SIMD implementation of Convolver for Lanczos filter etc.

skia/ext/convolver.h

Index: skia/ext/convolver.h
diff --git a/skia/ext/convolver.h b/skia/ext/convolver.h
index 04d6fe5c52db2e05218b8973c5e90b944e0b5d8f..a93dece7815325ba5c104ae169c3ac0c73568ed8 100644
--- a/skia/ext/convolver.h
+++ b/skia/ext/convolver.h
@@ -10,6 +10,7 @@
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/cpu.h"
 
 // avoid confusion with Mac OS X's math library (Carbon)
 #if defined(__APPLE__)
@@ -98,6 +99,13 @@ class ConvolutionFilter1D {
     return &filter_values_[filter.data_location];
   }
 
+  inline void PaddingForSIMD(int align) {

[brettw, 2011/02/21 04:45:45]

I would have thought that you'd want to pad up to the next multiple of the
alignment. If you have 9 things in the filter, do you really just want to leave
it at that, or do you want to pad to 16?

[jiesun, 2011/02/22 21:37:03]

padding in SIMD serve two purpose:
1. make element align to element size boundary, such as 16 or 8.
2. prevent SIMD load and store instruction to access violation.
here I only try to solve problem (2). therefore only padding once after all
filters are added.
solving (1) need to padding for each filters ( not a big deal). but because of
current implementation use <vector> and it is tricky to align at the beginning.

+    // Padding more coefficients to allow SIMD to load after the last one.
+    // This has to be done after all |AddFilter| calls.
+    for (int i = 0; i < align; ++i)
+      filter_values_.push_back(static_cast<Fixed>(0));
+  }
+
  private:
   struct FilterInstance {
     // Offset within filter_values for this instance of the filter.
@@ -148,6 +156,21 @@ void BGRAConvolve2D(const unsigned char* source_data,
                     int output_byte_row_stride,
                     unsigned char* output);
 
+void BGRAConvolve2D_C(const unsigned char* source_data,
+                    int source_byte_row_stride,

[brettw, 2011/02/21 04:45:45]

Style: be sure to align the args in these two functions to after the (

[jiesun, 2011/02/22 21:37:03]

Done.

+                    bool source_has_alpha,
+                    const ConvolutionFilter1D& filter_x,
+                    const ConvolutionFilter1D& filter_y,
+                    int output_byte_row_stride,
+                    unsigned char* output);
+
+void BGRAConvolve2D_SSE2(const unsigned char* source_data,
+                    int source_byte_row_stride,
+                    bool source_has_alpha,
+                    const ConvolutionFilter1D& filter_x,
+                    const ConvolutionFilter1D& filter_y,
+                    int output_byte_row_stride,
+                    unsigned char* output);
 }  // namespace skia
 
 #endif  // SKIA_EXT_CONVOLVER_H_