Hi Prathamesh,

Yes Arm requires SIMD for copysign. The testcases fail because they don't turn on Neon.

I'll update them.

Regards,
Tamar
________________________________
From: Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>
Sent: Friday, November 10, 2023 12:24 PM
To: Tamar Christina <Tamar.Christina@arm.com>
Cc: gcc-patches@gcc.gnu.org <gcc-patches@gcc.gnu.org>; nd <nd@arm.com>; rguenther@suse.de <rguenther@suse.de>; jlaw@ventanamicro.com <jlaw@ventanamicro.com>
Subject: Re: [PATCH v3 2/2]middle-end match.pd: optimize fneg (fabs (x)) to copysign (x, -1) [PR109154]

On Mon, 6 Nov 2023 at 15:50, Tamar Christina <tamar.christina@arm.com> wrote:
>
> Hi All,
>
> This patch transforms fneg (fabs (x)) into copysign (x, -1) which is more
> canonical and allows a target to expand this sequence efficiently.  Such
> sequences are common in scientific code working with gradients.
>
> There is an existing canonicalization of copysign (x, -1) to fneg (fabs (x))
> which I remove since this is a less efficient form.  The testsuite is also
> updated in light of this.
>
> Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.
Hi Tamar,
It seems the patch caused following regressions on arm:

Running gcc:gcc.dg/dg.exp ...
FAIL: gcc.dg/pr55152-2.c scan-tree-dump-times optimized ".COPYSIGN" 1
FAIL: gcc.dg/pr55152-2.c scan-tree-dump-times optimized "ABS_EXPR" 1

Running gcc:gcc.dg/tree-ssa/tree-ssa.exp ...
FAIL: gcc.dg/tree-ssa/abs-4.c scan-tree-dump-times optimized "= -" 1
FAIL: gcc.dg/tree-ssa/abs-4.c scan-tree-dump-times optimized "= .COPYSIGN" 2
FAIL: gcc.dg/tree-ssa/abs-4.c scan-tree-dump-times optimized "= ABS_EXPR" 1
FAIL: gcc.dg/tree-ssa/backprop-6.c scan-tree-dump-times backprop
"Deleting[^\\n]* = -" 4
FAIL: gcc.dg/tree-ssa/backprop-6.c scan-tree-dump-times backprop
"Deleting[^\\n]* = ABS_EXPR <" 1
FAIL: gcc.dg/tree-ssa/backprop-6.c scan-tree-dump-times backprop
"Deleting[^\\n]* = \\.COPYSIGN" 2
FAIL: gcc.dg/tree-ssa/copy-sign-2.c scan-tree-dump-times optimized ".COPYSIGN" 1
FAIL: gcc.dg/tree-ssa/copy-sign-2.c scan-tree-dump-times optimized "ABS" 1
FAIL: gcc.dg/tree-ssa/mult-abs-2.c scan-tree-dump-times gimple ".COPYSIGN" 4
FAIL: gcc.dg/tree-ssa/mult-abs-2.c scan-tree-dump-times gimple "ABS" 4
FAIL: gcc.dg/tree-ssa/phi-opt-24.c scan-tree-dump-not phiopt2 "if"
Link to log files:
https://ci.linaro.org/job/tcwg_gcc_check--master-arm-build/1240/artifact/artifacts/00-sumfiles/

Even for following test-case:
double g (double a)
{
  double t1 = fabs (a);
  double t2 = -t1;
  return t2;
}

It seems, the pattern gets applied but doesn't get eventually
simplified to copysign(a, -1).
forwprop dump shows:
Applying pattern match.pd:1131, gimple-match-4.cc:4134
double g (double a)
{
  double t2;
  double t1;

  <bb 2> :
  t1_2 = ABS_EXPR <a_1(D)>;
  t2_3 = -t1_2;
  return t2_3;

}

while on x86_64:
Applying pattern match.pd:1131, gimple-match-4.cc:4134
gimple_simplified to t2_3 = .COPYSIGN (a_1(D), -1.0e+0);
Removing dead stmt:t1_2 = ABS_EXPR <a_1(D)>;
double g (double a)
{
  double t2;
  double t1;

