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vc4: Use NEON to speed up utile loads on Pi2.

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We had a lot of memcpy call overhead because gpu_stride wasn't being
inlined.  But if you split out the stride==8 and stride==16 cases like
this code does while still using memcpy, you'd no longer have glibc's
NEON memcpy applied at which point we'd be doing 16 uncached reads
instead of 64/(NEON memcpy granularity), for about a 30% performance
hit.  By hand writing the assembly, we can get a whole cacheline
loaded at a time.

Unfortunately, NEON intrinsics turned out to be unusable -- they
didn't have the vldm instruction available.

Note that, for now, the NEON code is only enabled when building for ARMv7
(Pi 2+).  We may want to do runtime detection for the Raspbian case, in
the future.

Improves 1024x1024 GetTexImage by 208.256% +/- 7.07029% (n=10).
This commit is contained in:
Eric Anholt
2017-01-05 15:11:30 -08:00
parent 347b69e7d7
commit 4d30024238
3 changed files with 115 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
src/gallium/drivers/vc4/Makefile.am
View File

@@ -40,3 +40,9 @@ noinst_LTLIBRARIES = libvc4.la
libvc4_la_SOURCES = $(C_SOURCES)
libvc4_la_LIBADD = $(SIM_LIB) $(VC4_LIBS)
libvc4_la_LDFLAGS = $(SIM_LDFLAGS)
noinst_LTLIBRARIES += libvc4_neon.la
libvc4_la_LIBADD += libvc4_neon.la
libvc4_neon_la_SOURCES = vc4_tiling_lt.c
libvc4_neon_la_CFLAGS = $(AM_CFLAGS) -DVC4_BUILD_NEON

48
src/gallium/drivers/vc4/vc4_tiling.h
View File

@@ -62,12 +62,18 @@ vc4_utile_height(int cpp)
}
bool vc4_size_is_lt(uint32_t width, uint32_t height, int cpp) ATTRIBUTE_CONST;
void vc4_load_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_store_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_load_lt_image_base(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_store_lt_image_base(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_load_lt_image_neon(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_store_lt_image_neon(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box);
void vc4_load_tiled_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
uint8_t tiling_format, int cpp,
@@ -77,4 +83,34 @@ void vc4_store_tiled_image(void *dst, uint32_t dst_stride,
uint8_t tiling_format, int cpp,
const struct pipe_box *box);
/* If we're building for ARMv7 (Pi 2+), assume it has NEON. For Raspbian we
* should extend this to have some runtime detection of being built for ARMv6
* on a Pi 2+.
*/
#if defined(__ARM_ARCH) && __ARM_ARCH >= 7
#define NEON_SUFFIX(x) x ## _neon
#else
#define NEON_SUFFIX(x) x ## _base
#endif
static inline void
vc4_load_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
{
NEON_SUFFIX(vc4_load_lt_image)(dst, dst_stride, src, src_stride,
cpp, box);
}
static inline void
vc4_store_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
{
NEON_SUFFIX(vc4_store_lt_image)(dst, dst_stride, src, src_stride,
cpp, box);
}
#undef NEON_SUFFIX
#endif /* VC4_TILING_H */

79
src/gallium/drivers/vc4/vc4_tiling_lt.c
View File

@@ -25,12 +25,22 @@
*
* Helper functions from vc4_tiling.c that will be compiled for using NEON
* assembly or not.
*
* If VC4_BUILD_NEON is set, then the functions will be suffixed with _neon.
* They will only use NEON assembly if __ARM_ARCH is also set, to keep the x86
* sim build working.
*/
#include <string.h>
#include "pipe/p_state.h"
#include "vc4_tiling.h"
#ifdef VC4_BUILD_NEON
#define NEON_TAG(x) x ## _neon
#else
#define NEON_TAG(x) x ## _base
#endif
/** Returns the stride in bytes of a 64-byte microtile. */
static uint32_t
vc4_utile_stride(int cpp)
@@ -48,14 +58,59 @@ vc4_utile_stride(int cpp)
}
static void
vc4_load_utile(void *dst, void *src, uint32_t dst_stride, uint32_t cpp)
vc4_load_utile(void *cpu, void *gpu, uint32_t cpu_stride, uint32_t cpp)
{
uint32_t src_stride = vc4_utile_stride(cpp);
for (uint32_t src_offset = 0; src_offset < 64; src_offset += src_stride) {
memcpy(dst, src + src_offset, src_stride);
dst += dst_stride;
uint32_t gpu_stride = vc4_utile_stride(cpp);
#if defined(VC4_BUILD_NEON) && defined(__ARM_ARCH)
if (gpu_stride == 8) {
__asm__ volatile (
/* Load from the GPU in one shot, no interleave, to
* d0-d7.
*/
"vldm %0, {q0, q1, q2, q3};\n"
/* Store each 8-byte line to cpu-side destination,
* incrementing it by the stride each time.
*/
"vst1.8 d0, [%1], %r2;\n"
"vst1.8 d1, [%1], %r2;\n"
"vst1.8 d2, [%1], %r2;\n"
"vst1.8 d3, [%1], %r2;\n"
"vst1.8 d4, [%1], %r2;\n"
"vst1.8 d5, [%1], %r2;\n"
"vst1.8 d6, [%1], %r2;\n"
"vst1.8 d7, [%1];\n"
:
: "r"(gpu), "r"(cpu), "r"(cpu_stride)
: "q0", "q1", "q2", "q3");
} else {
assert(gpu_stride == 16);
__asm__ volatile (
/* Load from the GPU in one shot, no interleave, to
* d0-d7.
*/
"vldm %0, {q0, q1, q2, q3};\n"
/* Store each 16-byte line in 2 parts to the cpu-side
* destination. (vld1 can only store one d-register
* at a time).
*/
"vst1.8 d0, [%1], %r3;\n"
"vst1.8 d1, [%2], %r3;\n"
"vst1.8 d2, [%1], %r3;\n"
"vst1.8 d3, [%2], %r3;\n"
"vst1.8 d4, [%1], %r3;\n"
"vst1.8 d5, [%2], %r3;\n"
"vst1.8 d6, [%1];\n"
"vst1.8 d7, [%2];\n"
:
: "r"(gpu), "r"(cpu), "r"(cpu + 8), "r"(cpu_stride)
: "q0", "q1", "q2", "q3");
}
#else
for (uint32_t gpu_offset = 0; gpu_offset < 64; gpu_offset += gpu_stride) {
memcpy(cpu, gpu + gpu_offset, gpu_stride);
cpu += cpu_stride;
}
#endif
}
static void
@@ -70,9 +125,9 @@ vc4_store_utile(void *dst, void *src, uint32_t src_stride, uint32_t cpp)
}
void
vc4_load_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
NEON_TAG(vc4_load_lt_image)(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
{
uint32_t utile_w = vc4_utile_width(cpp);
uint32_t utile_h = vc4_utile_height(cpp);
@@ -91,9 +146,9 @@ vc4_load_lt_image(void *dst, uint32_t dst_stride,
}
void
vc4_store_lt_image(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
NEON_TAG(vc4_store_lt_image)(void *dst, uint32_t dst_stride,
void *src, uint32_t src_stride,
int cpp, const struct pipe_box *box)
{
uint32_t utile_w = vc4_utile_width(cpp);
uint32_t utile_h = vc4_utile_height(cpp);