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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.
*/
#ifndef SkJumper_misc_DEFINED
#define SkJumper_misc_DEFINED
#include "SkJumper.h" // for memcpy()
// Miscellany used by SkJumper_stages.cpp and SkJumper_vectors.h.
// Every function in this file should be marked static and inline using SI.
#if defined(JUMPER)
#define SI __attribute__((always_inline)) static inline
#else
#define SI static inline
#endif
template <typename T, typename P>
SI T unaligned_load(const P* p) { // const void* would work too, but const P* helps ARMv7 codegen.
T v;
memcpy(&v, p, sizeof(v));
return v;
}
template <typename T, typename P>
SI void unaligned_store(P* p, T v) {
memcpy(p, &v, sizeof(v));
}
template <typename Dst, typename Src>
SI Dst bit_cast(const Src& src) {
static_assert(sizeof(Dst) == sizeof(Src), "");
return unaligned_load<Dst>(&src);
}
template <typename Dst, typename Src>
SI Dst widen_cast(const Src& src) {
static_assert(sizeof(Dst) > sizeof(Src), "");
Dst dst;
memcpy(&dst, &src, sizeof(Src));
return dst;
}
// Our program is an array of void*, either
// - 1 void* per stage with no context pointer, the next stage;
// - 2 void* per stage with a context pointer, first the context pointer, then the next stage.
// load_and_inc() steps the program forward by 1 void*, returning that pointer.
SI void* load_and_inc(void**& program) {
#if defined(__GNUC__) && defined(__x86_64__)
// If program is in %rsi (we try to make this likely) then this is a single instruction.
void* rax;
asm("lodsq" : "=a"(rax), "+S"(program)); // Write-only %rax, read-write %rsi.
return rax;
#else
// On ARM *program++ compiles into pretty ideal code without any handholding.
return *program++;
#endif
}
// LazyCtx doesn't do anything unless you call operator T*(), encapsulating the logic
// from above that stages without a context pointer are represented by just 1 void*.
struct LazyCtx {
void* ptr;
void**& program;
explicit LazyCtx(void**& p) : ptr(nullptr), program(p) {}
template <typename T>
operator T*() {
if (!ptr) { ptr = load_and_inc(program); }
return (T*)ptr;
}
};
#endif//SkJumper_misc_DEFINED
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