Add a test runtime effect for child effects.

I wasn't able to find any other test which exercised child color-filters
or child blenders. (SampleWithExplicitCoord evaluates from a shader.)

Change-Id: I58ecee3beca2d3dc11ded5de0eea031e1d7c3e1e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/507922
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Commit-Queue: Arman Uguray <armansito@google.com>

gn/sksl_tests.gni

@@ -632,6 +632,7 @@ sksl_rte_tests = [
   "/sksl/runtime/ArrayIndexing.rts",
   "/sksl/runtime/ArrayNarrowingConversions.rts",
   "/sksl/runtime/Blend.rtb",
+  "/sksl/runtime/ChildEffects.rts",
   "/sksl/runtime/Commutative.rts",
   "/sksl/runtime/ConstPreservation.rts",
   "/sksl/runtime/ConversionConstructors.rts",

resources/sksl/runtime/ChildEffects.rts

@@ -0,0 +1,7 @@
+uniform shader s1, s2;
+uniform colorFilter c1, c2;
+uniform blender b;
+
+half4 main(float2 xy) {
+    return b.eval(c1.eval(s1.eval(xy)), c2.eval(s2.eval(xy)));
+}

tests/sksl/runtime/ChildEffects.skvm

@@ -0,0 +1,45 @@
+15 registers, 43 instructions:
+0	r0 = uniform32 ptr0 0
+1	r1 = uniform32 ptr0 C
+2	r2 = uniform32 ptr0 18
+3	r0 = trunc r0
+4	r1 = mul_i32 r1 r0
+5	r3 = splat 1 (1.4012985e-45)
+6	r4 = splat 2 (2.8025969e-45)
+7	r5 = splat 3 (4.2038954e-45)
+8	r0 = mul_i32 r2 r0
+9	r2 = splat 3F800000 (1)
+loop:
+10	    r6 = index
+11	    r6 = trunc r6
+12	    r7 = add_i32 r6 r1
+13	    r7 = shl_i32 r7 2
+14	    r8 = gather32 ptr0 4 r7
+15	    r9 = add_i32 r7 r3
+16	    r9 = gather32 ptr0 4 r9
+17	    r10 = add_i32 r7 r4
+18	    r10 = gather32 ptr0 4 r10
+19	    r7 = add_i32 r7 r5
+20	    r7 = gather32 ptr0 4 r7
+21	    r6 = add_i32 r6 r0
+22	    r6 = shl_i32 r6 2
+23	    r11 = gather32 ptr0 10 r6
+24	    r12 = add_i32 r3 r6
+25	    r12 = gather32 ptr0 10 r12
+26	    r13 = add_i32 r4 r6
+27	    r13 = gather32 ptr0 10 r13
+28	    r6 = add_i32 r5 r6
+29	    r6 = gather32 ptr0 10 r6
+30	    r14 = sub_f32 r2 r7
+31	    r11 = mul_f32 r11 r14
+32	    r11 = add_f32 r8 r11
+33	    r12 = mul_f32 r12 r14
+34	    r12 = add_f32 r9 r12
+35	    r13 = mul_f32 r13 r14
+36	    r13 = add_f32 r10 r13
+37	    r14 = mul_f32 r6 r14
+38	    r14 = add_f32 r7 r14
+39	    store32 ptr1 r11
+40	    store32 ptr2 r12
+41	    store32 ptr3 r13
+42	    store32 ptr4 r14

tests/sksl/runtime/ChildEffects.stage

@@ -0,0 +1,4 @@
+half4 main(float2 xy)
+{
+	return half4(child_4.eval(child_2.eval(child_0.eval(_coords)), child_3.eval(child_1.eval(_coords))));
+}