  <bb 2> :
  t2_3 = .COPYSIGN (a_1(D), -1.0e+0);
  return t2_3;

}

Thanks,
Prathamesh


>
> Ok for master?
>
> Thanks,
> Tamar
>
> gcc/ChangeLog:
>
>         PR tree-optimization/109154
>         * match.pd: Add new neg+abs rule, remove inverse copysign rule.
>
> gcc/testsuite/ChangeLog:
>
>         PR tree-optimization/109154
>         * gcc.dg/fold-copysign-1.c: Updated.
>         * gcc.dg/pr55152-2.c: Updated.
>         * gcc.dg/tree-ssa/abs-4.c: Updated.
>         * gcc.dg/tree-ssa/backprop-6.c: Updated.
>         * gcc.dg/tree-ssa/copy-sign-2.c: Updated.
>         * gcc.dg/tree-ssa/mult-abs-2.c: Updated.
>         * gcc.target/aarch64/fneg-abs_1.c: New test.
>         * gcc.target/aarch64/fneg-abs_2.c: New test.
>         * gcc.target/aarch64/fneg-abs_3.c: New test.
>         * gcc.target/aarch64/fneg-abs_4.c: New test.
>         * gcc.target/aarch64/sve/fneg-abs_1.c: New test.
>         * gcc.target/aarch64/sve/fneg-abs_2.c: New test.
>         * gcc.target/aarch64/sve/fneg-abs_3.c: New test.
>         * gcc.target/aarch64/sve/fneg-abs_4.c: New test.
>
> --- inline copy of patch --
> diff --git a/gcc/match.pd b/gcc/match.pd
> index db95931df0672cf4ef08cca36085c3aa6831519e..7a023d510c283c43a87b1795a74761b8af979b53 100644
> --- a/gcc/match.pd
> +++ b/gcc/match.pd
> @@ -1106,13 +1106,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
>     (hypots @0 (copysigns @1 @2))
>     (hypots @0 @1))))
>
> -/* copysign(x, CST) -> [-]abs (x).  */
> -(for copysigns (COPYSIGN_ALL)
> - (simplify
> -  (copysigns @0 REAL_CST@1)
> -  (if (REAL_VALUE_NEGATIVE (TREE_REAL_CST (@1)))
> -   (negate (abs @0))
> -   (abs @0))))
> +/* Transform fneg (fabs (X)) -> copysign (X, -1).  */
> +
> +(simplify
> + (negate (abs @0))
> + (IFN_COPYSIGN @0 { build_minus_one_cst (type); }))
>
>  /* copysign(copysign(x, y), z) -> copysign(x, z).  */
>  (for copysigns (COPYSIGN_ALL)
> diff --git a/gcc/testsuite/gcc.dg/fold-copysign-1.c b/gcc/testsuite/gcc.dg/fold-copysign-1.c
> index f17d65c24ee4dca9867827d040fe0a404c515e7b..f9cafd14ab05f5e8ab2f6f68e62801d21c2df6a6 100644
> --- a/gcc/testsuite/gcc.dg/fold-copysign-1.c
> +++ b/gcc/testsuite/gcc.dg/fold-copysign-1.c
> @@ -12,5 +12,5 @@ double bar (double x)
>    return __builtin_copysign (x, minuszero);
>  }
>
> -/* { dg-final { scan-tree-dump-times "= -" 1 "cddce1" } } */
> -/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 2 "cddce1" } } */
> +/* { dg-final { scan-tree-dump-times "__builtin_copysign" 1 "cddce1" } } */
> +/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 1 "cddce1" } } */
> diff --git a/gcc/testsuite/gcc.dg/pr55152-2.c b/gcc/testsuite/gcc.dg/pr55152-2.c
> index 54db0f2062da105a829d6690ac8ed9891fe2b588..605f202ed6bc7aa8fe921457b02ff0b88cc63ce6 100644
> --- a/gcc/testsuite/gcc.dg/pr55152-2.c
> +++ b/gcc/testsuite/gcc.dg/pr55152-2.c
> @@ -10,4 +10,5 @@ int f(int a)
>    return (a<-a)?a:-a;
>  }
>
> -/* { dg-final { scan-tree-dump-times "ABS_EXPR" 2 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "\.COPYSIGN" 1 "optimized" } } */
> +/* { dg-final { scan-tree-dump-times "ABS_EXPR" 1 "optimized" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c b/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
> index 6197519faf7b55aed7bc162cd0a14dd2145210ca..e1b825f37f69ac3c4666b3a52d733368805ad31d 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/abs-4.c
> @@ -9,5 +9,6 @@ long double abs_ld(long double x) { return __builtin_signbit(x) ? x : -x; }
>
