Expose ViewID_OVR impostor in the fragment shader

include/GLSLANG/ShaderLang.h

@@ -223,10 +223,12 @@ const ShCompileOptions SH_TRANSLATE_VIEWID_OVR_TO_UNIFORM = UINT64_C(1) << 31;
 const ShCompileOptions SH_INITIALIZE_UNINITIALIZED_LOCALS = UINT64_C(1) << 32;
 
 // The flag modifies the shader in the following way:
-// Every occurrence of gl_InstanceID and gl_ViewID_OVR is replaced correspondingly by the global
-// temporary variables InstanceID and ViewID_OVR. The following initializers are added at the
-// beginning of main(): ViewID_OVR = uint(gl_InstanceID) % num_views; InstanceID = gl_InstanceID /
-// num_views;
+// Every occurrence of gl_InstanceID is replaced by the global temporary variable InstanceID.
+// Every occurrence of gl_ViewID_OVR is replaced by the varying variable ViewID_OVR.
+// At the beginning of the body of main() in a vertex shader the following initializers are added:
+// ViewID_OVR = uint(gl_InstanceID) % num_views;
+// InstanceID = gl_InstanceID / num_views;
+// ViewID_OVR is added as a varying variable to both the vertex and fragment shaders.
 const ShCompileOptions SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW = UINT64_C(1) << 33;
 
 // Defines alternate strategies for implementing array index clamping.

src/compiler/translator/Compiler.cpp

@@ -429,9 +429,9 @@ TIntermBlock *TCompiler::compileTreeImpl(const char *const shaderStrings[],
             arrayBoundsClamper.MarkIndirectArrayBoundsForClamping(root);
 
         if (success && (compileOptions & SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW) &&
-            parseContext.isMultiviewExtensionEnabled() && getShaderType() == GL_VERTEX_SHADER)
+            parseContext.isMultiviewExtensionEnabled() && getShaderType() != GL_COMPUTE_SHADER)
         {
-            DeclareAndInitBuiltinsForInstancedMultiview(root, getNumViews());
+            DeclareAndInitBuiltinsForInstancedMultiview(root, getNumViews(), getShaderType());
         }
 
         // This pass might emit short circuits so keep it before the short circuit unfolding

src/compiler/translator/DeclareAndInitBuiltinsForInstancedMultiview.cpp

@@ -20,28 +20,26 @@ namespace sh
 namespace
 {
 
-class RenameVariableAndMarkAsInternalTraverser : public TIntermTraverser
+class ReplaceVariableTraverser : public TIntermTraverser
 {
   public:
-    RenameVariableAndMarkAsInternalTraverser(const TString &oldName, const TString &newName)
-        : TIntermTraverser(true, false, false), mOldName(oldName), mNewName(newName)
+    ReplaceVariableTraverser(const TString &symbolName, TIntermSymbol *newSymbol)
+        : TIntermTraverser(true, false, false), mSymbolName(symbolName), mNewSymbol(newSymbol)
     {
     }
 
     void visitSymbol(TIntermSymbol *node) override
     {
         TName &name = node->getName();
-        if (name.getString() == mOldName)
+        if (name.getString() == mSymbolName)
         {
-            node->getTypePointer()->setQualifier(EvqTemporary);
-            name.setInternal(true);
-            name.setString(mNewName);
+            queueReplacement(node, mNewSymbol->deepCopy(), OriginalNode::IS_DROPPED);
         }
     }
 
   private:
-    TString mOldName;
-    TString mNewName;
+    TString mSymbolName;
+    TIntermSymbol *mNewSymbol;
 };
 
 TIntermSymbol *CreateGLInstanceIDSymbol()
@@ -49,15 +47,14 @@ TIntermSymbol *CreateGLInstanceIDSymbol()
     return new TIntermSymbol(0, "gl_InstanceID", TType(EbtInt, EbpHigh, EvqInstanceID));
 }
 
