Add unit test for control statements in while loops.

Change-Id: I924ac75b5f8a397f7af7a06925ef0c9deba5c509
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/359141
Commit-Queue: John Stiles <johnstiles@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>

gn/sksl_tests.gni

@@ -384,6 +384,7 @@ sksl_shared_tests = [
   "/sksl/shared/VectorConstructors.sksl",
   "/sksl/shared/VertexEarlyReturn.vert",
   "/sksl/shared/VertexID.vert",
+  "/sksl/shared/WhileLoopControlFlow.sksl",
   "/sksl/shared/Width.sksl",
 ]
 

resources/sksl/shared/WhileLoopControlFlow.sksl

@@ -0,0 +1,19 @@
+half4 main() {
+    half4 x = half4(1, 1, 1, 1);
+
+    // Verify that break is allowed in a while loop.
+    while (x.a == 1) {
+        x.r -= 0.25;
+        if (x.r <= 0) break;
+    }
+
+    // Verify that continue is allowed in a while loop.
+    while (x.b > 0) {
+        x.b -= 0.25;
+        if (x.a == 1) continue; // should always happen
+        x.g = 0;
+    }
+
+    // x contains green.
+    return x;
+}

tests/sksl/shared/WhileLoopControlFlow.asm.frag

@@ -0,0 +1,103 @@
+### Compilation failed:
+
+error: SPIR-V validation error: OpEntryPoint Entry Point <id> '2[%main]'s function return type is not void.
+  OpEntryPoint Fragment %main "main" %sk_Clockwise
+
+OpCapability Shader
+%1 = OpExtInstImport "GLSL.std.450"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main" %sk_Clockwise
+OpExecutionMode %main OriginUpperLeft
+OpName %sk_Clockwise "sk_Clockwise"
+OpName %main "main"
+OpName %x "x"
+OpDecorate %sk_Clockwise RelaxedPrecision
+OpDecorate %sk_Clockwise BuiltIn FrontFacing
+OpDecorate %19 RelaxedPrecision
+OpDecorate %26 RelaxedPrecision
+OpDecorate %28 RelaxedPrecision
+OpDecorate %29 RelaxedPrecision
+OpDecorate %40 RelaxedPrecision
+OpDecorate %45 RelaxedPrecision
+OpDecorate %46 RelaxedPrecision
+OpDecorate %47 RelaxedPrecision
+OpDecorate %54 RelaxedPrecision
+%bool = OpTypeBool
+%_ptr_Input_bool = OpTypePointer Input %bool
+%sk_Clockwise = OpVariable %_ptr_Input_bool Input
+%float = OpTypeFloat 32
+%v4float = OpTypeVector %float 4
+%8 = OpTypeFunction %v4float
+%_ptr_Function_v4float = OpTypePointer Function %v4float
+%float_1 = OpConstant %float 1
+%13 = OpConstantComposite %v4float %float_1 %float_1 %float_1 %float_1
+%_ptr_Function_float = OpTypePointer Function %float
+%int = OpTypeInt 32 1
+%int_0 = OpConstant %int 0
+%float_0_25 = OpConstant %float 0.25
+%float_0 = OpConstant %float 0
+%int_2 = OpConstant %int 2
+%int_1 = OpConstant %int 1
+%main = OpFunction %v4float None %8
+%9 = OpLabel
+%x = OpVariable %_ptr_Function_v4float Function
+OpStore %x %13
+OpBranch %14
+%14 = OpLabel
+OpLoopMerge %18 %17 None
+OpBranch %15
+%15 = OpLabel
+%19 = OpLoad %v4float %x
+%20 = OpCompositeExtract %float %19 3
+%21 = OpFOrdEqual %bool %20 %float_1
+OpBranchConditional %21 %16 %18
+%16 = OpLabel
+%22 = OpAccessChain %_ptr_Function_float %x %int_0
+%26 = OpLoad %float %22
+%28 = OpFSub %float %26 %float_0_25
+OpStore %22 %28
+%29 = OpLoad %v4float %x
+%30 = OpCompositeExtract %float %29 0
+%32 = OpFOrdLessThanEqual %bool %30 %float_0
+OpSelectionMerge %34 None
+OpBranchConditional %32 %33 %34
+%33 = OpLabel
+OpBranch %18
+%34 = OpLabel
+OpBranch %17
+%17 = OpLabel
+OpBranch %14
+%18 = OpLabel
+OpBranch %35
+%35 = OpLabel
+OpLoopMerge %39 %38 None
+OpBranch %36
+%36 = OpLabel
+%40 = OpLoad %v4float %x
+%41 = OpCompositeExtract %float %40 2
+%42 = OpFOrdGreaterThan %bool %41 %float_0
+OpBranchConditional %42 %37 %39
+%37 = OpLabel
+%43 = OpAccessChain %_ptr_Function_float %x %int_2
+%45 = OpLoad %float %43
+%46 = OpFSub %float %45 %float_0_25
+OpStore %43 %46
+%47 = OpLoad %v4float %x
+%48 = OpCompositeExtract %float %47 3
+%49 = OpFOrdEqual %bool %48 %float_1
+OpSelectionMerge %51 None
+OpBranchConditional %49 %50 %51
+%50 = OpLabel
+OpBranch %38
+%51 = OpLabel
+%52 = OpAccessChain %_ptr_Function_float %x %int_1
+OpStore %52 %float_0
+OpBranch %38
+%38 = OpLabel
+OpBranch %35
+%39 = OpLabel
+%54 = OpLoad %v4float %x
+OpReturnValue %54
+OpFunctionEnd
+
+1 error

tests/sksl/shared/WhileLoopControlFlow.glsl

@@ -0,0 +1,14 @@
+
+vec4 main() {
+    vec4 x = vec4(1.0, 1.0, 1.0, 1.0);
+    while (x.w == 1.0) {
+        x.x -= 0.25;
+        if (x.x <= 0.0) break;
+    }
+    while (x.z > 0.0) {
+        x.z -= 0.25;
+        if (x.w == 1.0) continue;
+        x.y = 0.0;
+    }
+    return x;
+}

tests/sksl/shared/WhileLoopControlFlow.metal

@@ -0,0 +1,24 @@
+#include <metal_stdlib>
+#include <simd/simd.h>
+using namespace metal;
+struct Inputs {
+};
+struct Outputs {
+    float4 sk_FragColor [[color(0)]];
+};
+fragment Outputs fragmentMain(Inputs _in [[stage_in]], bool _frontFacing [[front_facing]], float4 _fragCoord [[position]]) {
+    Outputs _out;
+    (void)_out;
+    float4 x = float4(1.0, 1.0, 1.0, 1.0);
+    while (x.w == 1.0) {
+        x.x = x.x - 0.25;
+        if (x.x <= 0.0) break;
+    }
+    while (x.z > 0.0) {
+        x.z = x.z - 0.25;
+        if (x.w == 1.0) continue;
+        x.y = 0.0;
+    }
+    _out.sk_FragColor = x;
+    return _out;
+}