>  /* __builtin_signbit(x) ? x : -x. Should be convert into - ABS_EXP<x> */
>  /* { dg-final { scan-tree-dump-not "signbit" "optimized"} } */
> -/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 3 "optimized"} } */
> -/* { dg-final { scan-tree-dump-times "= -" 3 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times "= ABS_EXPR" 1 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times "= -" 1 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times "= \.COPYSIGN" 2 "optimized"} } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/backprop-6.c b/gcc/testsuite/gcc.dg/tree-ssa/backprop-6.c
> index 31f05716f1498dc709cac95fa20fb5796642c77e..c3a138642d6ff7be984e91fa1343cb2718db7ae1 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/backprop-6.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/backprop-6.c
> @@ -26,5 +26,6 @@ TEST_FUNCTION (float, f)
>  TEST_FUNCTION (double, )
>  TEST_FUNCTION (long double, l)
>
> -/* { dg-final { scan-tree-dump-times {Deleting[^\n]* = -} 6 "backprop" } } */
> -/* { dg-final { scan-tree-dump-times {Deleting[^\n]* = ABS_EXPR <} 3 "backprop" } } */
> +/* { dg-final { scan-tree-dump-times {Deleting[^\n]* = -} 4 "backprop" } } */
> +/* { dg-final { scan-tree-dump-times {Deleting[^\n]* = \.COPYSIGN} 2 "backprop" } } */
> +/* { dg-final { scan-tree-dump-times {Deleting[^\n]* = ABS_EXPR <} 1 "backprop" } } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/copy-sign-2.c b/gcc/testsuite/gcc.dg/tree-ssa/copy-sign-2.c
> index de52c5f7c8062958353d91f5031193defc9f3f91..e5d565c4b9832c00106588ef411fbd8c292a5cad 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/copy-sign-2.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/copy-sign-2.c
> @@ -10,4 +10,5 @@ float f1(float x)
>    float t = __builtin_copysignf (1.0f, -x);
>    return x * t;
>  }
> -/* { dg-final { scan-tree-dump-times "ABS" 2 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times "ABS" 1 "optimized"} } */
> +/* { dg-final { scan-tree-dump-times ".COPYSIGN" 1 "optimized"} } */
> diff --git a/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-2.c b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-2.c
> index a41f1baf25669a4fd301a586a49ba5e3c5b966ab..a22896b21c8b5a4d5d8e28bd8ae0db896e63ade0 100644
> --- a/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-2.c
> +++ b/gcc/testsuite/gcc.dg/tree-ssa/mult-abs-2.c
> @@ -34,4 +34,5 @@ float i1(float x)
>  {
>    return x * (x <= 0.f ? 1.f : -1.f);
>  }
> -/* { dg-final { scan-tree-dump-times "ABS" 8 "gimple"} } */
> +/* { dg-final { scan-tree-dump-times "ABS" 4 "gimple"} } */
> +/* { dg-final { scan-tree-dump-times "\.COPYSIGN" 4 "gimple"} } */
> diff --git a/gcc/testsuite/gcc.target/aarch64/fneg-abs_1.c b/gcc/testsuite/gcc.target/aarch64/fneg-abs_1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..f823013c3ddf6b3a266c3abfcbf2642fc2a75fa6
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/fneg-abs_1.c
> @@ -0,0 +1,39 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#pragma GCC target "+nosve"
> +
> +#include <arm_neon.h>
> +
> +/*
> +** t1:
> +**     orr     v[0-9]+.2s, #128, lsl #24
> +**     ret
> +*/
> +float32x2_t t1 (float32x2_t a)
> +{
> +  return vneg_f32 (vabs_f32 (a));
> +}
> +
> +/*
> +** t2:
> +**     orr     v[0-9]+.4s, #128, lsl #24
> +**     ret
> +*/
> +float32x4_t t2 (float32x4_t a)
> +{
> +  return vnegq_f32 (vabsq_f32 (a));
> +}
> +
> +/*
> +** t3:
> +**     adrp    x0, .LC[0-9]+
> +**     ldr     q[0-9]+, \[x0, #:lo12:.LC0\]