-// Adds initializers for InstanceID and ViewID_OVR at the beginning of main().
-void InitializeBuiltinsInMain(TIntermBlock *root,
-                              TIntermSymbol *instanceIDSymbol,
-                              TIntermSymbol *viewIDSymbol,
-                              unsigned numberOfViews)
+void InitializeViewIDAndInstanceID(TIntermBlock *root,
+                                   TIntermTyped *viewIDSymbol,
+                                   TIntermTyped *instanceIDSymbol,
+                                   unsigned numberOfViews)
 {
     // Create a signed numberOfViews node.
     TConstantUnion *numberOfViewsConstant = new TConstantUnion();
-    numberOfViewsConstant->setIConst(numberOfViews);
+    numberOfViewsConstant->setIConst(static_cast<int>(numberOfViews));
     TIntermConstantUnion *numberOfViewsIntSymbol =
         new TIntermConstantUnion(numberOfViewsConstant, TType(EbtInt, EbpHigh, EvqConst));
 
@@ -67,15 +64,15 @@ void InitializeBuiltinsInMain(TIntermBlock *root,
 
     // Create a InstanceID = gl_InstanceID / numberOfViews node.
     TIntermBinary *instanceIDInitializer =
-        new TIntermBinary(EOpAssign, instanceIDSymbol, normalizedInstanceID);
+        new TIntermBinary(EOpAssign, instanceIDSymbol->deepCopy(), normalizedInstanceID);
 
     // Create a uint(gl_InstanceID) node.
-    TIntermSequence *instanceIDSymbolCastArguments = new TIntermSequence();
-    instanceIDSymbolCastArguments->push_back(CreateGLInstanceIDSymbol());
-    TIntermAggregate *instanceIDAsUint = TIntermAggregate::CreateConstructor(
-        TType(EbtUInt, EbpHigh, EvqTemporary), instanceIDSymbolCastArguments);
+    TIntermSequence *glInstanceIDSymbolCastArguments = new TIntermSequence();
+    glInstanceIDSymbolCastArguments->push_back(CreateGLInstanceIDSymbol());
+    TIntermAggregate *glInstanceIDAsUint = TIntermAggregate::CreateConstructor(
+        TType(EbtUInt, EbpHigh, EvqTemporary), glInstanceIDSymbolCastArguments);
 
-    // Create a unsigned numberOfViews node.
+    // Create an unsigned numberOfViews node.
     TConstantUnion *numberOfViewsUnsignedConstant = new TConstantUnion();
     numberOfViewsUnsignedConstant->setUConst(numberOfViews);
     TIntermConstantUnion *numberOfViewsUintSymbol =
@@ -83,79 +80,60 @@ void InitializeBuiltinsInMain(TIntermBlock *root,
 
     // Create a uint(gl_InstanceID) % numberOfViews node.
     TIntermBinary *normalizedViewID =
-        new TIntermBinary(EOpIMod, instanceIDAsUint, numberOfViewsUintSymbol);
+        new TIntermBinary(EOpIMod, glInstanceIDAsUint, numberOfViewsUintSymbol);
 
     // Create a ViewID_OVR = uint(gl_InstanceID) % numberOfViews node.
-    TIntermBinary *viewIDInitializer = new TIntermBinary(EOpAssign, viewIDSymbol, normalizedViewID);
-
-    // Add nodes to sequence and insert into main.
-    TIntermSequence *initializers = new TIntermSequence();
-    initializers->push_back(viewIDInitializer);
-    initializers->push_back(instanceIDInitializer);
-
-    // Insert init code as a block at the beginning of the main() function.
-    TIntermBlock *initGlobalsBlock = new TIntermBlock();
-    initGlobalsBlock->getSequence()->swap(*initializers);
-
-    TIntermFunctionDefinition *main = FindMain(root);
-    ASSERT(main != nullptr);
-    TIntermBlock *mainBody = main->getBody();
-    ASSERT(mainBody != nullptr);
-    mainBody->getSequence()->insert(mainBody->getSequence()->begin(), initGlobalsBlock);
-}
-
-// Adds declarations for ViewID_OVR and InstanceID in global scope at the beginning of
-// the shader.
-void DeclareBuiltinsInGlobalScope(TIntermBlock *root,
-                                  TIntermSymbol *instanceIDSymbol,
-                                  TIntermSymbol *viewIDSymbol)
-{
-    TIntermSequence *globalSequence = root->getSequence();
-
-    TIntermDeclaration *instanceIDDeclaration = new TIntermDeclaration();
-    instanceIDDeclaration->appendDeclarator(instanceIDSymbol);
+    TIntermBinary *viewIDInitializer =
+        new TIntermBinary(EOpAssign, viewIDSymbol->deepCopy(), normalizedViewID);
 
