https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120067
Bug ID: 120067
Summary: RISC-V: x264 sub4x4_dct high icount
Product: gcc
Version: 15.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: parras at gcc dot gnu.org
Target Milestone: ---
Created attachment 61273
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=61273&action=edit
Detailed dump from the expand pass (RISC-V)
This is reduced from 525.x264_r's 4th hottest block:
https://godbolt.org/z/KdWv1er6f
AArch64 assembly is clean and efficient (35 insns) while RISC-V's is long and
messy (114 insns).
The most obvious issue is that it keeps spilling and reloading the same data
from the stack. Also I do not understand why we need those vslidedown.
A rapid look at the expand dump (see attachment) shows that the latter come
from VIEW_CONVERT_EXPR<vector(4) unsigned short>.
I will keep looking into this.
