VkPipeline: Fix unsigned integer underflows in computePrimitiveCount()

Tests: dEQP-VK.draw.basic_draw.* Change-Id: I609e22601c4aae1bdebaca6d42d33754cfaa57bb Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/31840 Presubmit-Ready: Ben Clayton <bclayton@google.com> Tested-by: Ben Clayton <bclayton@google.com> Reviewed-by: Alexis Hétu <sugoi@google.com> Reviewed-by: Chris Forbes <chrisforbes@google.com> Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>

VkPipeline: Fix unsigned integer underflows in computePrimitiveCount()
9b843ea8 · Ben Clayton · c367b22b · 9b843ea8
Commit 9b843ea8 authored May 23, 2019 by Ben Clayton
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VkPipeline.cpp src/Vulkan/VkPipeline.cpp +3 -3

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--- a/src/Vulkan/VkPipeline.cpp
+++ b/src/Vulkan/VkPipeline.cpp
@@ -485,13 +485,13 @@ uint32_t GraphicsPipeline::computePrimitiveCount(uint32_t vertexCount) const
 	case VK_PRIMITIVE_TOPOLOGY_LINE_LIST:
 		return vertexCount / 2;
 	case VK_PRIMITIVE_TOPOLOGY_LINE_STRIP:
-		return vertexCount - 1;
+		return std::max<uint32_t>(vertexCount, 1) - 1;
 	case VK_PRIMITIVE_TOPOLOGY_TRIANGLE_LIST:
 		return vertexCount / 3;
 	case VK_PRIMITIVE_TOPOLOGY_TRIANGLE_STRIP:
-		return vertexCount - 2;
+		return std::max<uint32_t>(vertexCount, 2) - 2;
 	case VK_PRIMITIVE_TOPOLOGY_TRIANGLE_FAN:
-		return vertexCount - 2;
+		return std::max<uint32_t>(vertexCount, 2) - 2;
 	default:
 		UNIMPLEMENTED("context.topology %d", int(context.topology));
 	}