Add SPIR-V support for modf intrinsic.

Change-Id: I887e700a7bf11bf2d5359c9721798f72f00e53f3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/342756
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>

gn/sksl_tests.gni

@@ -245,6 +245,7 @@ sksl_shared_tests = [
   "$_tests/sksl/intrinsics/Min.sksl",
   "$_tests/sksl/intrinsics/Mix.sksl",
   "$_tests/sksl/intrinsics/Mod.sksl",
+  "$_tests/sksl/intrinsics/Modf.sksl",
   "$_tests/sksl/intrinsics/Normalize.sksl",
   "$_tests/sksl/intrinsics/Not.sksl",
   "$_tests/sksl/intrinsics/NotEqual.sksl",

src/sksl/SkSLSPIRVCodeGenerator.cpp

@@ -72,6 +72,7 @@ void SPIRVCodeGenerator::setupIntrinsics() {
     fIntrinsicMap[String("determinant")]   = ALL_GLSL(Determinant);
     fIntrinsicMap[String("matrixInverse")] = ALL_GLSL(MatrixInverse);
     fIntrinsicMap[String("mod")]           = SPECIAL(Mod);
+    fIntrinsicMap[String("modf")]          = ALL_GLSL(Modf);
     fIntrinsicMap[String("min")]           = SPECIAL(Min);
     fIntrinsicMap[String("max")]           = SPECIAL(Max);
     fIntrinsicMap[String("clamp")]         = SPECIAL(Clamp);

tests/sksl/intrinsics/Modf.sksl

@@ -0,0 +1 @@
+in half a, b; void main() { sk_FragColor.x = modf(a, b); }

tests/sksl/intrinsics/golden/Modf.asm.frag

@@ -0,0 +1,41 @@
+OpCapability Shader
+%1 = OpExtInstImport "GLSL.std.450"
+OpMemoryModel Logical GLSL450
+OpEntryPoint Fragment %main "main" %sk_FragColor %sk_Clockwise %a %b
+OpExecutionMode %main OriginUpperLeft
+OpName %sk_FragColor "sk_FragColor"
+OpName %sk_Clockwise "sk_Clockwise"
+OpName %a "a"
+OpName %b "b"
+OpName %main "main"
+OpDecorate %sk_FragColor RelaxedPrecision
+OpDecorate %sk_FragColor Location 0
+OpDecorate %sk_FragColor Index 0
+OpDecorate %sk_Clockwise RelaxedPrecision
+OpDecorate %sk_Clockwise BuiltIn FrontFacing
+OpDecorate %a RelaxedPrecision
+OpDecorate %b RelaxedPrecision
+OpDecorate %17 RelaxedPrecision
+%float = OpTypeFloat 32
+%v4float = OpTypeVector %float 4
+%_ptr_Output_v4float = OpTypePointer Output %v4float
+%sk_FragColor = OpVariable %_ptr_Output_v4float Output
+%bool = OpTypeBool
+%_ptr_Input_bool = OpTypePointer Input %bool
+%sk_Clockwise = OpVariable %_ptr_Input_bool Input
+%_ptr_Input_float = OpTypePointer Input %float
+%a = OpVariable %_ptr_Input_float Input
+%b = OpVariable %_ptr_Input_float Input
+%void = OpTypeVoid
+%14 = OpTypeFunction %void
+%_ptr_Output_float = OpTypePointer Output %float
+%int = OpTypeInt 32 1
+%int_0 = OpConstant %int 0
+%main = OpFunction %void None %14
+%15 = OpLabel
+%17 = OpLoad %float %a
+%16 = OpExtInst %float %1 Modf %17 %b
+%18 = OpAccessChain %_ptr_Output_float %sk_FragColor %int_0
+OpStore %18 %16
+OpReturn
+OpFunctionEnd

tests/sksl/intrinsics/golden/Modf.glsl

@@ -0,0 +1,7 @@
+
+out vec4 sk_FragColor;
+in float a;
+in float b;
+void main() {
+    sk_FragColor.x = modf(a, b);
+}

tests/sksl/intrinsics/golden/Modf.metal

@@ -0,0 +1,24 @@
+#include <metal_stdlib>
+#include <simd/simd.h>
+using namespace metal;
+struct Inputs {
+    float a;
+    float b;
+};
+struct Outputs {
+    float4 sk_FragColor [[color(0)]];
+};
+float _skOutParamHelper0_modf(float _var0, thread float& b) {
+    float _var1;
+    float _skResult = modf(_var0, _var1);
+    b = _var1;
+    return _skResult;
+}
+
+
+fragment Outputs fragmentMain(Inputs _in [[stage_in]], bool _frontFacing [[front_facing]], float4 _fragCoord [[position]]) {
+    Outputs _outputStruct;
+    thread Outputs* _out = &_outputStruct;
+    _out->sk_FragColor.x =     _skOutParamHelper0_modf(_in.a, _in.b);
+    return *_out;
+}