-    TIntermDeclaration *viewIDOVRDeclaration = new TIntermDeclaration();
-    viewIDOVRDeclaration->appendDeclarator(viewIDSymbol);
-
-    globalSequence->insert(globalSequence->begin(), viewIDOVRDeclaration);
-    globalSequence->insert(globalSequence->begin(), instanceIDDeclaration);
+    // Add initializers at the beginning of main().
+    TIntermBlock *mainBody = FindMainBody(root);
+    mainBody->getSequence()->insert(mainBody->getSequence()->begin(), instanceIDInitializer);
+    mainBody->getSequence()->insert(mainBody->getSequence()->begin(), viewIDInitializer);
 }
 
-// Replaces every occurrence of gl_InstanceID with InstanceID, sets the name to internal
-// and changes the qualifier from EvqInstanceID to EvqTemporary.
-void RenameGLInstanceIDAndMarkAsInternal(TIntermBlock *root)
+// Replaces every occurrence of a symbol with the name specified in symbolName with newSymbolNode.
+void ReplaceSymbol(TIntermBlock *root, const TString &symbolName, TIntermSymbol *newSymbolNode)
 {
-    RenameVariableAndMarkAsInternalTraverser traverser("gl_InstanceID", "InstanceID");
+    ReplaceVariableTraverser traverser(symbolName, newSymbolNode);
     root->traverse(&traverser);
+    traverser.updateTree();
 }
 
-// Replaces every occurrence of gl_ViewID_OVR with ViewID_OVR, sets the name to internal
-// and changes the qualifier from EvqViewIDOVR to EvqTemporary.
-void RenameGLViewIDAndMarkAsInternal(TIntermBlock *root)
+void DeclareGlobalVariable(TIntermBlock *root, TIntermTyped *typedNode)
 {
-    RenameVariableAndMarkAsInternalTraverser traverser("gl_ViewID_OVR", "ViewID_OVR");
-    root->traverse(&traverser);
+    TIntermSequence *globalSequence = root->getSequence();
+    TIntermDeclaration *declaration = new TIntermDeclaration();
+    declaration->appendDeclarator(typedNode->deepCopy());
+    globalSequence->insert(globalSequence->begin(), declaration);
 }
 
 }  // namespace
 
-void DeclareAndInitBuiltinsForInstancedMultiview(TIntermBlock *root, unsigned numberOfViews)
+void DeclareAndInitBuiltinsForInstancedMultiview(TIntermBlock *root,
+                                                 unsigned numberOfViews,
+                                                 GLenum shaderType)
 {
-    TIntermSymbol *instanceIDSymbol = new TIntermSymbol(TSymbolTable::nextUniqueId(), "InstanceID",
-                                                        TType(EbtInt, EbpHigh, EvqGlobal));
-    instanceIDSymbol->setInternal(true);
+    ASSERT(shaderType == GL_VERTEX_SHADER || shaderType == GL_FRAGMENT_SHADER);
 
+    TQualifier viewIDQualifier  = (shaderType == GL_VERTEX_SHADER) ? EvqFlatOut : EvqFlatIn;
     TIntermSymbol *viewIDSymbol = new TIntermSymbol(TSymbolTable::nextUniqueId(), "ViewID_OVR",
-                                                    TType(EbtUInt, EbpHigh, EvqGlobal));
+                                                    TType(EbtUInt, EbpHigh, viewIDQualifier));
     viewIDSymbol->setInternal(true);
 
-    // Renaming the variables should happen before adding the initializers.
-    RenameGLInstanceIDAndMarkAsInternal(root);
-    DeclareBuiltinsInGlobalScope(root, instanceIDSymbol, viewIDSymbol);
-    InitializeBuiltinsInMain(root, instanceIDSymbol->deepCopy()->getAsSymbolNode(),
-                             viewIDSymbol->deepCopy()->getAsSymbolNode(), numberOfViews);
-    RenameGLViewIDAndMarkAsInternal(root);
+    DeclareGlobalVariable(root, viewIDSymbol);
+    ReplaceSymbol(root, "gl_ViewID_OVR", viewIDSymbol);
+    if (shaderType == GL_VERTEX_SHADER)
+    {
+        // Replacing gl_InstanceID with InstanceID should happen before adding the initializers of
+        // InstanceID and ViewID.
+        TIntermSymbol *instanceIDSymbol = new TIntermSymbol(
+            TSymbolTable::nextUniqueId(), "InstanceID", TType(EbtInt, EbpHigh, EvqGlobal));
+        instanceIDSymbol->setInternal(true);
+        DeclareGlobalVariable(root, instanceIDSymbol);
+        ReplaceSymbol(root, "gl_InstanceID", instanceIDSymbol);
+        InitializeViewIDAndInstanceID(root, viewIDSymbol, instanceIDSymbol, numberOfViews);
+    }
 }
 
