HLSL: support point mode.

Test/hlsl.hull.3.tesc

@@ -0,0 +1,39 @@
+// *** 
+// invocation ID coming from synthesized variable
+// ***
+
+struct VS_OUT
+{
+    float3 cpoint : CPOINT;
+};
+
+struct HS_CONSTANT_OUT
+{
+    float edges[2] : SV_TessFactor;
+};
+
+struct HS_OUT
+{
+    float3 cpoint : CPOINT;
+};
+
+[domain("tri")]
+[partitioning("integer")]
+[outputtopology("point")]
+[outputcontrolpoints(4)]
+[patchconstantfunc("PCF")]
+HS_OUT main(InputPatch<VS_OUT, 4> ip)
+{
+    HS_OUT output;
+    output.cpoint = ip[0].cpoint;
+    return output;
+}
+
+HS_CONSTANT_OUT PCF(uint pid : SV_PrimitiveId, float4 pos : SV_Position)
+{
+    HS_CONSTANT_OUT output;
+    
+    output.edges[0] = 2.0f;
+    output.edges[1] = 8.0f;
+    return output;
+}