Use noperspective interpolation for 2D draws

Adds a mechanism to notify GrGLSLVaryingHandler that a shader will not
emit geometry in perspective. This gives it a chance to use the
noperspective keyword if it is supported.

Updates the existing processors to notify the varying handler when
there is no perspective.

Begins using the noperspective keyword in GrGLGpu internal shaders.

Web scenes with observable benefit (Pixel C, gpu config):

  tabl_nofolo.skp        4.62 -> 3.33 ms   28%
  desk_tigersvg.skp      26.5 -> 24 ms      9%
  desk_pokemonwiki.skp   16.1 -> 14.9 ms    7%
  tabl_deviantart.skp    3.97 -> 3.7 ms     7%
  desk_gws.skp           3.85 -> 3.65 ms    5%

Also adds new methods for creating varyings with flat interpolation.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1673093002

Review URL: https://codereview.chromium.org/1673093002

4 files changed, 73 insertions, 30 deletions

diff --git a/src/gpu/gl/GrGLCaps.cpp b/src/gpu/gl/GrGLCaps.cpp
index 79bb22efac..6dc5ee8c4f 100644
--- a/src/gpu/gl/GrGLCaps.cpp
+++ b/src/gpu/gl/GrGLCaps.cpp
@@ -596,6 +596,24 @@ void GrGLCaps::initGLSL(const GrGLContextInfo& ctxInfo) {
 
     glslCaps->fBindlessTextureSupport = ctxInfo.hasExtension("GL_NV_bindless_texture");
 
+    if (kGL_GrGLStandard == standard) {
+        glslCaps->fFlatInterpolationSupport = ctxInfo.glslGeneration() >= k130_GrGLSLGeneration;
+    } else {
+        glslCaps->fFlatInterpolationSupport =
+            ctxInfo.glslGeneration() >= k330_GrGLSLGeneration; // This is the value for GLSL ES 3.0.
+    }
+
+    if (kGL_GrGLStandard == standard) {
+        glslCaps->fNoPerspectiveInterpolationSupport =
+            ctxInfo.glslGeneration() >= k130_GrGLSLGeneration;
+    } else {
+        if (ctxInfo.hasExtension("GL_NV_shader_noperspective_interpolation")) {
+            glslCaps->fNoPerspectiveInterpolationSupport = true;
+            glslCaps->fNoPerspectiveInterpolationExtensionString =
+                "GL_NV_shader_noperspective_interpolation";
+        }
+    }
+
     // Adreno GPUs have a tendency to drop tiles when there is a divide-by-zero in a shader
     glslCaps->fDropsTileOnZeroDivide = kQualcomm_GrGLVendor == ctxInfo.vendor();
 
diff --git a/src/gpu/gl/GrGLGpu.cpp b/src/gpu/gl/GrGLGpu.cpp
index b9a5ee9837..be315dab1e 100644
--- a/src/gpu/gl/GrGLGpu.cpp
+++ b/src/gpu/gl/GrGLGpu.cpp
@@ -285,7 +285,8 @@ GrGLGpu::~GrGLGpu() {
 }
 
 void GrGLGpu::createPLSSetupProgram() {
-    const char* version = this->glCaps().glslCaps()->versionDeclString();
+    const GrGLSLCaps* glslCaps = this->glCaps().glslCaps();
+    const char* version = glslCaps->versionDeclString();
 
     GrGLSLShaderVar aVertex("a_vertex", kVec2f_GrSLType, GrShaderVar::kAttribute_TypeModifier);
     GrGLSLShaderVar uTexCoordXform("u_texCoordXform", kVec4f_GrSLType,
@@ -295,13 +296,19 @@ void GrGLGpu::createPLSSetupProgram() {
     GrGLSLShaderVar vTexCoord("v_texCoord", kVec2f_GrSLType, GrShaderVar::kVaryingOut_TypeModifier);
     