> +**     orr     v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
> +**     ret
> +*/
> +float64x2_t t3 (float64x2_t a)
> +{
> +  return vnegq_f64 (vabsq_f64 (a));
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/fneg-abs_2.c b/gcc/testsuite/gcc.target/aarch64/fneg-abs_2.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..141121176b309e4b2aa413dc55271a6e3c93d5e1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/fneg-abs_2.c
> @@ -0,0 +1,31 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#pragma GCC target "+nosve"
> +
> +#include <arm_neon.h>
> +#include <math.h>
> +
> +/*
> +** f1:
> +**     movi    v[0-9]+.2s, 0x80, lsl 24
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float32_t f1 (float32_t a)
> +{
> +  return -fabsf (a);
> +}
> +
> +/*
> +** f2:
> +**     mov     x0, -9223372036854775808
> +**     fmov    d[0-9]+, x0
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float64_t f2 (float64_t a)
> +{
> +  return -fabs (a);
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/fneg-abs_3.c b/gcc/testsuite/gcc.target/aarch64/fneg-abs_3.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..b4652173a95d104ddfa70c497f0627a61ea89d3b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/fneg-abs_3.c
> @@ -0,0 +1,36 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#pragma GCC target "+nosve"
> +
> +#include <arm_neon.h>
> +#include <math.h>
> +
> +/*
> +** f1:
> +**     ...
> +**     ldr     q[0-9]+, \[x0\]
> +**     orr     v[0-9]+.4s, #128, lsl #24
> +**     str     q[0-9]+, \[x0\], 16
> +**     ...
> +*/
> +void f1 (float32_t *a, int n)
> +{
> +  for (int i = 0; i < (n & -8); i++)
> +   a[i] = -fabsf (a[i]);
> +}
> +
> +/*
> +** f2:
> +**     ...
> +**     ldr     q[0-9]+, \[x0\]
> +**     orr     v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
> +**     str     q[0-9]+, \[x0\], 16
> +**     ...
> +*/
> +void f2 (float64_t *a, int n)
> +{
> +  for (int i = 0; i < (n & -8); i++)
> +   a[i] = -fabs (a[i]);
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/fneg-abs_4.c b/gcc/testsuite/gcc.target/aarch64/fneg-abs_4.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..10879dea74462d34b26160eeb0bd54ead063166b
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/fneg-abs_4.c
> @@ -0,0 +1,39 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#pragma GCC target "+nosve"
> +
> +#include <string.h>
> +
> +/*
> +** negabs:
> +**     mov     x0, -9223372036854775808
> +**     fmov    d[0-9]+, x0
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +double negabs (double x)
> +{
> +   unsigned long long y;
> +   memcpy (&y, &x, sizeof(double));
> +   y = y | (1UL << 63);
> +   memcpy (&x, &y, sizeof(double));
> +   return x;
> +}
> +
> +/*
> +** negabsf:
> +**     movi    v[0-9]+.2s, 0x80, lsl 24
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float negabsf (float x)
> +{
> +   unsigned int y;
> +   memcpy (&y, &x, sizeof(float));
> +   y = y | (1U << 31);
> +   memcpy (&x, &y, sizeof(float));
> +   return x;
> +}
> +
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_1.c b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_1.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..0c7664e6de77a497682952653ffd417453854d52
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_1.c
> @@ -0,0 +1,37 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#include <arm_neon.h>
> +
> +/*
> +** t1:
> +**     orr     v[0-9]+.2s, #128, lsl #24
> +**     ret
> +*/
> +float32x2_t t1 (float32x2_t a)
