On Thu, May 28, 2026 at 10:14 AM Uros Bizjak <[email protected]> wrote:
>
> On Thu, May 28, 2026 at 9:45 AM Jakub Jelinek <[email protected]> wrote:
> >
> > Hi!
> >
> > The following testcase ICEs, because combine matches
> > (set (reg:DI 108) (plus:DI (reg:DI 104 [ s ]) (subreg:DI (reg:TI 103 [ _2
> > ]) 8)))
> > Now, because ix86_validate_address_register has:
> > 12038 /* Don't allow SUBREGs that span more than a word. It can
> > 12039 lead to spill failures when the register is one word out
> > 12040 of a two word structure. */
> > 12041 if (GET_MODE_SIZE (mode) > UNITS_PER_WORD)
> > 12042 return NULL_RTX;
> > this isn't recognized as *leadi, but is recognized as *adddi_1_nf pattern
> > instead. Now, later on the RA turns it into:
> > (set (reg:DI 2 cx [108]) (plus:DI (reg:DI 0 ax [orig:104 s ] [104]) (reg:DI
> > 5 di [ _2+8 ])))
> > which would be valid *leadi, but given that INSN_CODE is already set to the
> > *adddi_1_nf and that also satisfies it, nothing re-recognizes it as *leadi.
> > But in that case without TARGET_APX_NDD the pattern has return "#";
> > That is a bug, because there is no splitter to split that
> > (set (reg:DI 2 cx [108]) (plus:DI (reg:DI 0 ax [orig:104 s ] [104]) (reg:DI
> > 5 di [ _2+8 ])))
> > into itself so that it is re-recognized as *leadi, so it just ICEs.
> > I think having a splitter to split to the same thing would be just weird, so
> > this just outputs lea insn directly.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk/16/15?
> >
> > 2026-05-28 Jakub Jelinek <[email protected]>
> >
> > PR target/125469
> > * config/i386/i386.md (*add<mode>_1<nf_name>): Don't return "#" for
> > the lea non-TARGET_APX_NDD case, instead emit a lea directly.
> >
> > * gcc.target/i386/apx-nf-pr125469.c: New test.
>
> OK. I also wonder if the check in ix86_validate_address_register can
> be removed, there were many RA improvements in the last ... decade
> (?).
Hm, OTOH, is this condition correct:
case TYPE_LEA:
if (TARGET_APX_NDD && <nf_applied>)
return "%{nf%} add{<imodesuffix>}\t{%2, %1, %0|%0, %1, %2}";
else
return "#";
Should it be "TARGET_APX_NDD || <nf_applied>"?
We should split to LEA only when NF is not applied, otherwise we use
{nf} addq %rdi, %rax, %rcx
Uros.