     SkString vshaderTxt(version);
-    aVertex.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+    if (glslCaps->noperspectiveInterpolationSupport()) {
+        if (const char* extension = glslCaps->noperspectiveInterpolationExtensionString()) {
+            vshaderTxt.appendf("#extension %s : require\n", extension);
+        }
+        vTexCoord.addModifier("noperspective");
+    }
+    aVertex.appendDecl(glslCaps, &vshaderTxt);
     vshaderTxt.append(";");
-    uTexCoordXform.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+    uTexCoordXform.appendDecl(glslCaps, &vshaderTxt);
     vshaderTxt.append(";");
-    uPosXform.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+    uPosXform.appendDecl(glslCaps, &vshaderTxt);
     vshaderTxt.append(";");
-    vTexCoord.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+    vTexCoord.appendDecl(glslCaps, &vshaderTxt);
     vshaderTxt.append(";");
     
     vshaderTxt.append(
@@ -313,17 +320,20 @@ void GrGLGpu::createPLSSetupProgram() {
     );
 
     SkString fshaderTxt(version);
+    if (glslCaps->noperspectiveInterpolationSupport()) {
+        if (const char* extension = glslCaps->noperspectiveInterpolationExtensionString()) {
+            fshaderTxt.appendf("#extension %s : require\n", extension);
+        }
+    }
     fshaderTxt.append("#extension ");
-    fshaderTxt.append(this->glCaps().glslCaps()->fbFetchExtensionString());
+    fshaderTxt.append(glslCaps->fbFetchExtensionString());
     fshaderTxt.append(" : require\n");
     fshaderTxt.append("#extension GL_EXT_shader_pixel_local_storage : require\n");
-    GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision,
-                                                 *this->glCaps().glslCaps(),
-                                                 &fshaderTxt);
+    GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision, *glslCaps, &fshaderTxt);
     vTexCoord.setTypeModifier(GrShaderVar::kVaryingIn_TypeModifier);
-    vTexCoord.appendDecl(this->glCaps().glslCaps(), &fshaderTxt);
+    vTexCoord.appendDecl(glslCaps, &fshaderTxt);
     fshaderTxt.append(";");
-    uTexture.appendDecl(this->glCaps().glslCaps(), &fshaderTxt);
+    uTexture.appendDecl(glslCaps, &fshaderTxt);
     fshaderTxt.append(";");
 
     fshaderTxt.appendf(
@@ -3300,7 +3310,8 @@ void GrGLGpu::createCopyPrograms() {
     for (size_t i = 0; i < SK_ARRAY_COUNT(fCopyPrograms); ++i) {
         fCopyPrograms[i].fProgram = 0;
     }
-    const char* version = this->glCaps().glslCaps()->versionDeclString();
+    const GrGLSLCaps* glslCaps = this->glCaps().glslCaps();
+    const char* version = glslCaps->versionDeclString();
     static const GrSLType kSamplerTypes[3] = { kSampler2D_GrSLType, kSamplerExternal_GrSLType,
                                                kSampler2DRect_GrSLType };
     SkASSERT(3 == SK_ARRAY_COUNT(fCopyPrograms));
@@ -3326,13 +3337,20 @@ void GrGLGpu::createCopyPrograms() {
                                    GrShaderVar::kOut_TypeModifier);
 
         SkString vshaderTxt(version);
-        aVertex.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+        if (glslCaps->noperspectiveInterpolationSupport()) {
+            if (const char* extension = glslCaps->noperspectiveInterpolationExtensionString()) {
+                vshaderTxt.appendf("#extension %s : require\n", extension);
+            }
+            vTexCoord.addModifier("noperspective");
+        }
+
+        aVertex.appendDecl(glslCaps, &vshaderTxt);
         vshaderTxt.append(";");
-        uTexCoordXform.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+        uTexCoordXform.appendDecl(glslCaps, &vshaderTxt);
         vshaderTxt.append(";");
-        uPosXform.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+        uPosXform.appendDecl(glslCaps, &vshaderTxt);
         vshaderTxt.append(";");
-        vTexCoord.appendDecl(this->glCaps().glslCaps(), &vshaderTxt);
+        vTexCoord.appendDecl(glslCaps, &vshaderTxt);
         vshaderTxt.append(";");
 
         vshaderTxt.append(
@@ -3345,21 +3363,25 @@ void GrGLGpu::createCopyPrograms() {
         );
 
