https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110897
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Last reconfirmed| |2023-08-04
Target|riscv |riscv, x86_64-*-*
CC| |rsandifo at gcc dot gnu.org
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Blocks| |53947
Component|target |tree-optimization
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
it looks like you don't support vector short logical shift? For some reason
vect_recog_over_widening_pattern doesn't check whether the demoted operation
is supported ...
The following helps on x86_64, it disables the demotion. I think the idea
was that we eventually recognize a widening shift, so the narrow operation
itself doesn't need to be supported, but clearly that doesn't work out
when there is no such shift.
diff --git a/gcc/tree-vect-patterns.cc b/gcc/tree-vect-patterns.cc
index e4ab8c2d65b..4e4191652e3 100644
--- a/gcc/tree-vect-patterns.cc
+++ b/gcc/tree-vect-patterns.cc
@@ -3091,6 +3091,11 @@ vect_recog_over_widening_pattern (vec_info *vinfo,
if (!new_vectype || !op_vectype)
return NULL;
+ optab optab;
+ if (!(optab = optab_for_tree_code (code, op_vectype, optab_vector))
+ || optab_handler (optab, TYPE_MODE (op_vectype)) == CODE_FOR_nothing)
+ return NULL;
+
if (dump_enabled_p ())
dump_printf_loc (MSG_NOTE, vect_location, "demoting %T to %T\n",
type, new_type);
with the patch above x86 can vectorize both loops with AVX2 but not without.
Can you confirm this helps on RISC-V as well?
Richard, what was the idea here?
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations
