Flip samples to their correct position

SwANGLE tests detected that SwiftShader's sample positions were 180 degree flipped from Vulkan's exact sample locations. Most multisampling tests we've run with SwiftShader so far relied on resolved outputs, so having the samples in the wrong order didn't matter, as long as we had the correct 4 samples (which we do, since the samples are essentially rotated by 90 degrees around the center of the pixel from each other). Bug: b/170962186 Bug: b/141380498 Change-Id: I65552863e1fe38b321b84995e038984488512e1c Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/52088Reviewed-by: Nicolas Capens <nicolascapens@google.com> Tested-by: Alexis Hétu <sugoi@google.com> Commit-Queue: Alexis Hétu <sugoi@google.com> Kokoro-Result: kokoro <noreply+kokoro@google.com>

Flip samples to their correct position
413f7cb1 · Alexis Hetu · swiftshader-scoped@luci-project-accounts.iam.gserviceaccount.com · 3fe96b78 · 413f7cb1 · 413f7cb1
Commit 413f7cb1 authored Jan 22, 2021 by Alexis Hetu Committed by swiftshader-scoped@luci-project-accounts.iam.gserviceaccount.com Jan 22, 2021
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QuadRasterizer.cpp src/Device/QuadRasterizer.cpp +1 -1

PixelRoutine.cpp src/Pipeline/PixelRoutine.cpp +1 -1

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--- a/src/Device/QuadRasterizer.cpp
+++ b/src/Device/QuadRasterizer.cpp
@@ -131,7 +131,7 @@ void QuadRasterizer::rasterize(Int &yMin, Int &yMax)
 				if(state.enableMultiSampling)
 				{
-					y -= *Pointer<Float4>(constants + OFFSET(Constants, Y) + q * sizeof(float4));
+					y += *Pointer<Float4>(constants + OFFSET(Constants, Y) + q * sizeof(float4));
 				}
 				Dz[q] = *Pointer<Float4>(primitive + OFFSET(Primitive, z.C), 16) + y * *Pointer<Float4>(primitive + OFFSET(Primitive, z.B), 16);

--- a/src/Pipeline/PixelRoutine.cpp
+++ b/src/Pipeline/PixelRoutine.cpp
@@ -86,7 +86,7 @@ void PixelRoutine::quad(Pointer<Byte> cBuffer[RENDERTARGETS], Pointer<Byte> &zBu
 			if(state.enableMultiSampling)
 			{
-				x -= *Pointer<Float4>(constants + OFFSET(Constants, X) + q * sizeof(float4));
+				x += *Pointer<Float4>(constants + OFFSET(Constants, X) + q * sizeof(float4));
 			}
 			z[q] = interpolate(x, Dz[q], z[q], primitive + OFFSET(Primitive, z), false, false);