Clipper: Avoid dynamic allocations
The triangle clipper was allocating its temporary input, output and work buffers using a std::vector. Since this is a hot path, it's desirable to use stack allocation instead.
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Subproject commit b060148c08ae87a3a5809c4f48cb26ac667487ab
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Subproject commit 97052c28acb141dbf3c5e14114af99045344b695
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@ -2,7 +2,7 @@
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#include <vector>
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#include <boost/container/static_vector.hpp>
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#include "clipper.h"
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#include "pica.h"
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@ -98,18 +98,15 @@ static void InitScreenCoordinates(OutputVertex& vtx)
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}
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void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
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using boost::container::static_vector;
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// TODO (neobrain):
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// The list of output vertices has some fixed maximum size,
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// however I haven't taken the time to figure out what it is exactly.
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// For now, we hence just assume a maximal size of 1000 vertices.
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const size_t max_vertices = 1000;
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std::vector<OutputVertex> buffer_vertices;
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std::vector<OutputVertex*> output_list{ &v0, &v1, &v2 };
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// Make sure to reserve space for all vertices.
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// Without this, buffer reallocation would invalidate references.
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buffer_vertices.reserve(max_vertices);
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// For now, we hence just assume a maximal size of 256 vertices.
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static const size_t MAX_VERTICES = 256;
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static_vector<OutputVertex, MAX_VERTICES> buffer_vertices;
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static_vector<OutputVertex*, MAX_VERTICES> output_list = { &v0, &v1, &v2 };
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// Simple implementation of the Sutherland-Hodgman clipping algorithm.
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// TODO: Make this less inefficient (currently lots of useless buffering overhead happens here)
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@ -120,7 +117,7 @@ void ProcessTriangle(OutputVertex &v0, OutputVertex &v1, OutputVertex &v2) {
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ClippingEdge(ClippingEdge::POS_Z, float24::FromFloat32(+1.0)),
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ClippingEdge(ClippingEdge::NEG_Z, float24::FromFloat32(-1.0)) }) {
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const std::vector<OutputVertex*> input_list = output_list;
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const static_vector<OutputVertex*, MAX_VERTICES> input_list = output_list;
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output_list.clear();
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const OutputVertex* reference_vertex = input_list.back();
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