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/*
* Copyright 2017 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkCpu.h"
#include "SkOpts.h"
#include "SkRasterPipeline.h"
#include "SkStream.h"
#include <sys/mman.h>
#include "SkSplicer_generated.h"
#include "SkSplicer_shared.h"
// Uncomment to dump output with IACA markers.
// #define IACA_DUMP "/tmp/dump.o"
// https://software.intel.com/en-us/articles/intel-architecture-code-analyzer
// $ ./iaca.sh -arch HSW -64 -mark 0 /tmp/dump.o | less
namespace {
// Stages expect these constants to be set to these values.
// It's fine to rearrange and add new ones if you update SkSplicer_constants.
static const SkSplicer_constants kConstants = {
0x000000ff, 1.0f, 255.0f, 1/255.0f,
0.0025f, 0.6975f, 0.3000f, 1/12.92f, 0.055f, // from_srgb
12.46f, 0.411192f, 0.689206f, -0.0988f, 0.0043f, // to_srgb
};
// Short x86-64 instruction sequences that we'll use as glue to splice together Stages.
static const uint8_t vzeroupper[] = { 0xc5, 0xf8, 0x77 }; // clear top half of all ymm
static const uint8_t ret[] = { 0xc3 }; // return
static const uint8_t movabsq_rcx[] = { 0x48, 0xb9 }; // move next 8 bytes into rcx
static const uint8_t movabsq_rdx[] = { 0x48, 0xba }; // move next 8 bytes into rdx
static const uint8_t addq_8_rdi[] = { 0x48, 0x83, 0xc7, 0x08 }; // rdi += 8
static const uint8_t cmpq_rsi_rdi[] = { 0x48, 0x39, 0xf7 }; // rdi cmp? rsi
static const uint8_t jb_near[] = { 0x0f, 0x8c }; // jump relative next 4 bytes
// if cmp set unsigned < bit
// We do this a lot, so it's nice to infer the correct size. Works fine with arrays.
template <typename T>
void splice(SkWStream* stream, const T& val) {
stream->write(&val, sizeof(val));
}
#ifdef IACA_DUMP
static const uint8_t ud2[] = { 0x0f, 0x0b }; // undefined... crashes when run
static const uint8_t nop3[] = { 0x64, 0x67, 0x90 }; // 3 byte no-op
static const uint8_t movl_ebx[] = { 0xbb }; // move next 4 bytes into ebx
static void iaca_start(SkWStream* stream) {
splice(stream, ud2);
splice(stream, movl_ebx);
splice(stream, 111);
splice(stream, nop3);
}
static void iaca_end(SkWStream* stream) {
splice(stream, movl_ebx);
splice(stream, 222);
splice(stream, nop3);
splice(stream, ud2);
}
#else
static void iaca_start(SkWStream*) {}
static void iaca_end (SkWStream*) {}
#endif
// Copy len bytes from src to memory that's executable. cleanup with cleanup_executable_mem().
static void* copy_to_executable_mem(const void* src, size_t len) {
if (src && len) {
// TODO: w^x
auto fn = mmap(nullptr, len, PROT_WRITE|PROT_EXEC, MAP_ANON|MAP_PRIVATE, -1, 0);
return memcpy(fn, src, len);
}
return nullptr;
}
static void cleanup_executable_mem(void* fn, size_t len) {
if (fn) {
munmap(fn, len);
}
}
struct Spliced {
Spliced(const SkRasterPipeline::Stage* stages, int nstages) {
// We always create a backup interpreter pipeline,
// - to handle any program we can't, and
// - to handle the n < 8 tails.
fBackup = SkOpts::compile_pipeline(stages, nstages);
fSplicedLen = 0;
fSpliced = nullptr;
// If we return early anywhere in here, !fSpliced means we'll use fBackup instead.
