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From: Richard Sandiford <richard.sandiford@arm.com>
To: Richard Biener <richard.guenther@gmail.com>
Cc: Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org>,
	 liuhongt <hongtao.liu@intel.com>,
	 crazylht@gmail.com,  hjl.tools@gmail.com
Subject: Re: [PATCH] [vect]Use intermiediate integer type for float_expr/fix_trunc_expr when direct optab is not existed.
Date: Wed, 21 Jun 2023 12:20:25 +0100	[thread overview]
Message-ID: <mptedm583k6.fsf@arm.com> (raw)
In-Reply-To: <CAFiYyc0axUY7PiDG-teCDqbkR4bbW1-NhyxOPuZM50r0BwgLTw@mail.gmail.com> (Richard Biener's message of "Wed, 21 Jun 2023 13:04:28 +0200")

Richard Biener <richard.guenther@gmail.com> writes:
> On Wed, Jun 21, 2023 at 11:32 AM Richard Sandiford
> <richard.sandiford@arm.com> wrote:
>>
>> Richard Sandiford <richard.sandiford@arm.com> writes:
>> > Richard Biener via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>> >> On Fri, Jun 2, 2023 at 3:01 AM liuhongt via Gcc-patches
>> >> <gcc-patches@gcc.gnu.org> wrote:
>> >>>
>> >>> We have already use intermidate type in case WIDEN, but not for NONE,
>> >>> this patch extended that.
>> >>>
>> >>> I didn't do that in pattern recog since we need to know whether the
>> >>> stmt belongs to any slp_node to decide the vectype, the related optabs
>> >>> are checked according to vectype_in and vectype_out. For non-slp case,
>> >>> vec_pack/unpack are always used when lhs has different size from rhs,
>> >>> for slp case, sometimes vec_pack/unpack is used, somethings
>> >>> direct conversion is used.
>> >>>
>> >>> Bootstrapped and regtested on x86_64-pc-linux-gnu{-m32,}.
>> >>> Ok for trunk?
>> >>>
>> >>> gcc/ChangeLog:
>> >>>
>> >>>         PR target/110018
>> >>>         * tree-vect-stmts.cc (vectorizable_conversion): Use
>> >>>         intermiediate integer type for float_expr/fix_trunc_expr when
>> >>>         direct optab is not existed.
>> >>>
>> >>> gcc/testsuite/ChangeLog:
>> >>>
>> >>>         * gcc.target/i386/pr110018-1.c: New test.
>> >>> ---
>> >>>  gcc/testsuite/gcc.target/i386/pr110018-1.c | 94 ++++++++++++++++++++++
>> >>>  gcc/tree-vect-stmts.cc                     | 56 ++++++++++++-
>> >>>  2 files changed, 149 insertions(+), 1 deletion(-)
>> >>>  create mode 100644 gcc/testsuite/gcc.target/i386/pr110018-1.c
>> >>>
>> >>> diff --git a/gcc/testsuite/gcc.target/i386/pr110018-1.c b/gcc/testsuite/gcc.target/i386/pr110018-1.c
>> >>> new file mode 100644
>> >>> index 00000000000..b1baffd7af1
>> >>> --- /dev/null
>> >>> +++ b/gcc/testsuite/gcc.target/i386/pr110018-1.c
>> >>> @@ -0,0 +1,94 @@
>> >>> +/* { dg-do compile } */
>> >>> +/* { dg-options "-mavx512fp16 -mavx512vl -O2 -mavx512dq" } */
>> >>> +/* { dg-final { scan-assembler-times {(?n)vcvttp[dsh]2[dqw]} 5 } } */
>> >>> +/* { dg-final { scan-assembler-times {(?n)vcvt[dqw]*2p[dsh]} 5 } } */
>> >>> +
>> >>> +void
>> >>> +foo (double* __restrict a, char* b)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo1 (float* __restrict a, char* b)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo2 (_Float16* __restrict a, char* b)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +  a[4] = b[4];
>> >>> +  a[5] = b[5];
>> >>> +  a[6] = b[6];
>> >>> +  a[7] = b[7];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo3 (double* __restrict a, short* b)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo4 (float* __restrict a, char* b)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo5 (double* __restrict b, char* a)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo6 (float* __restrict b, char* a)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo7 (_Float16* __restrict b, char* a)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +  a[4] = b[4];
>> >>> +  a[5] = b[5];
>> >>> +  a[6] = b[6];
>> >>> +  a[7] = b[7];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo8 (double* __restrict b, short* a)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +}
>> >>> +
>> >>> +void
>> >>> +foo9 (float* __restrict b, char* a)
>> >>> +{
>> >>> +  a[0] = b[0];
>> >>> +  a[1] = b[1];
>> >>> +  a[2] = b[2];
>> >>> +  a[3] = b[3];
>> >>> +}
>> >>> diff --git a/gcc/tree-vect-stmts.cc b/gcc/tree-vect-stmts.cc
>> >>> index bd3b07a3aa1..1118c89686d 100644
>> >>> --- a/gcc/tree-vect-stmts.cc
>> >>> +++ b/gcc/tree-vect-stmts.cc
>> >>> @@ -5162,6 +5162,49 @@ vectorizable_conversion (vec_info *vinfo,
>> >>>         return false;
>> >>>        if (supportable_convert_operation (code, vectype_out, vectype_in, &code1))
>> >>>         break;
>> >>
>> >> A comment would be nice here.  Like
>> >>
>> >>    /* For conversions between float and smaller integer types try whether we can
>> >>       use intermediate signed integer types to support the conversion.  */
>> >>
>> >>> +      if ((code == FLOAT_EXPR
>> >>> +          && GET_MODE_SIZE (lhs_mode) > GET_MODE_SIZE (rhs_mode))
>> >>> +         || (code == FIX_TRUNC_EXPR
>> >>> +             && GET_MODE_SIZE (rhs_mode) > GET_MODE_SIZE (lhs_mode)))
>> >
>> > Is the FIX_TRUNC_EXPR case safe without some flag?
>> >
>> > #include <stdint.h>
>> > int32_t x = (int32_t)0x1.0p32;
>> > int32_t y = (int32_t)(int64_t)0x1.0p32;
>> >
>> > sets x to 2147483647 and y to 0.
>
> Hmm, good question.  GENERIC has a direct truncation to unsigned char
> for example, the C standard generally says if the integral part cannot
> be represented then the behavior is undefined.  So I think we should be
> safe here (0x1.0p32 doesn't fit an int).

