1/*
2 * Copyright 2017 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkJumper_misc_DEFINED
9#define SkJumper_misc_DEFINED
10
11#include <string.h>  // for memcpy()
12
13// Miscellany used by SkJumper_stages.cpp and SkJumper_stages_lowp.cpp.
14
15// Every function in this file should be marked static and inline using SI.
16#if defined(__clang__)
17    #define SI __attribute__((always_inline)) static inline
18#else
19    #define SI static inline
20#endif
21
22
23template <typename T, typename P>
24SI T unaligned_load(const P* p) {  // const void* would work too, but const P* helps ARMv7 codegen.
25    T v;
26    memcpy(&v, p, sizeof(v));
27    return v;
28}
29
30template <typename T, typename P>
31SI void unaligned_store(P* p, T v) {
32    memcpy(p, &v, sizeof(v));
33}
34
35template <typename Dst, typename Src>
36SI Dst bit_cast(const Src& src) {
37    static_assert(sizeof(Dst) == sizeof(Src), "");
38    return unaligned_load<Dst>(&src);
39}
40
41template <typename Dst, typename Src>
42SI Dst widen_cast(const Src& src) {
43    static_assert(sizeof(Dst) > sizeof(Src), "");
44    Dst dst;
45    memcpy(&dst, &src, sizeof(Src));
46    return dst;
47}
48
49// Our program is an array of void*, either
50//   - 1 void* per stage with no context pointer, the next stage;
51//   - 2 void* per stage with a context pointer, first the context pointer, then the next stage.
52
53// load_and_inc() steps the program forward by 1 void*, returning that pointer.
54SI void* load_and_inc(void**& program) {
55#if defined(__GNUC__) && defined(__x86_64__)
56    // If program is in %rsi (we try to make this likely) then this is a single instruction.
57    void* rax;
58    asm("lodsq" : "=a"(rax), "+S"(program));  // Write-only %rax, read-write %rsi.
59    return rax;
60#else
61    // On ARM *program++ compiles into pretty ideal code without any handholding.
62    return *program++;
63#endif
64}
65
66// Lazily resolved on first cast.  Does nothing if cast to Ctx::None.
67struct Ctx {
68    struct None {};
69
70    void*   ptr;
71    void**& program;
72
73    explicit Ctx(void**& p) : ptr(nullptr), program(p) {}
74
75    template <typename T>
76    operator T*() {
77        if (!ptr) { ptr = load_and_inc(program); }
78        return (T*)ptr;
79    }
80    operator None() { return None{}; }
81};
82
83#endif//SkJumper_misc_DEFINED
84