* [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483]
@ 2023-11-14 9:59 Xi Ruoyao
2023-11-14 10:44 ` Richard Biener
0 siblings, 1 reply; 4+ messages in thread
From: Xi Ruoyao @ 2023-11-14 9:59 UTC (permalink / raw)
To: gcc-patches
Cc: chenglulu, i, xuchenghua, Tamar Christina, tschwinge,
Roger Sayle, Andrew Pinski
From: Andrew Pinski <pinskia@gmail.com>
On targets with native copysign instructions, (copysign x, -1) is
usually more efficient than (fneg (fabs x)). Since r14-5284, in the
middle end we always optimize (fneg (fabs x)) to (copysign x, -1), not
vice versa. If the target does not support native fcopysign,
expand_COPYSIGN will expand it as (fneg (fabs x)) anyway.
gcc/ChangeLog:
PR rtl-optimization/112483
* simplify-rtx.cc (simplify_binary_operation_1) <case COPYSIGN>:
Call simplify_unary_operation for NEG instead of
simplify_gen_unary.
---
[xry111]:
Following Andrew's suggestion, I bootstrapped and regtested this
patch on loongarch64-linux-gnu. Now with
float t(float x)
{
return __builtin_copysignf(x, -0.1234);
}
It correctly generates
pcalau12i $r12,%pc_hi20(.LC0)
fld.s $f1,$r12,%pc_lo12(.LC0)
fcopysign.s $f0,$f0,$f1
jr $r1
instead of the de-optimized fabs.s and fneg.s
Ok for trunk?
gcc/simplify-rtx.cc | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 2d2e5a3c1ca..f3745d86aea 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -4392,7 +4392,7 @@ simplify_ashift:
real_convert (&f1, mode, CONST_DOUBLE_REAL_VALUE (trueop1));
rtx tmp = simplify_gen_unary (ABS, mode, op0, mode);
if (REAL_VALUE_NEGATIVE (f1))
- tmp = simplify_gen_unary (NEG, mode, tmp, mode);
+ tmp = simplify_unary_operation (NEG, mode, tmp, mode);
return tmp;
}
if (GET_CODE (op0) == NEG || GET_CODE (op0) == ABS)
--
2.42.1
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483]
2023-11-14 9:59 [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483] Xi Ruoyao
@ 2023-11-14 10:44 ` Richard Biener
2023-11-14 21:14 ` Xi Ruoyao
0 siblings, 1 reply; 4+ messages in thread
From: Richard Biener @ 2023-11-14 10:44 UTC (permalink / raw)
To: Xi Ruoyao
Cc: gcc-patches, chenglulu, i, xuchenghua, Tamar Christina,
tschwinge, Roger Sayle, Andrew Pinski
On Tue, Nov 14, 2023 at 11:04 AM Xi Ruoyao <xry111@xry111.site> wrote:
>
> From: Andrew Pinski <pinskia@gmail.com>
>
> On targets with native copysign instructions, (copysign x, -1) is
> usually more efficient than (fneg (fabs x)). Since r14-5284, in the
> middle end we always optimize (fneg (fabs x)) to (copysign x, -1), not
> vice versa. If the target does not support native fcopysign,
> expand_COPYSIGN will expand it as (fneg (fabs x)) anyway.
>
> gcc/ChangeLog:
>
> PR rtl-optimization/112483
> * simplify-rtx.cc (simplify_binary_operation_1) <case COPYSIGN>:
> Call simplify_unary_operation for NEG instead of
> simplify_gen_unary.
> ---
>
> [xry111]:
>
> Following Andrew's suggestion, I bootstrapped and regtested this
> patch on loongarch64-linux-gnu. Now with
>
> float t(float x)
> {
> return __builtin_copysignf(x, -0.1234);
> }
>
> It correctly generates
>
> pcalau12i $r12,%pc_hi20(.LC0)
> fld.s $f1,$r12,%pc_lo12(.LC0)
> fcopysign.s $f0,$f0,$f1
> jr $r1
>
> instead of the de-optimized fabs.s and fneg.s
>
> Ok for trunk?
>
> gcc/simplify-rtx.cc | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> index 2d2e5a3c1ca..f3745d86aea 100644
> --- a/gcc/simplify-rtx.cc
> +++ b/gcc/simplify-rtx.cc
> @@ -4392,7 +4392,7 @@ simplify_ashift:
> real_convert (&f1, mode, CONST_DOUBLE_REAL_VALUE (trueop1));
> rtx tmp = simplify_gen_unary (ABS, mode, op0, mode);
> if (REAL_VALUE_NEGATIVE (f1))
> - tmp = simplify_gen_unary (NEG, mode, tmp, mode);
> + tmp = simplify_unary_operation (NEG, mode, tmp, mode);
shouldn't that be when either the ABS or the NEG simplify? And I wonder
when that happens - I suppose when op0 is CONST_DOUBLE only?
