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[AArch64] Unroll ScaleRowDown4Box_NEON

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We can use wider load/store instructions and avoid the need to waste
half of the ADDP/RSHRN vector data. The duplicated UADDLP and UADALP
instructions also provide a good improvement on little cores due to
their limited out-of-order capability.

The mask in the "any" kernel definition is already set up to handle an
unrolling of eight so no change to scale_any.cc is needed.

Reduction in runtimes observed compared to the existing Neon
implementation:

 Cortex-A55: -19.5%
Cortex-A520: -38.3%
 Cortex-A76: -36.0%
Cortex-A715: -18.1%
Cortex-A720: -17.9%
  Cortex-X1: -25.4%
  Cortex-X2: -18.5%
  Cortex-X3:  -8.2%
  Cortex-X4:  -3.8%

Bug: b/42280945
Change-Id: Iebba5da4db5e25af4b9fa5651c7396364dedffba
Reviewed-on: https://chromium-review.googlesource.com/c/libyuv/libyuv/+/5725172
Reviewed-by: Frank Barchard <fbarchard@chromium.org>
This commit is contained in:
George Steed 2024-05-15 21:47:21 +01:00 committed by Frank Barchard
parent dc392094fc
commit 8f039f639c
1 changed files with 13 additions and 9 deletions
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20
source/scale_neon64.cc
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@ -124,22 +124,26 @@ void ScaleRowDown4Box_NEON(const uint8_t* src_ptr,
const uint8_t* src_ptr3 = src_ptr + src_stride * 3;
asm volatile(
"1: \n"
"ld1 {v0.16b}, [%0], #16 \n" // load up 16x4
"ld1 {v1.16b}, [%2], #16 \n"
"ld1 {v2.16b}, [%3], #16 \n"
"ld1 {v3.16b}, [%4], #16 \n"
"subs %w5, %w5, #4 \n"
"ldp q0, q4, [%0], #32 \n" // load up 16x8
"ldp q1, q5, [%2], #32 \n"
"ldp q2, q6, [%3], #32 \n"
"ldp q3, q7, [%4], #32 \n"
"subs %w5, %w5, #8 \n"
"uaddlp v0.8h, v0.16b \n"
"uaddlp v4.8h, v4.16b \n"
"prfm pldl1keep, [%0, 448] \n" // prefetch 7 lines ahead
"uadalp v0.8h, v1.16b \n"
"uadalp v4.8h, v5.16b \n"
"prfm pldl1keep, [%2, 448] \n"
"uadalp v0.8h, v2.16b \n"
"uadalp v4.8h, v6.16b \n"
"prfm pldl1keep, [%3, 448] \n"
"uadalp v0.8h, v3.16b \n"
"uadalp v4.8h, v7.16b \n"
"prfm pldl1keep, [%4, 448] \n"
"addp v0.8h, v0.8h, v0.8h \n"
"addp v0.8h, v0.8h, v4.8h \n"
"rshrn v0.8b, v0.8h, #4 \n" // divide by 16 w/rounding
"st1 {v0.s}[0], [%1], #4 \n"
"str d0, [%1], #8 \n"
"b.gt 1b \n"
: "+r"(src_ptr), // %0
"+r"(dst_ptr), // %1
@ -148,7 +152,7 @@ void ScaleRowDown4Box_NEON(const uint8_t* src_ptr,
"+r"(src_ptr3), // %4
"+r"(dst_width) // %5
:
: "memory", "cc", "v0", "v1", "v2", "v3");
: "memory", "cc", "v0", "v1", "v2", "v3", "v4", "v5", "v6", "v7");
}
// Down scale from 4 to 3 pixels. Use the neon multilane read/write