> -----Original Message-----
> From: Richard Sandiford <richard.sandif...@arm.com>
> Sent: Tuesday, November 1, 2022 3:05 PM
> To: Tamar Christina <tamar.christ...@arm.com>
> Cc: gcc-patches@gcc.gnu.org; nd <n...@arm.com>; Richard Earnshaw
> <richard.earns...@arm.com>; Marcus Shawcroft
> <marcus.shawcr...@arm.com>; Kyrylo Tkachov <kyrylo.tkac...@arm.com>
> Subject: Re: [PATCH 8/8]AArch64: Have reload not choose to do add on the
> scalar side if both values exist on the SIMD side.
>
> Tamar Christina <tamar.christ...@arm.com> writes:
> > Hi All,
> >
> > Currently we often times generate an r -> r add even if it means we
> > need two reloads to perform it, i.e. in the case that the values are on the
> SIMD side.
> >
> > The pairwise operations expose these more now and so we get suboptimal
> codegen.
> >
> > Normally I would have liked to use ^ or $ here, but while this works
> > for the simple examples, reload inexplicably falls apart on examples
> > that should have been trivial. It forces a move to r -> w to use the w
> > ADD, which is counter to what ^ and $ should do.
> >
> > However ! seems to fix all the regression and still maintains the good
> codegen.
> >
> > I have tried looking into whether it's our costings that are off, but
> > I can't seem anything logical here. So I'd like to push this change
> > instead along with test that augment the other testcases that guard the r ->
> r variants.
>
> This feels like a hack though. r<-r+r is one of the simplest thing the
> processor
> can do, so I don't think it makes logical sense to mark it with !, which means
> "prohibitively expensive". It's likely to push operations that require
> reloads
> onto the SIMD side.
I agree. Though at the moment, reload isn't behaving as it should. It's almost
as if
the register transfer costs are not taken into account when deciding on an
alternative.
It seems to think that an r->r and w->w are as cheap even when the value has
been assigned
to w before. For instance, some of the testcases below don't work correctly
because of this.
I don't think I can influence this costing, and as I mentioned ^ works for the
simple example
But then somehow makes w->w cheaper even though the value was assigned to r.
I'm not really sure where to look here, but the current version is also equally
broken..
It basically always forces to r.
Thanks,
Tamar
>
> Thanks,
> Richard
>
> > Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
> >
> > Ok for master?
> >
> > Thanks,
> > Tamar
> >
> > gcc/ChangeLog:
> >
> > * config/aarch64/aarch64.md (*add<mode>3_aarch64): Add ! to the
> r -> r
> > alternative.
> >
> > gcc/testsuite/ChangeLog:
> >
> > * gcc.target/aarch64/simd/scalar_addp.c: New test.
> > * gcc.target/aarch64/simd/scalar_faddp.c: New test.
> > * gcc.target/aarch64/simd/scalar_faddp2.c: New test.
> > * gcc.target/aarch64/simd/scalar_fmaxp.c: New test.
> > * gcc.target/aarch64/simd/scalar_fminp.c: New test.
> > * gcc.target/aarch64/simd/scalar_maxp.c: New test.
> > * gcc.target/aarch64/simd/scalar_minp.c: New test.
> >
> > --- inline copy of patch --
> > diff --git a/gcc/config/aarch64/aarch64.md
> > b/gcc/config/aarch64/aarch64.md index
> >
> 09ae1118371f82ca63146fceb953eb9e820d05a4..c333fb1f72725992bb304c560f
> 12
> > 45a242d5192d 100644
> > --- a/gcc/config/aarch64/aarch64.md
> > +++ b/gcc/config/aarch64/aarch64.md
> > @@ -2043,7 +2043,7 @@ (define_expand "add<mode>3"
> >
> > (define_insn "*add<mode>3_aarch64"
> > [(set
> > - (match_operand:GPI 0 "register_operand" "=rk,rk,w,rk,r,r,rk")
> > + (match_operand:GPI 0 "register_operand" "=rk,!rk,w,rk,r,r,rk")
> > (plus:GPI
> > (match_operand:GPI 1 "register_operand" "%rk,rk,w,rk,rk,0,rk")
> > (match_operand:GPI 2 "aarch64_pluslong_operand"
> > "I,r,w,J,Uaa,Uai,Uav")))] diff --git
> > a/gcc/testsuite/gcc.target/aarch64/simd/scalar_addp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_addp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..5b8d40f19884fc7b4e7decd80
> 758
> > bc36fa76d058
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_addp.c
> > @@ -0,0 +1,70 @@
> > +/* { dg-do assemble } */
> > +/* { dg-additional-options "-save-temps -O1 -std=c99" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef long long v2di __attribute__((vector_size (16))); typedef
> > +unsigned long long v2udi __attribute__((vector_size (16))); typedef
> > +int v2si __attribute__((vector_size (16))); typedef unsigned int
> > +v2usi __attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** addp d0, v0.2d
> > +** fmov x0, d0
> > +** ret
> > +*/
> > +long long
> > +foo (v2di x)
> > +{
