Remove EntryPoint.

This CL removes the EntryPoint node and transitions everything to the
stage decoration.

Change-Id: Ib2840155905c8fa60ff35870f0c4b6705efb73ff
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/28705
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: David Neto <dneto@google.com>
Reviewed-by: Sarah Mashayekhi <sarahmashay@google.com>

test/compute_boids.wgsl

@@ -21,7 +21,8 @@ import "GLSL.std.450" as std;
 [[location(2)]] var<in> a_pos : vec2<f32>;
 [[builtin(position)]] var<out> gl_Position : vec4<f32>;
 
-fn vtx_main() -> void {
+[[stage(vertex)]]
+fn vert_main() -> void {
   var angle : f32 = -std::atan2(a_particleVel.x, a_particleVel.y);
   var pos : vec2<f32> = vec2<f32>(
       (a_pos.x * std::cos(angle)) - (a_pos.y * std::sin(angle)),
@@ -29,16 +30,15 @@ fn vtx_main() -> void {
   gl_Position = vec4<f32>(pos + a_particlePos, 0.0, 1.0);
   return;
 }
-entry_point vertex as "vert_main" = vtx_main;
 
 # fragment shader
 [[location(0)]] var<out> fragColor : vec4<f32>;
 
+[[stage(fragment)]]
 fn frag_main() -> void {
   fragColor = vec4<f32>(1.0, 1.0, 1.0, 1.0);
   return;
 }
-entry_point fragment as "frag_main" = frag_main;
 
 # compute shader
 type Particle = [[block]] struct {
@@ -67,7 +67,8 @@ type Particles = [[block]] struct {
 [[builtin(global_invocation_id)]] var<in> gl_GlobalInvocationID : vec3<u32>;
 
 # https://github.com/austinEng/Project6-Vulkan-Flocking/blob/master/data/shaders/computeparticles/particle.comp
-fn compute_main() -> void {
+[[stage(compute)]]
+fn comp_main() -> void {
   var index : u32 = gl_GlobalInvocationID.x;
   if (index >= 5) {
     return;
@@ -149,5 +150,3 @@ fn compute_main() -> void {
 
   return;
 }
-entry_point compute as "comp_main" = compute_main;
-

test/cube.wgsl

@@ -12,9 +12,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-entry_point vertex = vtx_main;
-entry_point fragment = frag_main;
-
 # Vertex shader
 type Uniforms = [[block]] struct {
   [[offset(0)]] modelViewProjectionMatrix : mat4x4<f32>;
@@ -27,6 +24,7 @@ type Uniforms = [[block]] struct {
 [[location(0)]] var<out> vtxFragColor : vec4<f32>;
 [[builtin(position)]] var<out> Position : vec4<f32>;
 
+[[stage(vertex)]]
 fn vtx_main() -> void {
    Position = uniforms.modelViewProjectionMatrix * cur_position;
    vtxFragColor = color;
@@ -37,6 +35,7 @@ fn vtx_main() -> void {
 [[location(0)]] var<in> fragColor : vec4<f32>;
 [[location(0)]] var<out> outColor : vec4<f32>;
 
+[[stage(fragment)]]
 fn frag_main() -> void {
   outColor = fragColor;
   return;

test/simple.wgsl

@@ -18,10 +18,10 @@ fn bar() -> void {
   return;
 }
 
+[[stage(fragment)]]
 fn main() -> void {
     var a : vec2<f32> = vec2<f32>();
     gl_FragColor = vec4<f32>(0.4, 0.4, 0.8, 1.0);
     bar();
     return;
 }
-entry_point fragment = main;

test/switch-case-selector-must-have-the-same-type-as-the-selector-expression-2.fail.wgsl

@@ -1,6 +1,6 @@
 # v-switch03: line 7: the case selector values must have the same type as the selector expression
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: i32 = -2;
   switch (a) {

test/switch-case-selector-must-have-the-same-type-as-the-selector-expression.fail.wgsl

@@ -1,6 +1,6 @@
 # v-switch03: line 7: the case selector values must have the same type as the selector expression
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: u32 = 2;
   switch (a) {

test/switch-case-selector-value-must-be-unique.fail.wgsl

@@ -1,7 +1,7 @@
 # v-switch04: line 9: a literal value must not appear more than once in the case selectors for a
 # switch statement: '0'
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: u32 = 2;
   switch (a) {

test/switch-fallthrough-must-not-be-last-stmt-of-last-clause.fail.wgsl

@@ -1,7 +1,7 @@
 # v-switch05: line 9: a fallthrough statement must not appear as the last statement in last clause
 # of a switch
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: i32 = -2;
   switch (a) {

test/switch-must-have-exactly-one-default-clause-2.fail.wgsl

@@ -1,6 +1,6 @@
 # v-0008: line 6: switch statement must have exactly one default clause
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: i32 = 2;
   switch (a) {

test/switch-must-have-exactly-one-default-clause.fail.wgsl

@@ -1,6 +1,6 @@
 # v-0008: line 6: switch statement must have exactly one default clause
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: i32 = 2;
   switch (a) {

test/switch-selector-expression-must-be-scalar-integer-type.fail.wgsl

@@ -1,6 +1,6 @@
 # v-switch01: line 6: switch statement selector expression must be of a scalar integer type
 
-entry_point vertex = main;
+[[stage(vertex)]]
 fn main() -> void {
   var a: f32 = 3.14;
   switch (a) {

test/triangle.wgsl

@@ -21,16 +21,17 @@ const pos : array<vec2<f32>, 3> = array<vec2<f32>, 3>(
 [[builtin(position)]] var<out> Position : vec4<f32>;
 [[builtin(vertex_idx)]] var<in> VertexIndex : i32;
 
+[[stage(vertex)]]
 fn vtx_main() -> void {
   Position = vec4<f32>(pos[VertexIndex], 0.0, 1.0);
   return;
 }
-entry_point vertex as "main" = vtx_main;
 
 # Fragment shader
 [[location(0)]] var<out> outColor : vec4<f32>;
+
+[[stage(fragment)]]
 fn frag_main() -> void {
   outColor = vec4<f32>(1.0, 0.0, 0.0, 1.0);
   return;
 }
-entry_point fragment = frag_main;

test/undefined-variable-global-scope.wgsl

@@ -15,9 +15,9 @@
 # Vertex shader
 var<private> a : i32;
 
+[[stage(vertex)]]
 fn main() -> void {
   a = 2;
   return;
 }
-entry_point vertex as "main" = main;
 

test/undefined-variable-inner-block.wgsl

@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+[[stage(fragment)]]
 fn main() -> void {
     var a : f32 = 2.0;
    { a = 3.14;}
     return;
 }
-entry_point fragment = main;