// To keep things simple, only one target supported: Haswell+ x86-64.
if (!SkCpu::Supports(SkCpu::HSW) || sizeof(void*) != 8) {
return;
}
SkDynamicMemoryWStream buf;
// Put the address of kConstants in rcx, Stage argument 4 "k".
splice(&buf, movabsq_rcx);
splice(&buf, &kConstants);
// We'll loop back to here as long as x<n after x+=8.
iaca_start(&buf);
auto loop_start = buf.bytesWritten(); // Think of this like a label, loop_start:
for (int i = 0; i < nstages; i++) {
// If a stage has a context pointer, load it into rdx, Stage argument 3 "ctx".
if (stages[i].ctx) {
splice(&buf, movabsq_rdx);
splice(&buf, stages[i].ctx);
}
// Splice in the code for the Stages, generated offline into SkSplicer_generated.h.
switch(stages[i].stage) {
case SkRasterPipeline::clear: splice(&buf, kSplice_clear ); break;
case SkRasterPipeline::plus_: splice(&buf, kSplice_plus ); break;
case SkRasterPipeline::srcover: splice(&buf, kSplice_srcover ); break;
case SkRasterPipeline::dstover: splice(&buf, kSplice_dstover ); break;
case SkRasterPipeline::clamp_0: splice(&buf, kSplice_clamp_0 ); break;
case SkRasterPipeline::clamp_1: splice(&buf, kSplice_clamp_1 ); break;
case SkRasterPipeline::clamp_a: splice(&buf, kSplice_clamp_a ); break;
case SkRasterPipeline::swap: splice(&buf, kSplice_swap ); break;
case SkRasterPipeline::move_src_dst: splice(&buf, kSplice_move_src_dst); break;
case SkRasterPipeline::move_dst_src: splice(&buf, kSplice_move_dst_src); break;
case SkRasterPipeline::premul: splice(&buf, kSplice_premul ); break;
case SkRasterPipeline::unpremul: splice(&buf, kSplice_unpremul ); break;
case SkRasterPipeline::from_srgb: splice(&buf, kSplice_from_srgb ); break;
case SkRasterPipeline::to_srgb: splice(&buf, kSplice_to_srgb ); break;
case SkRasterPipeline::scale_u8: splice(&buf, kSplice_scale_u8 ); break;
case SkRasterPipeline::load_8888: splice(&buf, kSplice_load_8888 ); break;
case SkRasterPipeline::store_8888: splice(&buf, kSplice_store_8888 ); break;
case SkRasterPipeline::load_f16: splice(&buf, kSplice_load_f16 ); break;
case SkRasterPipeline::store_f16: splice(&buf, kSplice_store_f16 ); break;
// No joy (probably just not yet implemented).
default:
//SkDebugf("SkSplicer can't yet handle stage %d.\n", stages[i].stage);
return;
}
}
// See if we should loop back to handle more pixels.
splice(&buf, addq_8_rdi); // x += 8
splice(&buf, cmpq_rsi_rdi); // if (x < n)
splice(&buf, jb_near); // goto loop_start;
splice(&buf, (int)loop_start - (int)(buf.bytesWritten() + 4));
iaca_end(&buf);
// Nope! We're done.
splice(&buf, vzeroupper);
splice(&buf, ret);
auto data = buf.detachAsData();
fSplicedLen = data->size();
fSpliced = copy_to_executable_mem(data->data(), fSplicedLen);
#ifdef IACA_DUMP
SkFILEWStream(IACA_DUMP).write(data->data(), data->size());
#endif
}
// Spliced is stored in a std::function, so it needs to be copyable.
Spliced(const Spliced& o) : fBackup (o.fBackup)
, fSplicedLen(o.fSplicedLen)
, fSpliced (copy_to_executable_mem(o.fSpliced, fSplicedLen)) {}
~Spliced() {
cleanup_executable_mem(fSpliced, fSplicedLen);
}
// Here's where we call fSpliced if we created it, fBackup if not.
void operator()(size_t x, size_t y, size_t n) const {
// TODO: The looping logic is probably not correct for handling n<8 tails.
if (fSpliced) {
// TODO: At some point we will want to pass in y...
using Fn = void(size_t x, size_t n);
((Fn*)fSpliced)(x,n);
// Fall through to fBackup for any n<8 last pixels.
size_t body = n/8*8;
x += body;
n -= body;
}
fBackup(x,y,n);
}
std::function<void(size_t, size_t, size_t)> fBackup;
size_t fSplicedLen;
void* fSpliced;
};
}
std::function<void(size_t, size_t, size_t)> SkRasterPipeline::jit() const {
return Spliced(fStages.data(), SkToInt(fStages.size()));
}
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