> > + return x[1] + x[0];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** saddlp v0.1d, v0.2s
> > +** fmov x0, d0
> > +** ret
> > +*/
> > +long long
> > +foo1 (v2si x)
> > +{
> > + return x[1] + x[0];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** uaddlp v0.1d, v0.2s
> > +** fmov x0, d0
> > +** ret
> > +*/
> > +unsigned long long
> > +foo2 (v2usi x)
> > +{
> > + return x[1] + x[0];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** uaddlp v0.1d, v0.2s
> > +** add d0, d0, d1
> > +** fmov x0, d0
> > +** ret
> > +*/
> > +unsigned long long
> > +foo3 (v2usi x, v2udi y)
> > +{
> > + return (x[1] + x[0]) + y[0];
> > +}
> > +
> > +/*
> > +** foo4:
> > +** saddlp v0.1d, v0.2s
> > +** add d0, d0, d1
> > +** fmov x0, d0
> > +** ret
> > +*/
> > +long long
> > +foo4 (v2si x, v2di y)
> > +{
> > + return (x[1] + x[0]) + y[0];
> > +}
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..ff455e060fc833b2f63e89c467
> b9
> > 1a76fbe31aff
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp.c
> > @@ -0,0 +1,66 @@
> > +/* { dg-do assemble } */
> > +/* { dg-require-effective-target arm_v8_2a_fp16_scalar_ok } */
> > +/* { dg-add-options arm_v8_2a_fp16_scalar } */
> > +/* { dg-additional-options "-save-temps -O1" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef double v2df __attribute__((vector_size (16))); typedef float
> > +v4sf __attribute__((vector_size (16))); typedef __fp16 v8hf
> > +__attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** faddp d0, v0.2d
> > +** ret
> > +*/
> > +double
> > +foo (v2df x)
> > +{
> > + return x[1] + x[0];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** faddp s0, v0.2s
> > +** ret
> > +*/
> > +float
> > +foo1 (v4sf x)
> > +{
> > + return x[0] + x[1];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** faddp h0, v0.2h
> > +** ret
> > +*/
> > +__fp16
> > +foo2 (v8hf x)
> > +{
> > + return x[0] + x[1];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** ext v0.16b, v0.16b, v0.16b, #4
> > +** faddp s0, v0.2s
> > +** ret
> > +*/
> > +float
> > +foo3 (v4sf x)
> > +{
> > + return x[1] + x[2];
> > +}
> > +
> > +/*
> > +** foo4:
> > +** dup s0, v0.s\[3\]
> > +** faddp h0, v0.2h
> > +** ret
> > +*/
> > +__fp16
> > +foo4 (v8hf x)
> > +{
> > + return x[6] + x[7];
> > +}
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp2.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp2.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..04412c3b45c51648e46ff20f73
> 0b
> > 1213e940391a
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_faddp2.c
> > @@ -0,0 +1,14 @@
> > +/* { dg-do assemble } */
> > +/* { dg-additional-options "-save-temps -O1 -w" } */
> > +
> > +typedef __m128i __attribute__((__vector_size__(2 * sizeof(long))));
> > +double a[]; *b;
> > +fn1() {
> > + __m128i c;
> > + *(__m128i *)a = c;
> > + *b = a[0] + a[1];
> > +}
> > +
> > +/* { dg-final { scan-assembler-times {faddp\td0, v0\.2d} 1 } } */
> > +
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_fmaxp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_fmaxp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..aa1d2bf17cd707b74d8f7c5745
> 06
> > 610ab4fd7299
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_fmaxp.c
> > @@ -0,0 +1,56 @@
> > +/* { dg-do assemble } */
> > +/* { dg-require-effective-target arm_v8_2a_fp16_scalar_ok } */
> > +/* { dg-add-options arm_v8_2a_fp16_scalar } */
> > +/* { dg-additional-options "-save-temps -O1" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef double v2df __attribute__((vector_size (16))); typedef float
> > +v4sf __attribute__((vector_size (16))); typedef __fp16 v8hf
> > +__attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** fmaxnmp d0, v0.2d
> > +** ret
> > +*/
> > +double
> > +foo (v2df x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** fmaxnmp s0, v0.2s
> > +** ret
> > +*/
> > +float
> > +foo1 (v4sf x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** fmaxnmp h0, v0.2h
> > +** ret
> > +*/
> > +__fp16
> > +foo2 (v8hf x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** fmaxnmp s0, v0.2s
> > +** fcvt d0, s0
> > +** fadd d0, d0, d1
> > +** ret
> > +*/
> > +double
> > +foo3 (v4sf x, v2df y)
> > +{
> > + return (x[0] > x[1] ? x[0] : x[1]) + y[0]; }
> > +
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_fminp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_fminp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..6136c5272069c4d86f09951cdff
> 2
> > 5f1494e839f0
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_fminp.c
> > @@ -0,0 +1,55 @@
> > +/* { dg-do assemble } */
> > +/* { dg-require-effective-target arm_v8_2a_fp16_scalar_ok } */
