 [c=12 l=4] addvnx4si3/0
rev z31.s, z31.s // 34 [c=4 l=4] aarch64_sve_revvnx4si
But the 2 revs are not neded, just like the 2 vrgather.vv are not needed.
For aarch64 (without SVE) we get just as bad (maybe worse) code generation:
tbl v29.16b, {v30.16b - v31.16b}, v27.16b // 36 [c=4 l=4]
aarch64_qtbl2v16qi
add v29.4s, v29.4s, v26.4s // 38 [c=8 l=4] addv4si3
mov v28.16b, v29.16b // 116 [c=4 l=4]
*aarch64_simd_movv16qi/3
tbl v25.16b, {v28.16b - v29.16b}, v27.16b // 43 [c=4 l=4]
aarch64_qtbl2v16qi
The TBL are not needed.
I thought I saw this before too ...
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
