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AArch64: Implement widen_[us]sum using dotproduct for SVE [PR122069] 

This patch implements support for using dotproduct to do sum reductions by
changing += a into += (a * 1).  i.e. we seed the multiplication with 1.

Given the example

int foo_int(unsigned char *x, unsigned char * restrict y) {
  int sum = 0;
  for (int i = 0; i < 8000; i++)
     sum += char_abs(x[i] - y[i]);
  return sum;
}

we used to generate

.L2:
        ld1b    z1.b, p7/z, [x0, x2]
        ld1b    z29.b, p7/z, [x1, x2]
        sub     z29.b, z1.b, z29.b
        uunpklo z0.h, z29.b
        uunpkhi z29.h, z29.b
        uunpklo z30.s, z0.h
        add     z31.s, p6/m, z31.s, z30.s
        uunpkhi z0.s, z0.h
        add     z31.s, p5/m, z31.s, z0.s
        uunpklo z28.s, z29.h
        add     z31.s, p4/m, z31.s, z28.s
        uunpkhi z29.s, z29.h
        add     z31.s, p3/m, z31.s, z29.s
        add     x2, x2, x7
        whilelo p7.b, w2, w3
        whilelo p3.s, w2, w6
        whilelo p4.s, w2, w5
        whilelo p5.s, w2, w4
        whilelo p6.s, w2, w3
        b.any   .L2
        ptrue   p7.b, all
        uaddv   d31, p7, z31.s

but now generates with +dotprod

.L3:
        ld1b    z30.b, p7/z, [x5, x2]
        ld1b    z29.b, p7/z, [x1, x2]
        sub     z30.b, z30.b, z29.b
        udot    z31.s, z30.b, z28.b
        mov     x3, x2
        add     x2, x2, x6
        cmp     w2, w0
        bls     .L3
        incb    x3
        uaddv   d31, p7, z31.s

gcc/ChangeLog:

	PR middle-end/122069
	* config/aarch64/aarch64-sve.md (widen_<sur>sum<mode><vsi2qi>3): New.

gcc/testsuite/ChangeLog:

	PR middle-end/122069
	* gcc.target/aarch64/sve/pr122069_1.c: New test.
	* gcc.target/aarch64/sve/pr122069_2.c: New test.
This commit is contained in:
Tamar Christina 2025-10-18 08:21:56 +01:00
parent bb80fb6e9b
commit 2f719014bf
3 changed files with 142 additions and 0 deletions
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16
gcc/config/aarch64/aarch64-sve.md
View File

@ -7722,6 +7722,22 @@
[(set_attr "sve_type" "sve_int_dot")]
)
;; Define double widen_[su]sum as dotproduct
;; Use dot product to perform double widening sum reductions by
;; changing += a into += (a * 1). i.e. we seed the multiplication with 1.
(define_expand "widen_<sur>sum<mode><vsi2qi>3"
[(set (match_operand:SVE_FULL_SDI 0 "register_operand")
(plus:SVE_FULL_SDI
(unspec:SVE_FULL_SDI
[(match_operand:<VSI2QI> 1 "register_operand")
(match_dup 3)]
DOTPROD)
(match_operand:SVE_FULL_SDI 2 "register_operand")))]
"TARGET_SVE"
{
operands[3] = force_reg (<VSI2QI>mode, CONST1_RTX (<VSI2QI>mode));
})
;; -------------------------------------------------------------------------
;; ---- [INT] Sum of absolute differences
;; -------------------------------------------------------------------------

45
gcc/testsuite/gcc.target/aarch64/sve/pr122069_1.c Normal file
View File

@ -0,0 +1,45 @@
/* { dg-do compile } */
/* { dg-options "-O3 -march=armv8-a+sve -mautovec-preference=sve-only --param vect-epilogues-nomask=0 -fno-schedule-insns -fno-reorder-blocks -fno-schedule-insns2 -fdump-tree-vect-details" }*/
/* { dg-final { check-function-bodies "**" "" } } */
inline char char_abs(char i) {
return (i < 0 ? -i : i);
}
/*
** foo_int:
** ...
** sub z[0-9]+.b, z[0-9]+.b, z[0-9]+.b
** udot z[0-9]+.s, z[0-9]+.b, z[0-9]+.b
** ...
*/
int foo_int(unsigned char *x, unsigned char * restrict y) {
int sum = 0;
for (int i = 0; i < 8000; i++)
sum += char_abs(x[i] - y[i]);
return sum;
}
/*
** foo2_int:
** ...
** add z[0-9]+.h, z[0-9]+.h, z[0-9]+.h
** punpklo p[0-9]+.h, p[0-9]+.b
** uunpklo z[0-9]+.s, z[0-9]+.h
** add z[0-9]+.s, p[0-9]+/m, z[0-9]+.s, z[0-9]+.s
** punpkhi p[0-9]+.h, p[0-9]+.b
** uunpkhi z[0-9]+.s, z[0-9]+.h
** add z[0-9]+.s, p[0-9]+/m, z[0-9]+.s, z[0-9]+.s
** ...
*/
int foo2_int(unsigned short *x, unsigned short * restrict y) {
int sum = 0;
for (int i = 0; i < 8000; i++)
{
x[i] = x[i] + y[i];
sum += x[i];
}
return sum;
}
/* { dg-final { scan-tree-dump-times "LOOP VECTORIZED" 2 "vect" } } */

81
gcc/testsuite/gcc.target/aarch64/sve/pr122069_2.c Normal file
View File

@ -0,0 +1,81 @@
/* { dg-do run } */
/* { dg-require-effective-target aarch64_sve_hw } */
/* { dg-options "-O3 -march=armv8-a+sve -mautovec-preference=sve-only -fdump-tree-vect-details" }*/
inline char char_abs(char i) {
return (i < 0 ? -i : i);
}
__attribute__((noipa))
int foo_int(unsigned char *x, unsigned char * restrict y) {
int sum = 0;
for (int i = 0; i < 100; i++)
sum += char_abs(x[i] - y[i]);
return sum;
}
__attribute__((noipa))
int foo2_int(unsigned short *x, unsigned short * restrict y,
unsigned short * restrict z) {
int sum = 0;
for (int i = 0; i < 100; i++)
{
z[i] = x[i] + y[i];
sum += z[i];
}
return sum;
}
__attribute__((noipa))
int foo_int2(unsigned char *x, unsigned char * restrict y) {
int sum = 0;
#pragma GCC novector
for (int i = 0; i < 100; i++)
sum += char_abs(x[i] - y[i]);
return sum;
}
__attribute__((noipa))
int foo2_int2(unsigned short *x, unsigned short * restrict y,
unsigned short * restrict z) {
int sum = 0;
#pragma GCC novector
for (int i = 0; i < 100; i++)
{
z[i] = x[i] + y[i];
sum += z[i];
}
return sum;
}
int main ()
{
unsigned short a[100];
unsigned short b[100];
unsigned short r1[100];
unsigned short r2[100];
unsigned char c[100];
unsigned char d[100];
#pragma GCC novector
for (int i = 0; i < 100; i++)
{
a[i] = c[i] = i;
b[i] = d[i] = 100 - i;
}
if (foo_int (c, d) != foo_int2 (c, d))
__builtin_abort();
if (foo2_int (a, b, r1) != foo2_int2 (a, b, r2))
__builtin_abort();
#pragma GCC novector
for (int i = 0; i < 100; i++)
if (r1[i] != r2[i])
__builtin_abort ();
return 0;
}
/* { dg-final { scan-tree-dump-times "LOOP VECTORIZED" 2 "vect" } } */