On Thu, 28 Oct 2021, Jakub Jelinek wrote:
> On Thu, Oct 28, 2021 at 02:24:23PM +0200, Richard Biener wrote:
> > I'm not able to trigger unsigned_float to be used, even when
> > converting 0x8000000000000001 I get (float:DF (reg:DI...))
> > on x86_64 because we emit conditional code that will end up
> > using some compensation to emulate unsigned_float with
> > float with some tricks that do not necessarily look safe
> > from a rounding perspective (so maybe x86 would need to
> > resort to soft-fp here?):
> >
> > movabsq $4611686018427387905, %rax
> > cvtsi2sdq %rax, %xmm0
> > addsd %xmm0, %xmm0
> > ucomisd .LC0(%rip), %xmm0
> >
> > the constant is (0x8000000000000001u >> 1) | 1
>
> Missing -mavx512f ?
Yeah, but I have no way to test AVX512 (well, I might try SDE but not
sure whether that handles rounding modes ;)) OK, so just trying
with that the -2 testcase indeed FAILs without the unsigned_float
hunk but succeeds with. It also oddly succeeds with or without
the patch and the floatunsdidf emulation.
> (define_expand "floatunsdidf2"
> [(set (match_operand:DF 0 "register_operand")
> (unsigned_float:DF
> (match_operand:DI 1 "nonimmediate_operand")))]
> "((TARGET_64BIT && TARGET_AVX512F)
> || TARGET_KEEPS_VECTOR_ALIGNED_STACK)
> && TARGET_SSE2 && TARGET_SSE_MATH"
> {
> if (!TARGET_64BIT)
> {
> ix86_expand_convert_uns_didf_sse (operands[0], operands[1]);
> DONE;
> }
> if (!TARGET_AVX512F)
> {
> x86_emit_floatuns (operands);
> DONE;
> }
> })
> where x86_emit_floatuns emits that emulation?
> Anyway, what the testcase probably needs to do is this
> (set (reg:DI temp1) (const_int ...))
> (set (reg:DF temp2) (unsigned_float:DF (reg:DI temp1))) ! And also float
> separately too
> (set (reg:DI temp3) (subreg:DF (reg:DF temp2)))
> or something similar so that during combine it is not rejected because
> it is not valid to have the DFmode constants as immediates and they'd need
> to go into memory instead. But the subreg might not be valid too.
> So perhaps some different target.
> Yet another option would be a self-test...
>
> But if you don't have time for the testcase right now, let's just
> handle it in UNSIGNED_FLOAT too and I can try to look at the testcase
> later?
Sure, that works for me. See the patch I posted which is now in
re-testing.
Thanks,
Richard.
