add SkVM_fwd.h

Tweaking SkVM.h requires ~550 build steps because SkShaderBase.h
includes it.  By switching that to forward declarations of the types
using SkVM_fwd.h, it's down to ~15.  Big deal for laptop productivity.

Change-Id: Ide5cc776b8a0c6fa6473cf5f43acabdf566e8808
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/262860
Commit-Queue: Mike Klein <mtklein@google.com>
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Reed <reed@google.com>

gn/core.gni

@@ -400,6 +400,7 @@ skia_core_sources = [
   "$_src/core/SkUtils.h",
   "$_src/core/SkVM.cpp",
   "$_src/core/SkVM.h",
+  "$_src/core/SkVM_fwd.h",
   "$_src/core/SkVMBlitter.cpp",
   "$_src/core/SkValidationUtils.h",
   "$_src/core/SkVertices.cpp",

src/core/SkColorFilter_Matrix.cpp

@@ -14,6 +14,7 @@
 #include "src/core/SkColorFilter_Matrix.h"
 #include "src/core/SkRasterPipeline.h"
 #include "src/core/SkReadBuffer.h"
+#include "src/core/SkVM.h"
 #include "src/core/SkWriteBuffer.h"
 
 static uint16_t ComputeFlags(const float matrix[20]) {

src/core/SkVM.h

@@ -10,6 +10,7 @@
 
 #include "include/core/SkTypes.h"
 #include "include/private/SkTHash.h"
+#include "src/core/SkVM_fwd.h"
 #include <vector>      // std::vector
 
 class SkWStream;
@@ -305,8 +306,6 @@ namespace skvm {
 
     struct Color { skvm::F32 r,g,b,a; };
 
-    class Program;
-
     class Builder {
     public:
         struct Instruction {

src/core/SkVM_fwd.h

@@ -0,0 +1,22 @@
+/*
+ * Copyright 2020 Google LLC
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkVM_fwd_DEFINED
+#define SkVM_fwd_DEFINED
+
+namespace skvm {
+    class Assembler;
+    class Builder;
+    class Program;
+    struct Arg;
+    struct I32;
+    struct F32;
+    struct Color;
+    struct Uniforms;
+}
+
+#endif//SkVM_fwd_DEFINED

src/shaders/SkColorFilterShader.cpp

@@ -10,6 +10,7 @@
 #include "src/core/SkArenaAlloc.h"
 #include "src/core/SkRasterPipeline.h"
 #include "src/core/SkReadBuffer.h"
+#include "src/core/SkVM.h"
 #include "src/core/SkWriteBuffer.h"
 #include "src/shaders/SkColorFilterShader.h"
 

src/shaders/SkColorShader.cpp

@@ -12,6 +12,7 @@
 #include "src/core/SkRasterPipeline.h"
 #include "src/core/SkReadBuffer.h"
 #include "src/core/SkUtils.h"
+#include "src/core/SkVM.h"
 #include "src/shaders/SkColorShader.h"
 
 SkColorShader::SkColorShader(SkColor c) : fColor(c) {}

src/shaders/SkImageShader.cpp

@@ -12,6 +12,7 @@
 #include "src/core/SkOpts.h"
 #include "src/core/SkRasterPipeline.h"
 #include "src/core/SkReadBuffer.h"
+#include "src/core/SkVM.h"
 #include "src/core/SkWriteBuffer.h"
 #include "src/image/SkImage_Base.h"
 #include "src/shaders/SkBitmapProcShader.h"

src/shaders/SkShader.cpp

@@ -15,6 +15,7 @@
 #include "src/core/SkRasterPipeline.h"
 #include "src/core/SkReadBuffer.h"
 #include "src/core/SkTLazy.h"
+#include "src/core/SkVM.h"
 #include "src/core/SkWriteBuffer.h"
 #include "src/shaders/SkBitmapProcShader.h"
 #include "src/shaders/SkColorShader.h"
@@ -224,6 +225,15 @@ bool SkShaderBase::program(skvm::Builder* p,
     return false;
 }
 
+bool SkShaderBase::onProgram(skvm::Builder*,
+                             const SkMatrix& ctm, const SkMatrix* localM,
+                             SkFilterQuality quality, SkColorSpace* dstCS,
+                             skvm::Uniforms* uniforms, SkArenaAlloc* alloc,
+                             skvm::F32 x, skvm::F32 y,
+                             skvm::F32* r, skvm::F32* g, skvm::F32* b, skvm::F32* a) const {
+    return false;
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 sk_sp<SkFlattenable> SkEmptyShader::CreateProc(SkReadBuffer&) {

src/shaders/SkShaderBase.h

@@ -15,7 +15,7 @@
 #include "src/core/SkEffectPriv.h"
 #include "src/core/SkMask.h"
 #include "src/core/SkTLazy.h"
-#include "src/core/SkVM.h"
+#include "src/core/SkVM_fwd.h"
 
 #if SK_SUPPORT_GPU
 #include "src/gpu/GrFPArgs.h"
@@ -214,15 +214,6 @@ public:
                  skvm::F32 x, skvm::F32 y,
                  skvm::F32* r, skvm::F32* g, skvm::F32* b, skvm::F32* a) const;
 
-    virtual bool onProgram(skvm::Builder*,
-                           const SkMatrix& ctm, const SkMatrix* localM,
-                           SkFilterQuality quality, SkColorSpace* dstCS,
-                           skvm::Uniforms* uniforms, SkArenaAlloc* alloc,
-                           skvm::F32 x, skvm::F32 y,
-                           skvm::F32* r, skvm::F32* g, skvm::F32* b, skvm::F32* a) const {
-        return false;
-    }
-
 protected:
     SkShaderBase(const SkMatrix* localMatrix = nullptr);
 
@@ -251,6 +242,13 @@ private:
     // This is essentially const, but not officially so it can be modified in constructors.
     SkMatrix fLocalMatrix;
 
+    virtual bool onProgram(skvm::Builder*,
+                           const SkMatrix& ctm, const SkMatrix* localM,
+                           SkFilterQuality quality, SkColorSpace* dstCS,
+                           skvm::Uniforms* uniforms, SkArenaAlloc* alloc,
+                           skvm::F32 x, skvm::F32 y,
+                           skvm::F32* r, skvm::F32* g, skvm::F32* b, skvm::F32* a) const;
+
     typedef SkShader INHERITED;
 };