MSL: Return early from helper tesc invocations.

Return after loading the input control point array if there are more
input points than output points, and this was one of the helper
invocations spun off to load the input points. I was hesitant to do this
initially, since the MSL spec has this to say about barriers:

> The `threadgroup_barrier` (or `simdgroup_barrier`) function must be
> encountered by all threads in a threadgroup (or SIMD-group) executing
> the kernel.

That is, if any thread executes the barrier, then all threads must
execute it, or the barrier'd invocations will hang. But, the key words
here seem to be "executing the kernel;" inactive invocations, those that
have already returned, need not encounter the barrier to prevent hangs.
Indeed, I've encountered no problems from doing this, at least on my
hardware. This also fixes a few CTS tests that were failing due to
execution ordering; apparently, my assumption that the later, invalid
data written by the helpers would get overwritten was wrong.

reference/opt/shaders-msl/asm/tesc/tess-fixed-input-array-builtin-array.invalid.asm.tesc

@@ -52,6 +52,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 3)
+        return;
     VertexOutput _223[3] = { VertexOutput{ gl_in[0].gl_Position, gl_in[0].VertexOutput_uv }, VertexOutput{ gl_in[1].gl_Position, gl_in[1].VertexOutput_uv }, VertexOutput{ gl_in[2].gl_Position, gl_in[2].VertexOutput_uv } };
     VertexOutput param[3];
     spvArrayCopyFromStack1(param, _223);

reference/opt/shaders-msl/desktop-only/tesc/arrayed-output.desktop.sso.tesc

@@ -25,6 +25,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 4)
+        return;
     gl_out[gl_InvocationID].vVertex = gl_in[gl_InvocationID].vInput + gl_in[gl_InvocationID ^ 1].vInput;
     threadgroup_barrier(mem_flags::mem_device);
     if (gl_InvocationID == 0)

reference/opt/shaders-msl/desktop-only/tesc/basic.desktop.sso.tesc

@@ -25,6 +25,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 1)
+        return;
     spvTessLevel[gl_PrimitiveID].insideTessellationFactor[0] = half(8.8999996185302734375);
     spvTessLevel[gl_PrimitiveID].insideTessellationFactor[1] = half(6.900000095367431640625);
     spvTessLevel[gl_PrimitiveID].edgeTessellationFactor[0] = half(8.8999996185302734375);

reference/opt/shaders-msl/desktop-only/tesc/struct-copy.desktop.sso.tesc

@@ -26,6 +26,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 4)
+        return;
     Boo vInput_24;
     vInput_24.a = gl_in[gl_InvocationID].Boo_a;
     vInput_24.b = gl_in[gl_InvocationID].Boo_b;

reference/opt/shaders-msl/tesc/water_tess.tesc

@@ -30,6 +30,8 @@ kernel void main0(main0_in in [[stage_in]], constant UBO& _41 [[buffer(0)]], uin
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 1)
+        return;
     float2 _430 = (gl_in[0].vPatchPosBase - float2(10.0)) * _41.uScale.xy;
     float2 _440 = ((gl_in[0].vPatchPosBase + _41.uPatchSize) + float2(10.0)) * _41.uScale.xy;
     float3 _445 = float3(_430.x, -10.0, _430.y);

reference/shaders-msl/asm/tesc/tess-fixed-input-array-builtin-array.invalid.asm.tesc

@@ -82,6 +82,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 3)
+        return;
     VertexOutput p[3];
     p[0].pos = gl_in[0].gl_Position;
     p[0].uv = gl_in[0].VertexOutput_uv;

reference/shaders-msl/desktop-only/tesc/arrayed-output.desktop.sso.tesc

@@ -25,6 +25,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 4)
+        return;
     gl_out[gl_InvocationID].vVertex = gl_in[gl_InvocationID].vInput + gl_in[gl_InvocationID ^ 1].vInput;
     threadgroup_barrier(mem_flags::mem_device);
     if (gl_InvocationID == 0)

reference/shaders-msl/desktop-only/tesc/basic.desktop.sso.tesc

@@ -32,6 +32,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 1)
+        return;
     spvTessLevel[gl_PrimitiveID].insideTessellationFactor[0] = half(8.8999996185302734375);
     spvTessLevel[gl_PrimitiveID].insideTessellationFactor[1] = half(6.900000095367431640625);
     spvTessLevel[gl_PrimitiveID].edgeTessellationFactor[0] = half(8.8999996185302734375);

reference/shaders-msl/desktop-only/tesc/struct-copy.desktop.sso.tesc

@@ -26,6 +26,8 @@ kernel void main0(main0_in in [[stage_in]], uint gl_InvocationID [[thread_index_
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 4)
+        return;
     Boo vInput_24;
     vInput_24.a = gl_in[gl_InvocationID].Boo_a;
     vInput_24.b = gl_in[gl_InvocationID].Boo_b;

reference/shaders-msl/tesc/water_tess.tesc

@@ -112,6 +112,8 @@ kernel void main0(main0_in in [[stage_in]], constant UBO& v_41 [[buffer(0)]], ui
     if (gl_InvocationID < spvIndirectParams[0])
         gl_in[gl_InvocationID] = in;
     threadgroup_barrier(mem_flags::mem_threadgroup);
+    if (gl_InvocationID >= 1)
+        return;
     float2 p0 = gl_in[0].vPatchPosBase;
     float2 param = p0;
     if (!frustum_cull(param, v_41))

spirv_msl.cpp

@@ -1796,6 +1796,8 @@ uint32_t CompilerMSL::add_interface_block(StorageClass storage, bool patch)
 				statement("    ", input_wg_var_name, "[", to_expression(builtin_invocation_id_id), "] = ", ib_var_ref,
 				          ";");
 				statement("threadgroup_barrier(mem_flags::mem_threadgroup);");
+				statement("if (", to_expression(builtin_invocation_id_id), " >= ", get_entry_point().output_vertices, ")");
+				statement("    return;");
 			});
 		}
 		break;