[x265] [PATCH 2/3] AArch64: Refactor loop unroll pragmas in dct primitives

[Hari Limaye]

HI Chen,

Thank you for reviewing these patches.


>In my view, compiler option is not good idea, unroll these loop in manual are more better, it helpful us find out optimzie point and improve algorithm future.
>
>For example, split DCT into deep Even part (EE/EEE, etc) does not get good performance

This series is intended to be largely NFC and to simply silence compiler warnings for the AArch64 intrinsics files. We plan to push optimisation patches for DCT primitives after this series.

Many thanks,
Hari
From: x265-devel <x265-devel-bounces at videolan.org> on behalf of Hari Limaye <hari.limaye at arm.com>
Date: Tuesday, 20 August 2024 at 18:42
To: x265-devel at videolan.org <x265-devel at videolan.org>
Subject: [x265] [PATCH 2/3] AArch64: Refactor loop unroll pragmas in dct primitives
Make #pragma unroll directives portable for Clang and GCC, as currently
GCC will simply ignore the unsupported directives.
---
 source/common/aarch64/dct-prim.cpp | 36 ++++++++++++++++++------------
 1 file changed, 22 insertions(+), 14 deletions(-)

diff --git a/source/common/aarch64/dct-prim.cpp b/source/common/aarch64/dct-prim.cpp
index 416532e54..acc50d4f4 100644
--- a/source/common/aarch64/dct-prim.cpp
+++ b/source/common/aarch64/dct-prim.cpp
@@ -5,6 +5,14 @@

 #include <arm_neon.h>

+#define X265_PRAGMA(text)       _Pragma(#text)
+#if defined(__clang__)
+#define X265_PRAGMA_UNROLL(n)   X265_PRAGMA(unroll(n))
+#elif defined(__GNUC__)
+#define X265_PRAGMA_UNROLL(n)   X265_PRAGMA(GCC unroll (n))
+#else
+#define X265_PRAGMA_UNROLL(n)
+#endif

 namespace
 {
@@ -472,12 +480,12 @@ static void partialButterflyInverse16_neon(const int16_t *src, int16_t *orig_dst
     const int add = 1 << (shift - 1);


-#pragma unroll(4)
+X265_PRAGMA_UNROLL(4)
     for (j = 0; j < line; j += 4)
     {
         /* Utilizing symmetry properties to the maximum to minimize the number of multiplications */

-#pragma unroll(2)
+X265_PRAGMA_UNROLL(2)
         for (k = 0; k < 2; k++)
         {
             int32x4_t s;
@@ -496,7 +504,7 @@ static void partialButterflyInverse16_neon(const int16_t *src, int16_t *orig_dst
         EE[3] = vsubq_s32(EEE[0] , EEO[0]);


-#pragma unroll(1)
+X265_PRAGMA_UNROLL(1)
         for (k = 0; k < 4; k += 4)
         {
             int32x4_t s[4];
@@ -522,14 +530,14 @@ static void partialButterflyInverse16_neon(const int16_t *src, int16_t *orig_dst
         static const int32x4_t max = vdupq_n_s32(32767);
         const int32x4_t minus_shift = vdupq_n_s32(-shift);

-#pragma unroll(4)
+X265_PRAGMA_UNROLL(4)
         for (k = 0; k < 4; k++)
         {
             E[k] = vaddq_s32(EE[k] , EO[k]);
             E[k + 4] = vsubq_s32(EE[3 - k] , EO[3 - k]);
         }

-#pragma unroll(2)
+X265_PRAGMA_UNROLL(2)
         for (k = 0; k < 8; k += 4)
         {
             int32x4_t s[4];
@@ -584,7 +592,7 @@ static void partialButterflyInverse16_neon(const int16_t *src, int16_t *orig_dst
         }


-#pragma unroll(2)
+X265_PRAGMA_UNROLL(2)
         for (k = 0; k < 8; k += 4)
         {
             int32x4_t t;
@@ -657,10 +665,10 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst
     int16x4_t dst[32];
     int add = 1 << (shift - 1);

-#pragma unroll (8)
+X265_PRAGMA_UNROLL(8)
     for (j = 0; j < line; j += 4)
     {
-#pragma unroll (4)
+X265_PRAGMA_UNROLL(4)
         for (k = 0; k < 16; k += 4)
         {
             int32x4_t s[4];
@@ -681,7 +689,7 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst
         }


-#pragma unroll (2)
+X265_PRAGMA_UNROLL(2)
         for (k = 0; k < 8; k += 4)
         {
             int32x4_t s[4];
@@ -721,7 +729,7 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst
             EEO[k + 3] = s[3];
         }

-#pragma unroll (2)
+X265_PRAGMA_UNROLL(2)
         for (k = 0; k < 2; k++)
         {
             int32x4_t s;
@@ -736,14 +744,14 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst
         EEE[1] = vaddq_s32(EEEE[1], EEEO[1]);
         EEE[2] = vsubq_s32(EEEE[1], EEEO[1]);

-#pragma unroll (4)
+X265_PRAGMA_UNROLL(4)
         for (k = 0; k < 4; k++)
         {
             EE[k] = vaddq_s32(EEE[k], EEO[k]);
             EE[k + 4] = vsubq_s32((EEE[3 - k]), (EEO[3 - k]));
         }

-#pragma unroll (8)
+X265_PRAGMA_UNROLL(8)
         for (k = 0; k < 8; k++)
         {
             E[k] = vaddq_s32(EE[k], EO[k]);
@@ -755,7 +763,7 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst



-#pragma unroll (16)
+X265_PRAGMA_UNROLL(16)
         for (k = 0; k < 16; k++)
         {
             int32x4_t adde = vaddq_s32(vdupq_n_s32(add), E[k]);
@@ -777,7 +785,7 @@ static void partialButterflyInverse32_neon(const int16_t *src, int16_t *orig_dst
         }


-#pragma unroll (8)
+X265_PRAGMA_UNROLL(8)
         for (k = 0; k < 32; k += 4)
         {
             int16x4_t x0 = dst[k + 0];
--
2.42.1
IMPORTANT NOTICE: The contents of this email and any attachments are confidential and may also be privileged. If you are not the intended recipient, please notify the sender immediately and do not disclose the contents to any other person, use it for any purpose, or store or copy the information in any medium. Thank you.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.videolan.org/pipermail/x265-devel/attachments/20240821/c6894306/attachment-0001.htm>