> return tmp;
> }
> if (GET_CODE (op0) == NEG || GET_CODE (op0) == ABS)
> --
> 2.42.1
>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483]
2023-11-14 10:44 ` Richard Biener
@ 2023-11-14 21:14 ` Xi Ruoyao
2023-11-15 11:41 ` Richard Biener
0 siblings, 1 reply; 4+ messages in thread
From: Xi Ruoyao @ 2023-11-14 21:14 UTC (permalink / raw)
To: Richard Biener
Cc: gcc-patches, chenglulu, i, xuchenghua, Tamar Christina,
tschwinge, Roger Sayle, Andrew Pinski
On Tue, 2023-11-14 at 11:44 +0100, Richard Biener wrote:
> > diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> > index 2d2e5a3c1ca..f3745d86aea 100644
> > --- a/gcc/simplify-rtx.cc
> > +++ b/gcc/simplify-rtx.cc
> > @@ -4392,7 +4392,7 @@ simplify_ashift:
> > real_convert (&f1, mode, CONST_DOUBLE_REAL_VALUE (trueop1));
> > rtx tmp = simplify_gen_unary (ABS, mode, op0, mode);
> > if (REAL_VALUE_NEGATIVE (f1))
> > - tmp = simplify_gen_unary (NEG, mode, tmp, mode);
> > + tmp = simplify_unary_operation (NEG, mode, tmp, mode);
> > return tmp;
> > }
>
> shouldn't that be when either the ABS or the NEG simplify?
Simplify (copysign x, POSTIVE_CONST) to (abs x) is an optimization. So
for a positive f1, tmp will just be (abs x) and we return it.
> And I wonder when that happens - I suppose when op0 is CONST_DOUBLE only?
Yes, it's Andrew's intention.
--
Xi Ruoyao <xry111@xry111.site>
School of Aerospace Science and Technology, Xidian University
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483]
2023-11-14 21:14 ` Xi Ruoyao
@ 2023-11-15 11:41 ` Richard Biener
0 siblings, 0 replies; 4+ messages in thread
From: Richard Biener @ 2023-11-15 11:41 UTC (permalink / raw)
To: Xi Ruoyao
Cc: gcc-patches, chenglulu, i, xuchenghua, Tamar Christina,
tschwinge, Roger Sayle, Andrew Pinski
On Tue, Nov 14, 2023 at 10:14 PM Xi Ruoyao <xry111@xry111.site> wrote:
>
> On Tue, 2023-11-14 at 11:44 +0100, Richard Biener wrote:
> > > diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
> > > index 2d2e5a3c1ca..f3745d86aea 100644
> > > --- a/gcc/simplify-rtx.cc
> > > +++ b/gcc/simplify-rtx.cc
> > > @@ -4392,7 +4392,7 @@ simplify_ashift:
> > > real_convert (&f1, mode, CONST_DOUBLE_REAL_VALUE (trueop1));
> > > rtx tmp = simplify_gen_unary (ABS, mode, op0, mode);
> > > if (REAL_VALUE_NEGATIVE (f1))
> > > - tmp = simplify_gen_unary (NEG, mode, tmp, mode);
> > > + tmp = simplify_unary_operation (NEG, mode, tmp, mode);
> > > return tmp;
> > > }
> >
> > shouldn't that be when either the ABS or the NEG simplify?
>
> Simplify (copysign x, POSTIVE_CONST) to (abs x) is an optimization. So
> for a positive f1, tmp will just be (abs x) and we return it.
Ah, OK.
> > And I wonder when that happens - I suppose when op0 is CONST_DOUBLE only?
>
> Yes, it's Andrew's intention.
The patch is fine then.
Richard.
> --
> Xi Ruoyao <xry111@xry111.site>
> School of Aerospace Science and Technology, Xidian University
^ permalink raw reply [flat|nested] 4+ messages in thread
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2023-11-14 9:59 [PATCH] Only allow (copysign x, NEG_CONST) -> (fneg (fabs x)) simplification for constant folding [PR112483] Xi Ruoyao
2023-11-14 10:44 ` Richard Biener
2023-11-14 21:14 ` Xi Ruoyao
2023-11-15 11:41 ` Richard Biener
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