 }  // namespace sh
\ No newline at end of file

src/compiler/translator/DeclareAndInitBuiltinsForInstancedMultiview.h

@@ -3,24 +3,30 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
-// This pass applies the following modifications to the AST:
-// 1) Replaces every occurrence of gl_InstanceID with InstanceID and marks InstanceID as internal.
-// 2) Adds declarations of the global variables ViewID_OVR and InstanceID.
-// 3) Initializes ViewID_OVR and InstanceID depending on the number of views.
-// 4) Replaces every occurrence of gl_ViewID_OVR with ViewID_OVR and marks ViewID_OVR as internal.
-// The pass should be executed before any variables get collected so that usage of gl_InstanceID is
-// recorded.
+// Regardless of the shader type, the following AST transformations are applied:
+// - Add declaration of View_ID_OVR.
+// - Replace every occurrence of gl_ViewID_OVR with ViewID_OVR, mark ViewID_OVR as internal and
+// declare it as a flat varying.
+// If the shader type is a vertex shader, the following AST transformations are applied:
+// - Replace every occurrence of gl_InstanceID with InstanceID, mark InstanceID as internal and set
+// its qualifier to EvqTemporary.
+// - Add initializers of ViewID_OVR and InstanceID to the beginning of the body of main. The pass
+// should be executed before any variables get collected so that usage of gl_InstanceID is recorded.
 //
 
 #ifndef COMPILER_TRANSLATOR_DECLAREANDINITBUILTINSFORINSTANCEDMULTIVIEW_H_
 #define COMPILER_TRANSLATOR_DECLAREANDINITBUILTINSFORINSTANCEDMULTIVIEW_H_
 
+#include "angle_gl.h"
+
 class TIntermBlock;
 
 namespace sh
 {
 
-void DeclareAndInitBuiltinsForInstancedMultiview(TIntermBlock *root, unsigned numberOfViews);
+void DeclareAndInitBuiltinsForInstancedMultiview(TIntermBlock *root,
+                                                 unsigned numberOfViews,
+                                                 GLenum shaderType);
 
 }  // namespace sh
 

src/compiler/translator/FindMain.cpp

@@ -26,4 +26,13 @@ TIntermFunctionDefinition *FindMain(TIntermBlock *root)
     return nullptr;
 }
 
+TIntermBlock *FindMainBody(TIntermBlock *root)
+{
+    TIntermFunctionDefinition *main = FindMain(root);
+    ASSERT(main != nullptr);
+    TIntermBlock *mainBody = main->getBody();
+    ASSERT(mainBody != nullptr);
+    return mainBody;
+}
+
 }  // namespace sh

src/compiler/translator/FindMain.h

@@ -4,7 +4,7 @@
 // found in the LICENSE file.
 //
 
-// FindMain.h: Find the main() function definition in a given AST.
+// FindMain.h: Adds functions to get the main function definition and its body.
 
 #ifndef COMPILER_TRANSLATOR_FINDMAIN_H_
 #define COMPILER_TRANSLATOR_FINDMAIN_H_
@@ -16,6 +16,7 @@ class TIntermBlock;
 class TIntermFunctionDefinition;
 
 TIntermFunctionDefinition *FindMain(TIntermBlock *root);
+TIntermBlock *FindMainBody(TIntermBlock *root);
 
 }  // namespace sh
 

src/tests/compiler_tests/WEBGL_multiview_test.cpp

@@ -14,6 +14,9 @@
 
 using namespace sh;
 
+namespace
+{
+
 class SymbolOccurrenceCounter : public TIntermTraverser
 {
   public:
@@ -66,6 +69,25 @@ class SymbolOccurrenceCounterByName : public SymbolOccurrenceCounter
     TString mSymbolName;
 };
 
