commit e8ce1f839b1f5a7c4e5b97c89c8e22bfbac40ff4
author Nicolas Capens <capn@google.com> Thu Oct 08 11:12:20 2020 -0400
committer Nicolas Capens <nicolascapens@google.com> Fri Oct 09 17:46:41 2020 +0000
tree 1bf6b20a0ae6f7deab269bf40f18b374fa2b2725
parent 51b03d58fb17b09120c886d5df36fb191d12fa8e

Move interpolant clamping out of interpolate()

Vulkan never clamps interpolants, except for depth values (specifically
for fixed-point formats, and for floating-point formats when the
unrestricted depth extension is not enabled).

This change moves the clamping operation out of interpolate(), which
makes it easier to see depth clamping being performed when necessary,
and will facilitate changes in applying depth bias.

Bug: b/139341727
Change-Id: I8cef29d63fef00308ef2f813b4feb687c83baa86
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/49148
Presubmit-Ready: Nicolas Capens <nicolascapens@google.com>
Kokoro-Result: kokoro <noreply+kokoro@google.com>
Tested-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Sean Risser <srisser@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>

src/Device/QuadRasterizer.cpp

diff --git a/src/Device/QuadRasterizer.cpp b/src/Device/QuadRasterizer.cpp
index 389b81a..62f2253 100644
--- a/src/Device/QuadRasterizer.cpp
+++ b/src/Device/QuadRasterizer.cpp
@@ -231,7 +231,7 @@
 	Until(y >= yMax);
 }
 
-Float4 QuadRasterizer::interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective, bool clamp)
+Float4 QuadRasterizer::interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective)
 {
 	Float4 interpolant = D;
 
@@ -245,11 +245,6 @@
 		}
 	}
 
-	if(clamp)
-	{
-		interpolant = Min(Max(interpolant, Float4(0.0f)), Float4(1.0f));
-	}
-
 	return interpolant;
 }
 

src/Device/QuadRasterizer.hpp

diff --git a/src/Device/QuadRasterizer.hpp b/src/Device/QuadRasterizer.hpp
index f24e80e..2f19d1d 100644
--- a/src/Device/QuadRasterizer.hpp
+++ b/src/Device/QuadRasterizer.hpp
@@ -46,7 +46,7 @@
 
 	bool interpolateZ() const;
 	bool interpolateW() const;
-	Float4 interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective, bool clamp);
+	Float4 interpolate(Float4 &x, Float4 &D, Float4 &rhw, Pointer<Byte> planeEquation, bool flat, bool perspective);
 
 	const PixelProcessor::State &state;
 	const SpirvShader *const spirvShader;

src/Pipeline/PixelRoutine.cpp

diff --git a/src/Pipeline/PixelRoutine.cpp b/src/Pipeline/PixelRoutine.cpp
index 7d9f349..dc27e90 100644
--- a/src/Pipeline/PixelRoutine.cpp
+++ b/src/Pipeline/PixelRoutine.cpp
@@ -90,7 +90,12 @@
 				x -= *Pointer<Float4>(constants + OFFSET(Constants, X) + q * sizeof(float4));
 			}
 
-			z[q] = interpolate(x, Dz[q], z[q], primitive + OFFSET(Primitive, z), false, false, state.depthClamp);
+			z[q] = interpolate(x, Dz[q], z[q], primitive + OFFSET(Primitive, z), false, false);
+
+			if(state.depthClamp)
+			{
+				z[q] = Min(Max(z[q], Float4(0.0f)), Float4(1.0f));
+			}
 		}
 	}
 
@@ -133,7 +138,7 @@
 
 		if(interpolateW())
 		{
-			w = interpolate(xxxx, Dw, rhw, primitive + OFFSET(Primitive, w), false, false, false);
+			w = interpolate(xxxx, Dw, rhw, primitive + OFFSET(Primitive, w), false, false);
 			rhw = reciprocal(w, false, false, true);
 
 			if(state.centroid)
@@ -161,7 +166,7 @@
 						routine.inputs[interpolant] =
 						    interpolate(xxxx, Dv[interpolant], rhw,
 						                primitive + OFFSET(Primitive, V[interpolant]),
-						                input.Flat, !input.NoPerspective, false);
+						                input.Flat, !input.NoPerspective);
 					}
 				}
 			}
@@ -172,7 +177,7 @@
 			{
 				auto distance = interpolate(xxxx, DclipDistance[i], rhw,
 				                            primitive + OFFSET(Primitive, clipDistance[i]),
-				                            false, true, false);
+				                            false, true);
 
 				auto clipMask = SignMask(CmpGE(distance, SIMD::Float(0)));
 				for(auto ms = 0u; ms < state.multiSampleCount; ms++)
@@ -208,7 +213,7 @@
 							routine.getVariable(it->second.Id)[it->second.FirstComponent + i] =
 							    interpolate(xxxx, DcullDistance[i], rhw,
 							                primitive + OFFSET(Primitive, cullDistance[i]),
-							                false, true, false);
+							                false, true);
 						}
 					}
 				}