float xfermodes (burn, dodge, softlight) in Sk8f, possibly using AVX.

Xfermode_ColorDodge_aa	10.3ms -> 7.85ms	0.76x
 Xfermode_SoftLight_aa	13.8ms -> 10.2ms	0.74x
 Xfermode_ColorBurn_aa	10.7ms -> 7.82ms	0.73x
    Xfermode_SoftLight	33.6ms -> 23.2ms	0.69x
   Xfermode_ColorDodge	  25ms -> 16.5ms	0.66x
    Xfermode_ColorBurn	26.1ms -> 16.6ms	0.63x

Ought to be no pixel diffs:
https://gold.skia.org/search2?issue=1432903002&unt=true&query=source_type%3Dgm&master=false

Incidental stuff:

I made the SkNx(T) constructors implicit to make writing math expressions simpler.
This allows us to write expressions like
  Sk4f v;
  ...
  v = v*4;
rather than
  Sk4f v;
  ...
  v = v * Sk4f(4);

As written it only works when the constant is on the right-hand side,
so expressions like `(Sk4f(1) - da)` have to stay for now.  I plan on
following up with a CL that lets those become `(1 - da)` too.

BUG=skia:4117
CQ_EXTRA_TRYBOTS=client.skia:Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-SKNX_NO_SIMD-Trybot

Review URL: https://codereview.chromium.org/1432903002

1 files changed, 6 insertions, 6 deletions

diff --git a/src/opts/SkNx_sse.h b/src/opts/SkNx_sse.h
index 6e9c59c5cb..32e94a6d66 100644
--- a/src/opts/SkNx_sse.h
+++ b/src/opts/SkNx_sse.h
@@ -19,7 +19,7 @@ public:
     SkNf(const __m128& vec) : fVec(vec) {}
 
     SkNf() {}
-    explicit SkNf(float val) : fVec(_mm_set1_ps(val)) {}
+    SkNf(float val) : fVec(_mm_set1_ps(val)) {}
     static SkNf Load(const float vals[2]) {
         return _mm_castsi128_ps(_mm_loadl_epi64((const __m128i*)vals));
     }
@@ -68,7 +68,7 @@ public:
     SkNi(const __m128i& vec) : fVec(vec) {}
 
     SkNi() {}
-    explicit SkNi(int val) : fVec(_mm_set1_epi32(val)) {}
+    SkNi(int val) : fVec(_mm_set1_epi32(val)) {}
     static SkNi Load(const int vals[4]) { return _mm_loadu_si128((const __m128i*)vals); }
     SkNi(int a, int b, int c, int d) : fVec(_mm_setr_epi32(a,b,c,d)) {}
 
@@ -106,7 +106,7 @@ public:
     SkNf(const __m128& vec) : fVec(vec) {}
 
     SkNf() {}
-    explicit SkNf(float val)           : fVec( _mm_set1_ps(val) ) {}
+    SkNf(float val)           : fVec( _mm_set1_ps(val) ) {}
     static SkNf Load(const float vals[4]) { return _mm_loadu_ps(vals); }
 
     static SkNf FromBytes(const uint8_t bytes[4]) {
@@ -178,7 +178,7 @@ public:
     SkNi(const __m128i& vec) : fVec(vec) {}
 
     SkNi() {}
-    explicit SkNi(uint16_t val) : fVec(_mm_set1_epi16(val)) {}
+    SkNi(uint16_t val) : fVec(_mm_set1_epi16(val)) {}
     static SkNi Load(const uint16_t vals[4]) { return _mm_loadl_epi64((const __m128i*)vals); }
     SkNi(uint16_t a, uint16_t b, uint16_t c, uint16_t d) : fVec(_mm_setr_epi16(a,b,c,d,0,0,0,0)) {}
 
@@ -205,7 +205,7 @@ public:
     SkNi(const __m128i& vec) : fVec(vec) {}
 
     SkNi() {}
-    explicit SkNi(uint16_t val) : fVec(_mm_set1_epi16(val)) {}
+    SkNi(uint16_t val) : fVec(_mm_set1_epi16(val)) {}
     static SkNi Load(const uint16_t vals[8]) { return _mm_loadu_si128((const __m128i*)vals); }
     SkNi(uint16_t a, uint16_t b, uint16_t c, uint16_t d,
          uint16_t e, uint16_t f, uint16_t g, uint16_t h) : fVec(_mm_setr_epi16(a,b,c,d,e,f,g,h)) {}
@@ -247,7 +247,7 @@ public:
     SkNi(const __m128i& vec) : fVec(vec) {}
 
     SkNi() {}
-    explicit SkNi(uint8_t val) : fVec(_mm_set1_epi8(val)) {}
+    SkNi(uint8_t val) : fVec(_mm_set1_epi8(val)) {}
     static SkNi Load(const uint8_t vals[16]) { return _mm_loadu_si128((const __m128i*)vals); }
     SkNi(uint8_t a, uint8_t b, uint8_t c, uint8_t d,
          uint8_t e, uint8_t f, uint8_t g, uint8_t h,