OK.

>> Also, I think multi_step_cvt should influence the costs, since at
>> the moment we cost one statement but generate two.  This makes a
>> difference for SVE with VECT_COMPARE_COSTS.  Would changing it to:
>>
>>           vect_model_simple_cost (vinfo, stmt_info,
>>                                   ncopies * (multi_step_cvt + 1),
>>                                   dt, ndts, slp_node,
>>                                   cost_vec);
>>
>> be OK?
>
> Yeah, I guess so.

Thanks, will send a patch.

>> There again, I wonder if we should handle this using patterns instead.
>> That makes both conversions explicit and therefore easier to cost.
>
> But we don't do this for the other multi-step conversions either ...

Yeah, agree it's not a new problem.

> but sure, I also suggested that but the complaint was that with
> BB SLP this would get us a vector type with off lanes?

Ah, sorry, missed the previous discussion.  I only became interested
once some SVE tests started failing :)

>> E.g. for SVE, an integer extension is free if the source is a load,
>> and we do try to model that.  But it's difficult to handle if the
>> conversion is only implicit.
>
> In the distant future I hope that vectorizable_conversion will
> upon analysis produce an SLP sub-graph for the suggested
> code generation which we'd then cost.

Sounds good.  Agree we can live with the compound operation
until then.

> My current idea is
> to get this part live before switching the analysis to all-SLP
> because it "seems" easier (fingers crossing).  Still I'm
> struggling to even find time to start that effort.

Yeah, can sympthaise :/  Don't know how you find time for all
the reviews you currently do.

Thanks,
Richard

  reply	other threads:[~2023-06-21 11:20 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-06-02  1:00 liuhongt
2023-06-20  8:38 ` Richard Biener
2023-06-20  9:09   ` Hongtao Liu
2023-06-20  9:22     ` Richard Biener
2023-06-20 16:11       ` liuhongt
2023-06-21  7:49         ` Uros Bizjak
2023-06-21  8:19           ` Richard Biener
2023-06-21 14:37             ` Uros Bizjak
2023-06-22 20:36         ` Thiago Jung Bauermann
2023-06-21  9:10   ` Richard Sandiford
2023-06-21  9:32     ` Richard Sandiford
2023-06-21 11:04       ` Richard Biener
2023-06-21 11:20         ` Richard Sandiford [this message]
2023-06-21 20:39         ` Joseph Myers
2023-06-22  7:32           ` Richard Biener
2023-07-12  9:19             ` Robin Dapp

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