1 /*
2  * Copyright 2016 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 #include "Benchmark.h"
9 #include "SkTypes.h"
10 
11 /**
12  * There's a good variety of ways to pack from int down to uint16_t with SSE,
13  * depending on the specific instructions available.
14  *
15  * SSE2 offers an int -> int16_t pack instruction.  We can use this in two ways:
16  *    - subtract off 32768, int -> int16_t, add 32768 back                                  (sse2_a)
17  *    - first artificially sign extend the (positive) value in our int, then int -> int16_t (sse2_b)
18  * SSSE3 adds a byte shuffle, so we just put the bytes where we want them.                  (ssse3)
19  * SSE41 added an int -> uint16_t pack instruction.                                         (sse41)
20  *
21  * Findings so far:
22  *   - sse41 < ssse3 <<< sse2_b < sse2_a;
23  *   - the ssse3 version is only slightly slower than the sse41 version, maybe not at all
24  *   - the sse2_a is only slightly slower than the sse2_b version
25  *   - the ssse3 and sse41 versions are about 3x faster than either sse2 version
26  *   - the sse41 version seems to cause some code generation trouble.
27  */
28 
29 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
30 
31 #include <immintrin.h>
32 
33 template <__m128i (kernel)(__m128i)>
34 class pack_int_uint16_t_Bench : public Benchmark {
35 public:
pack_int_uint16_t_Bench(const char * impl)36     pack_int_uint16_t_Bench(const char* impl) {
37         fName.append("pack_int_uint16_t_");
38         fName.append(impl);
39     }
40 
isSuitableFor(Backend backend)41     bool isSuitableFor(Backend backend) override { return backend == kNonRendering_Backend; }
onGetName()42     const char* onGetName() override { return fName.c_str(); }
43 
onDraw(int loops,SkCanvas *)44     void onDraw(int loops, SkCanvas*) override {
45         __m128i x = _mm_set1_epi32(0x42424242);
46         while (loops --> 0) {
47             x = kernel(x);
48         }
49 
50         volatile int blackhole = 0;
51         blackhole ^= _mm_cvtsi128_si32(x);
52     }
53 
54     SkString fName;
55 };
56 
57 namespace {
sse2_a(__m128i x)58     __m128i sse2_a(__m128i x) {
59         x = _mm_sub_epi32(x, _mm_set1_epi32(0x8000));
60         return _mm_add_epi16(_mm_packs_epi32(x,x), _mm_set1_epi16((short)0x8000));
61     }
62 }
63 DEF_BENCH( return new pack_int_uint16_t_Bench<sse2_a>("sse2_a"); )
64 
65 namespace {
sse2_b(__m128i x)66     __m128i sse2_b(__m128i x) {
67         x = _mm_srai_epi32(_mm_slli_epi32(x, 16), 16);
68         return _mm_packs_epi32(x,x);
69     }
70 }
71 DEF_BENCH( return new pack_int_uint16_t_Bench<sse2_b>("sse2_b"); )
72 
73 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSSE3
74 namespace {
ssse3(__m128i x)75     __m128i ssse3(__m128i x) {
76         // TODO: Can we force the bench to load the mask inside the loop?  Would be more realistic.
77         const int _ = ~0;
78         return _mm_shuffle_epi8(x, _mm_setr_epi8(0,1, 4,5, 8,9, 12,13, _,_,_,_,_,_,_,_));
79     }
80 }
81 DEF_BENCH( return new pack_int_uint16_t_Bench<ssse3>("ssse3"); )
82 #endif
83 
84 #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE41
85 namespace {
sse41(__m128i x)86     __m128i sse41(__m128i x) {
87         return _mm_packus_epi32(x,x);
88     }
89 }
90 DEF_BENCH( return new pack_int_uint16_t_Bench<sse41>("sse41"); )
91 #endif
92 
93 #endif  // SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
94