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AArch64: add double widen_sum optab using dotprod for Adv.SIMD [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:
        ldr     q0, [x0, x2]
        ldr     q28, [x1, x2]
        sub     v28.16b, v0.16b, v28.16b
        zip1    v29.16b, v28.16b, v31.16b
        zip2    v28.16b, v28.16b, v31.16b
        uaddw   v30.4s, v30.4s, v29.4h
        uaddw2  v30.4s, v30.4s, v29.8h
        uaddw   v30.4s, v30.4s, v28.4h
        uaddw2  v30.4s, v30.4s, v28.8h
        add     x2, x2, 16
        cmp     x2, x3
        bne     .L2
        addv    s31, v30.4s

but now generates with +dotprod

.L2:
        ldr     q29, [x0, x2]
        ldr     q28, [x1, x2]
        sub     v28.16b, v29.16b, v28.16b
        udot    v31.4s, v28.16b, v30.16b
        add     x2, x2, 16
        cmp     x2, x3
        bne     .L2
        addv    s31, v31.4s

gcc/ChangeLog:

	PR middle-end/122069
	* config/aarch64/aarch64-simd.md (widen_ssum<mode><vsi2qi>3): New.
	(widen_usum<mode><vsi2qi>3): New.

gcc/testsuite/ChangeLog:

	PR middle-end/122069
	* gcc.target/aarch64/pr122069_3.c: New test.
	* gcc.target/aarch64/pr122069_4.c: New test.
This commit is contained in:
Tamar Christina 2025-10-18 08:20:07 +01:00
parent b394181afd
commit c8dc5d5070
3 changed files with 154 additions and 0 deletions
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32
gcc/config/aarch64/aarch64-simd.md
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@ -4703,6 +4703,38 @@
DONE;
})
(define_expand "widen_ssum<mode><vsi2qi>3"
[(set (match_operand:VS 0 "register_operand")
(plus:VS (sign_extend:VS
(match_operand:<VSI2QI> 1 "register_operand"))
(match_operand:VS 2 "register_operand")))]
"TARGET_DOTPROD"
{
rtx ones = force_reg (<VSI2QI>mode, CONST1_RTX (<VSI2QI>mode));
emit_insn (gen_sdot_prod<mode><vsi2qi> (operands[0], operands[1], ones,
operands[2]));
DONE;
}
)
;; 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_usum<mode><vsi2qi>3"
[(set (match_operand:VS 0 "register_operand")
(plus:VS (zero_extend:VS
(match_operand:<VSI2QI> 1 "register_operand"))
(match_operand:VS 2 "register_operand")))]
"TARGET_DOTPROD"
{
rtx ones = force_reg (<VSI2QI>mode, CONST1_RTX (<VSI2QI>mode));
emit_insn (gen_udot_prod<mode><vsi2qi> (operands[0], operands[1], ones,
operands[2]));
DONE;
}
)
;; Use dot product to perform double widening sum reductions by
;; changing += a into += (a * 1). i.e. we seed the multiplication with 1.
(define_insn "aarch64_<ANY_EXTEND:su>subw<mode>"
[(set (match_operand:<VWIDE> 0 "register_operand" "=w")
(minus:<VWIDE> (match_operand:<VWIDE> 1 "register_operand" "w")

41
gcc/testsuite/gcc.target/aarch64/pr122069_3.c Normal file
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@ -0,0 +1,41 @@
/* { dg-do compile } */
/* { dg-options "-O3 -march=armv8.2-a+dotprod -mautovec-preference=asimd-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 v[0-9]+.16b, v[0-9]+.16b, v[0-9]+.16b
** udot v[0-9]+.4s, v[0-9]+.16b, v[0-9]+.16b
** ...
*/
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 v[0-9]+.8h, v[0-9]+.8h, v[0-9]+.8h
** uaddw v[0-9]+.4s, v[0-9]+.4s, v[0-9]+.4h
** uaddw2 v[0-9]+.4s, v[0-9]+.4s, v[0-9]+.8h
** ...
*/
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/pr122069_4.c Normal file
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@ -0,0 +1,81 @@
/* { dg-do run } */
/* { dg-require-effective-target arm_v8_2a_dotprod_neon_hw }*/
/* { dg-options "-O3 -march=armv8.2-a+dotprod -mautovec-preference=asimd-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" } } */