Hi!
This is a regression on some targets introduced I believe by r6-2055
which added mode argument to set_src_cost.
The problem here is that in the first iteration, mode is always QImode
and we get as -Os zero cost set_src_cost (const0_rtx, QImode, false).
But then we use the mode variable for iterating over int, partial int
and vector int modes, so for the second iteration we call set_src_cost
with mode which is at that time (machine_mode) (MAX_MODE_VECTOR_INT + 1).
In the x86 case that happens to be V2HFmode and we don't crash (and
compute the same 0 cost as we would for QImode).
But e.g. in the SPARC case (machine_mode) (MAX_MODE_VECTOR_INT + 1) is
MAX_MACHINE_MODE and that does all kinds of weird things especially
when doing ubsan bootstrap.
Fixed by always using QImode.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2025-04-14 Jakub Jelinek <ja...@redhat.com>
PR rtl-optimization/119785
* expmed.cc (init_expmed): Always pass QImode rather than mode to
set_src_cost passed to set_zero_cost.
--- gcc/expmed.cc.jj 2025-04-08 14:08:51.234282102 +0200
+++ gcc/expmed.cc 2025-04-14 12:17:48.334123928 +0200
@@ -285,7 +285,7 @@ init_expmed (void)
for (speed = 0; speed < 2; speed++)
{
crtl->maybe_hot_insn_p = speed;
- set_zero_cost (speed, set_src_cost (const0_rtx, mode, speed));
+ set_zero_cost (speed, set_src_cost (const0_rtx, QImode, speed));
for (mode = MIN_MODE_INT; mode <= MAX_MODE_INT;
mode = (machine_mode)(mode + 1))
Jakub
