Replace Shader,VertexShader,PixelShader with SpirvShader

Also deletes tons of fixed-function-centric stuff that will never be
used by the Vulkan backend. Very little of the SPIRV integration
actually does anything interesting yet (we don't generate code) but this
wires on the new shader representation.

Bug: b/120799499

Change-Id: Ib76e2086113098aebd526a0da461689d4344e8c2
Reviewed-on: https://swiftshader-review.googlesource.com/c/23090
Tested-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

src/Device/QuadRasterizer.cpp

diff --git a/src/Device/QuadRasterizer.cpp b/src/Device/QuadRasterizer.cpp
index 90d560d..237c9e3 100644
--- a/src/Device/QuadRasterizer.cpp
+++ b/src/Device/QuadRasterizer.cpp
@@ -28,7 +28,7 @@
 
 	extern int clusterCount;
 
-	QuadRasterizer::QuadRasterizer(const PixelProcessor::State &state, const PixelShader *pixelShader) : state(state), shader(pixelShader)
+	QuadRasterizer::QuadRasterizer(const PixelProcessor::State &state, SpirvShader const *spirvShader) : state(state), spirvShader{spirvShader}
 	{
 	}
 
@@ -340,11 +340,11 @@
 
 	bool QuadRasterizer::interpolateZ() const
 	{
-		return state.depthTestActive || (shader && shader->isVPosDeclared() && fullPixelPositionRegister);
+		return state.depthTestActive || (spirvShader && spirvShader->hasBuiltinInput(spv::BuiltInPosition));
 	}
 
 	bool QuadRasterizer::interpolateW() const
 	{
-		return state.perspective || (shader && shader->isVPosDeclared() && fullPixelPositionRegister);
+		return state.perspective || (spirvShader && spirvShader->hasBuiltinInput(spv::BuiltInPosition));
 	}
 }