Manually set fFilterValues in SkConvolutionFilter1D.

Using fFilterValues.reset() or a loop of fFilterValues.push_back() is about 5x slower than calling fFilterValues.resize_back() and then looping using primitive [] and =.

This is only going to show up if you apply https://codereview.chromium.org/183763047/, where it yields about 2.5% speedup in the bitmap resize microbenchmarks on a Linux desktop. Ceteris paribus, it should actually improve rasterization time of drawBitmapRectToRect() with a resize by about 5% in Chromium.

BUG=skia:2258
R=humper@google.com, tomhudson@google.com

Author: tomhudson@chromium.org

Review URL: https://codereview.chromium.org/184323003

git-svn-id: http://skia.googlecode.com/svn/trunk@13681 2bbb7eff-a529-9590-31e7-b0007b416f81

diff --git a/src/core/SkConvolver.cpp b/src/core/SkConvolver.cpp
index 7666e6f..e26c8e7 100644 (file)
--- a/src/core/SkConvolver.cpp
+++ b/src/core/SkConvolver.cpp
@@ -294,8 +294,10 @@ void SkConvolutionFilter1D::AddFilter(int filterOffset,
         filterLength = lastNonZero + 1 - firstNonZero;
         SkASSERT(filterLength > 0);
 
+        // Calling fFilterValues.reset(), or push_back() in a loop, are expensive.
+        fFilterValues.resize_back(filterLength);
         for (int i = firstNonZero; i <= lastNonZero; i++) {
-            fFilterValues.push_back(filterValues[i]);
+            fFilterValues[i - firstNonZero] = filterValues[i];
         }
     } else {
         // Here all the factors were zeroes.