+class SymbolOccurrenceCounterByNameAndQualifier : public SymbolOccurrenceCounter
+{
+  public:
+    SymbolOccurrenceCounterByNameAndQualifier(const TString &symbolName, TQualifier qualifier)
+        : mSymbolName(symbolName), mSymbolQualifier(qualifier)
+    {
+    }
+
+    bool shouldCountSymbol(const TIntermSymbol *node) const override
+    {
+        return node->getName().getString() == mSymbolName &&
+               node->getQualifier() == mSymbolQualifier;
+    }
+
+  private:
+    TString mSymbolName;
+    TQualifier mSymbolQualifier;
+};
+
 class WEBGLMultiviewVertexShaderTest : public ShaderCompileTreeTest
 {
   public:
@@ -122,6 +144,24 @@ class WEBGLMultiviewVertexShaderOutputCodeTest : public MatchOutputCodeTest
     }
 };
 
+void VariableOccursNTimes(TIntermBlock *root,
+                          const TString &varName,
+                          const TQualifier varQualifier,
+                          unsigned n)
+{
+    // Check that there are n occurrences of the variable with the given name and qualifier.
+    SymbolOccurrenceCounterByNameAndQualifier viewIDByNameAndQualifier(varName, varQualifier);
+    root->traverse(&viewIDByNameAndQualifier);
+    EXPECT_EQ(n, viewIDByNameAndQualifier.getNumberOfOccurrences());
+
+    // Check that there are n occurrences of the variable with the given name. By this we guarantee
+    // that there are no other occurrences of the variable with the same name but different
+    // qualifier.
+    SymbolOccurrenceCounterByName viewIDByName(varName);
+    root->traverse(&viewIDByName);
+    EXPECT_EQ(n, viewIDByName.getNumberOfOccurrences());
+}
+
 // Invalid combination of extensions (restricted in the WEBGL_multiview spec).
 TEST_F(WEBGLMultiviewVertexShaderTest, InvalidBothMultiviewAndMultiview2)
 {
@@ -663,9 +703,9 @@ TEST_F(WEBGLMultiviewVertexShaderTest, GLViewIDIsRenamed)
     mASTRoot->traverse(&glViewIDOVRByQualifier);
     EXPECT_EQ(0u, glViewIDOVRByQualifier.getNumberOfOccurrences());
 
-    SymbolOccurrenceCounterByName viewIDByName("ViewID_OVR");
-    mASTRoot->traverse(&viewIDByName);
-    EXPECT_EQ(6u, viewIDByName.getNumberOfOccurrences());
+    SymbolOccurrenceCounterByNameAndQualifier viewIDByNameAndQualifier("ViewID_OVR", EvqFlatOut);
+    mASTRoot->traverse(&viewIDByNameAndQualifier);
+    EXPECT_EQ(6u, viewIDByNameAndQualifier.getNumberOfOccurrences());
 }
 
 // The test checks that ViewID_OVR and InstanceID have the correct initializers based on the
@@ -741,4 +781,33 @@ TEST_F(WEBGLMultiviewVertexShaderTest, InstaceIDCollectedESSL1)
         isGLInstanceIDFound = (attributes[i].name == "gl_InstanceID");
     }
     EXPECT_TRUE(isGLInstanceIDFound);
-}
+}
\ No newline at end of file
+
+// Test that ViewID_OVR is declared as a flat input variable in an ESSL 3.00 fragment shader.
+TEST_F(WEBGLMultiviewFragmentShaderTest, ViewIDDeclaredAsFlatInput)
+{
+    const std::string &shaderString =
+        "#version 300 es\n"
+        "#extension GL_OVR_multiview2 : require\n"
+        "void main()\n"
+        "{\n"
+        "}\n";
+    mExtraCompileOptions |= SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW;
+    compileAssumeSuccess(shaderString);
+    VariableOccursNTimes(mASTRoot, "ViewID_OVR", EvqFlatIn, 1u);
+}
+
+// Test that ViewID_OVR is declared as a flat output variable in an ESSL 1.00 vertex shader.
+TEST_F(WEBGLMultiviewVertexShaderTest, ViewIDDeclaredAsFlatOutput)
+{
+    const std::string &shaderString =
+        "#extension GL_OVR_multiview2 : require\n"
+        "void main()\n"
+        "{\n"
+        "}\n";
+    mExtraCompileOptions |= SH_INITIALIZE_BUILTINS_FOR_INSTANCED_MULTIVIEW;
+    compileAssumeSuccess(shaderString);
+    VariableOccursNTimes(mASTRoot, "ViewID_OVR", EvqFlatOut, 2u);
+}
+
+}  // namespace