Hi!
On Mon, Dec 07, 2020 at 03:27:14PM +0100, Uros Bizjak wrote:
> On Fri, Dec 4, 2020 at 7:26 PM Segher Boessenkool
> <seg...@kernel.crashing.org> wrote:
> > A splitter can *already* split to only one insn.
>
> Unfortunately, the attached patch with the following testcase:
>
> --cut here--
> int test (int a, int b)
> {
> return a << (b & 31);
> }
> --cut here--
>
> does not trigger the call to combine_split_insns. The reason in the
> following condition:
>
> /* If we were combining three insns and the result is a simple SET
> with no ASM_OPERANDS that wasn't recognized, try to split it into two
> insns. There are two ways to do this. It can be split using a
> machine-specific method (like when you have an addition of a large
> constant) or by combine in the function find_split_point. */
>
> if (i1 && insn_code_number < 0 && GET_CODE (newpat) == SET
> && asm_noperands (newpat) < 0)
>
> where i1 is null.
I see. We could also allow this for 2->2 combinations (w/ the same
restrictions we do for other 2->2 combinations, but that probably falls
out automatically).
This will need careful testing of course, but I don't expect anything
bad (famous last words of course).
Could you please open a PR for this? Just so I can keep track :-)
Segher
