https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101701
Andrew Pinski <pinskia at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Ever confirmed|0 |1
Last reconfirmed| |2021-07-30
Status|UNCONFIRMED |NEW
Severity|normal |enhancement
--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
So the problem here is iftoswitch should ignore if it is profitable to convert
the ifs to a switch statement (unless there are only two ifs) and then allow
the switchlower pass to lower the switch again.
I thought there was a bug about this already too.
What is interesting is that the cost for ifs are so high on arm target
(compared to a switch), we end up with the best code already:
foo(int):
subs r3, r0, #1
cmp r3, #3
it hi
movhi r0, #-1
bx lr
bar(int):
subs r3, r0, #1
cmp r3, #3
it hi
movhi r0, #-1
bx lr
baz(int):
subs r3, r0, #1
cmp r3, #4
it cs
movcs r0, #-1
bx lr
:)
So x86 we get:
;; Canonical GIMPLE case clusters: 1 2 3 4
For foo
and then for bar:
;; Canonical GIMPLE case clusters: 1 2 3 4
;; BT can be built: BT(values:4 comparisons:8 range:4 density: 200.00%):1-4
/app/example.cpp:10:21: optimized: Condition chain with 4 BBs transformed into
a switch statement.