> > +/* { dg-add-options arm_v8_2a_fp16_scalar } */
> > +/* { dg-additional-options "-save-temps -O1" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef double v2df __attribute__((vector_size (16))); typedef float
> > +v4sf __attribute__((vector_size (16))); typedef __fp16 v8hf
> > +__attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** fminnmp d0, v0.2d
> > +** ret
> > +*/
> > +double
> > +foo (v2df x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** fminnmp s0, v0.2s
> > +** ret
> > +*/
> > +float
> > +foo1 (v4sf x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** fminnmp h0, v0.2h
> > +** ret
> > +*/
> > +__fp16
> > +foo2 (v8hf x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** fminnmp s0, v0.2s
> > +** fcvt d0, s0
> > +** fadd d0, d0, d1
> > +** ret
> > +*/
> > +double
> > +foo3 (v4sf x, v2df y)
> > +{
> > + return (x[0] < x[1] ? x[0] : x[1]) + y[0]; }
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_maxp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_maxp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..e219a13abc745b83dca58633f
> d2d
> > 812e276d6b2d
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_maxp.c
> > @@ -0,0 +1,74 @@
> > +/* { dg-do assemble } */
> > +/* { dg-additional-options "-save-temps -O1 -std=c99" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef long long v2di __attribute__((vector_size (16))); typedef
> > +unsigned long long v2udi __attribute__((vector_size (16))); typedef
> > +int v2si __attribute__((vector_size (16))); typedef unsigned int
> > +v2usi __attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** umov x0, v0.d\[1\]
> > +** fmov x1, d0
> > +** cmp x0, x1
> > +** csel x0, x0, x1, ge
> > +** ret
> > +*/
> > +long long
> > +foo (v2di x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** smaxp v0.2s, v0.2s, v0.2s
> > +** smov x0, v0.s\[0\]
> > +** ret
> > +*/
> > +long long
> > +foo1 (v2si x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** umaxp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** ret
> > +*/
> > +unsigned long long
> > +foo2 (v2usi x)
> > +{
> > + return x[0] > x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** umaxp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** fmov x1, d1
> > +** add x0, x1, w0, uxtw
> > +** ret
> > +*/
> > +unsigned long long
> > +foo3 (v2usi x, v2udi y)
> > +{
> > + return (x[0] > x[1] ? x[0] : x[1]) + y[0]; }
> > +
> > +/*
> > +** foo4:
> > +** smaxp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** fmov x1, d1
> > +** add x0, x1, w0, sxtw
> > +** ret
> > +*/
> > +long long
> > +foo4 (v2si x, v2di y)
> > +{
> > + return (x[0] > x[1] ? x[0] : x[1]) + y[0]; }
> > diff --git a/gcc/testsuite/gcc.target/aarch64/simd/scalar_minp.c
> > b/gcc/testsuite/gcc.target/aarch64/simd/scalar_minp.c
> > new file mode 100644
> > index
> >
> 0000000000000000000000000000000000000000..2a32fb4ea3edaa4c547a7a481c
> 3d
> > dca6b477430e
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.target/aarch64/simd/scalar_minp.c
> > @@ -0,0 +1,74 @@
> > +/* { dg-do assemble } */
> > +/* { dg-additional-options "-save-temps -O1 -std=c99" } */
> > +/* { dg-final { check-function-bodies "**" "" "" { target { le } } }
> > +} */
> > +
> > +typedef long long v2di __attribute__((vector_size (16))); typedef
> > +unsigned long long v2udi __attribute__((vector_size (16))); typedef
> > +int v2si __attribute__((vector_size (16))); typedef unsigned int
> > +v2usi __attribute__((vector_size (16)));
> > +
> > +/*
> > +** foo:
> > +** umov x0, v0.d\[1\]
> > +** fmov x1, d0
> > +** cmp x0, x1
> > +** csel x0, x0, x1, le
> > +** ret
> > +*/
> > +long long
> > +foo (v2di x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo1:
> > +** sminp v0.2s, v0.2s, v0.2s
> > +** smov x0, v0.s\[0\]
> > +** ret
> > +*/
> > +long long
> > +foo1 (v2si x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo2:
> > +** uminp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** ret
> > +*/
> > +unsigned long long
> > +foo2 (v2usi x)
> > +{
> > + return x[0] < x[1] ? x[0] : x[1];
> > +}
> > +
> > +/*
> > +** foo3:
> > +** uminp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** fmov x1, d1
> > +** add x0, x1, w0, uxtw
> > +** ret
> > +*/
> > +unsigned long long
> > +foo3 (v2usi x, v2udi y)
> > +{
> > + return (x[0] < x[1] ? x[0] : x[1]) + y[0]; }
> > +
> > +/*
> > +** foo4:
> > +** sminp v0.2s, v0.2s, v0.2s
> > +** fmov w0, s0
> > +** fmov x1, d1
> > +** add x0, x1, w0, sxtw
> > +** ret
> > +*/
> > +long long
> > +foo4 (v2si x, v2di y)
> > +{
> > + return (x[0] < x[1] ? x[0] : x[1]) + y[0]; }