> +{
> +  return vneg_f32 (vabs_f32 (a));
> +}
> +
> +/*
> +** t2:
> +**     orr     v[0-9]+.4s, #128, lsl #24
> +**     ret
> +*/
> +float32x4_t t2 (float32x4_t a)
> +{
> +  return vnegq_f32 (vabsq_f32 (a));
> +}
> +
> +/*
> +** t3:
> +**     adrp    x0, .LC[0-9]+
> +**     ldr     q[0-9]+, \[x0, #:lo12:.LC0\]
> +**     orr     v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
> +**     ret
> +*/
> +float64x2_t t3 (float64x2_t a)
> +{
> +  return vnegq_f64 (vabsq_f64 (a));
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_2.c b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_2.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..a60cd31b9294af2dac69eed1c93f899bd5c78fca
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_2.c
> @@ -0,0 +1,29 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#include <arm_neon.h>
> +#include <math.h>
> +
> +/*
> +** f1:
> +**     movi    v[0-9]+.2s, 0x80, lsl 24
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float32_t f1 (float32_t a)
> +{
> +  return -fabsf (a);
> +}
> +
> +/*
> +** f2:
> +**     mov     x0, -9223372036854775808
> +**     fmov    d[0-9]+, x0
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float64_t f2 (float64_t a)
> +{
> +  return -fabs (a);
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_3.c b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_3.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..1bf34328d8841de8e6b0a5458562a9f00e31c275
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_3.c
> @@ -0,0 +1,34 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#include <arm_neon.h>
> +#include <math.h>
> +
> +/*
> +** f1:
> +**     ...
> +**     ld1w    z[0-9]+.s, p[0-9]+/z, \[x0, x2, lsl 2\]
> +**     orr     z[0-9]+.s, z[0-9]+.s, #0x80000000
> +**     st1w    z[0-9]+.s, p[0-9]+, \[x0, x2, lsl 2\]
> +**     ...
> +*/
> +void f1 (float32_t *a, int n)
> +{
> +  for (int i = 0; i < (n & -8); i++)
> +   a[i] = -fabsf (a[i]);
> +}
> +
> +/*
> +** f2:
> +**     ...
> +**     ld1d    z[0-9]+.d, p[0-9]+/z, \[x0, x2, lsl 3\]
> +**     orr     z[0-9]+.d, z[0-9]+.d, #0x8000000000000000
> +**     st1d    z[0-9]+.d, p[0-9]+, \[x0, x2, lsl 3\]
> +**     ...
> +*/
> +void f2 (float64_t *a, int n)
> +{
> +  for (int i = 0; i < (n & -8); i++)
> +   a[i] = -fabs (a[i]);
> +}
> diff --git a/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_4.c b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_4.c
> new file mode 100644
> index 0000000000000000000000000000000000000000..21f2a8da2a5d44e3d01f6604ca7be87e3744d494
> --- /dev/null
> +++ b/gcc/testsuite/gcc.target/aarch64/sve/fneg-abs_4.c
> @@ -0,0 +1,37 @@
> +/* { dg-do compile } */
> +/* { dg-options "-O3" } */
> +/* { dg-final { check-function-bodies "**" "" "" { target lp64 } } } */
> +
> +#include <string.h>
> +
> +/*
> +** negabs:
> +**     mov     x0, -9223372036854775808
> +**     fmov    d[0-9]+, x0
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +double negabs (double x)
> +{
> +   unsigned long long y;
> +   memcpy (&y, &x, sizeof(double));
> +   y = y | (1UL << 63);
> +   memcpy (&x, &y, sizeof(double));
> +   return x;
> +}
> +
> +/*
> +** negabsf:
> +**     movi    v[0-9]+.2s, 0x80, lsl 24
> +**     orr     v[0-9]+.8b, v[0-9]+.8b, v[0-9]+.8b
> +**     ret
> +*/
> +float negabsf (float x)
> +{
> +   unsigned int y;
> +   memcpy (&y, &x, sizeof(float));
> +   y = y | (1U << 31);
> +   memcpy (&x, &y, sizeof(float));
> +   return x;
> +}
> +
>
>
>
>
> --