         SkString fshaderTxt(version);
+        if (glslCaps->noperspectiveInterpolationSupport()) {
+            if (const char* extension = glslCaps->noperspectiveInterpolationExtensionString()) {
+                fshaderTxt.appendf("#extension %s : require\n", extension);
+            }
+        }
         if (kSamplerTypes[i] == kSamplerExternal_GrSLType) {
             fshaderTxt.appendf("#extension %s : require\n",
-                               this->glCaps().glslCaps()->externalTextureExtensionString());
+                               glslCaps->externalTextureExtensionString());
         }
-        GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision,
-                                                     *this->glCaps().glslCaps(),
+        GrGLSLAppendDefaultFloatPrecisionDeclaration(kDefault_GrSLPrecision, *glslCaps,
                                                      &fshaderTxt);
         vTexCoord.setTypeModifier(GrShaderVar::kVaryingIn_TypeModifier);
-        vTexCoord.appendDecl(this->glCaps().glslCaps(), &fshaderTxt);
+        vTexCoord.appendDecl(glslCaps, &fshaderTxt);
         fshaderTxt.append(";");
-        uTexture.appendDecl(this->glCaps().glslCaps(), &fshaderTxt);
+        uTexture.appendDecl(glslCaps, &fshaderTxt);
         fshaderTxt.append(";");
         const char* fsOutName;
-        if (this->glCaps().glslCaps()->mustDeclareFragmentShaderOutput()) {
-            oFragColor.appendDecl(this->glCaps().glslCaps(), &fshaderTxt);
+        if (glslCaps->mustDeclareFragmentShaderOutput()) {
+            oFragColor.appendDecl(glslCaps, &fshaderTxt);
             fshaderTxt.append(";");
             fsOutName = oFragColor.c_str();
         } else {
diff --git a/src/gpu/gl/GrGLVaryingHandler.cpp b/src/gpu/gl/GrGLVaryingHandler.cpp
index b27a9960ec..a2d4e9d1b9 100644
--- a/src/gpu/gl/GrGLVaryingHandler.cpp
+++ b/src/gpu/gl/GrGLVaryingHandler.cpp
@@ -24,8 +24,14 @@ GrGLSLVaryingHandler::VaryingHandle GrGLVaryingHandler::addPathProcessingVarying
              glPB->fArgs.fPrimitiveProcessor->numAttribs() == 0);
 #endif
     this->addVarying(name, v, fsPrecision);
-    VaryingInfo& varyingInfo = fPathProcVaryingInfos.push_back();
-    varyingInfo.fVariable = fFragInputs.back();
+    auto varyingInfo = fPathProcVaryingInfos.push_back();
     varyingInfo.fLocation = fPathProcVaryingInfos.count() - 1;
     return VaryingHandle(varyingInfo.fLocation);
 }
+
+void GrGLVaryingHandler::onFinalize() {
+    SkASSERT(fPathProcVaryingInfos.empty() || fPathProcVaryingInfos.count() == fFragInputs.count());
+    for (int i = 0; i < fPathProcVaryingInfos.count(); ++i) {
+        fPathProcVaryingInfos[i].fVariable = fFragInputs[i];
+    }
+}
diff --git a/src/gpu/gl/GrGLVaryingHandler.h b/src/gpu/gl/GrGLVaryingHandler.h
index fe8c3dca69..c4e5ba457e 100644
--- a/src/gpu/gl/GrGLVaryingHandler.h
+++ b/src/gpu/gl/GrGLVaryingHandler.h
@@ -24,12 +24,9 @@ public:
                                            GrSLPrecision fsPrecision = kDefault_GrSLPrecision);
 
 private:
-    void onFinalize() override {}
+    void onFinalize() override;
 
-    typedef GrGLProgramDataManager::VaryingInfo VaryingInfo;
-    typedef GrGLProgramDataManager::VaryingInfoArray VaryingInfoArray;
-
-    VaryingInfoArray fPathProcVaryingInfos;
+    GrGLProgramDataManager::VaryingInfoArray fPathProcVaryingInfos;
 
     friend class GrGLProgramBuilder;