Streamline GrGradientEffect mirror tiling

Using the same branch-less method as raster pipeline.

Change-Id: Iaaa36330dbf49961bdfc288cad031d891d8ff589
Reviewed-on: https://skia-review.googlesource.com/31280
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>

1 files changed, 2 insertions, 10 deletions

diff --git a/src/shaders/gradients/SkGradientShader.cpp b/src/shaders/gradients/SkGradientShader.cpp
index 4fcfa36d85..186f683dca 100644
--- a/src/shaders/gradients/SkGradientShader.cpp
+++ b/src/shaders/gradients/SkGradientShader.cpp
@@ -1567,16 +1567,8 @@ void GrGradientEffect::GLSLProcessor::emitAnalyticalColor(GrGLSLFPFragmentBuilde
         }
         break;
     case SkShader::kMirror_TileMode:
-        fragBuilder->codeAppendf("float clamp_t = %s;", t);
-        // TODO: Is this conditional really useful?  Since the client requested kMirror,
-        // t is likely outside [0,1] most of the time so we might as well always fall through.
-        fragBuilder->codeAppendf("if (%s < 0.0 || %s > 1.0) {", t, t);
-        fragBuilder->codeAppendf("    if (mod(floor(%s), 2.0) == 0.0) {", t);
-        fragBuilder->codeAppendf("        clamp_t = fract(%s);", t);
-        fragBuilder->codeAppendf("    } else {");
-        fragBuilder->codeAppendf("        clamp_t = 1.0 - fract(%s);", t);
-        fragBuilder->codeAppendf("    }");
-        fragBuilder->codeAppendf("}");
+        fragBuilder->codeAppendf("float t_1 = %s - 1.0;", t);
+        fragBuilder->codeAppendf("float clamp_t = abs(t_1 - 2.0 * floor(t_1 * 0.5) - 1.0);");
         break;
     }