Add an option to initialize varyings without static use in vertex shaders

include/GLSLANG/ShaderLang.h

@@ -212,8 +212,8 @@ typedef enum {
   // This flag limits the depth of the call stack.
   SH_LIMIT_CALL_STACK_DEPTH = 0x4000,
 
-  // This flag initializes gl_Position to vec4(0.0, 0.0, 0.0, 1.0) at
-  // the beginning of the vertex shader, and has no effect in the
+  // This flag initializes gl_Position to vec4(0,0,0,0) at the
+  // beginning of the vertex shader's main(), and has no effect in the
   // fragment shader. It is intended as a workaround for drivers which
   // incorrectly fail to link programs if gl_Position is not written.
   SH_INIT_GL_POSITION = 0x8000,
@@ -224,6 +224,12 @@ typedef enum {
   // This is to work around a MacOSX driver bug that |b| is executed
   // independent of |a|'s value.
   SH_UNFOLD_SHORT_CIRCUIT = 0x10000,
+
+  // This flag initializes varyings without static use in vertex shader
+  // at the beginning of main(), and has no effects in the fragment shader.
+  // It is intended as a workaround for drivers which incorrectly optimize
+  // out such varyings and cause a link failure.
+  SH_INIT_VARYINGS_WITHOUT_STATIC_USE = 0x20000,
 } ShCompileOptions;
 
 // Defines alternate strategies for implementing array index clamping.

src/compiler/translator/InitializeGLPosition.cpp

-//
-// Copyright (c) 2002-2013 The ANGLE Project Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-//
-
-#include "compiler/translator/InitializeGLPosition.h"
-#include "compiler/translator/compilerdebug.h"
-
-bool InitializeGLPosition::visitAggregate(Visit visit, TIntermAggregate* node)
-{
-    bool visitChildren = !mCodeInserted;
-    switch (node->getOp())
-    {
-      case EOpSequence: break;
-      case EOpFunction:
-      {
-        // Function definition.
-        ASSERT(visit == PreVisit);
-        if (node->getName() == "main(")
-        {
-            TIntermSequence &sequence = node->getSequence();
-            ASSERT((sequence.size() == 1) || (sequence.size() == 2));
-            TIntermAggregate *body = NULL;
-            if (sequence.size() == 1)
-            {
-                body = new TIntermAggregate(EOpSequence);
-                sequence.push_back(body);
-            }
-            else
-            {
-                body = sequence[1]->getAsAggregate();
-            }
-            ASSERT(body);
-            insertCode(body->getSequence());
-            mCodeInserted = true;
-        }
-        break;
-      }
-      default: visitChildren = false; break;
-    }
-    return visitChildren;
-}
-
-void InitializeGLPosition::insertCode(TIntermSequence& sequence)
-{
-    TIntermBinary *binary = new TIntermBinary(EOpAssign);
-    sequence.insert(sequence.begin(), binary);
-
-    TIntermSymbol *left = new TIntermSymbol(
-        0, "gl_Position", TType(EbtFloat, EbpUndefined, EvqPosition, 4));
-    binary->setLeft(left);
-
-    ConstantUnion *u = new ConstantUnion[4];
-    for (int ii = 0; ii < 3; ++ii)
-        u[ii].setFConst(0.0f);
-    u[3].setFConst(1.0f);
-    TIntermConstantUnion *right = new TIntermConstantUnion(
-        u, TType(EbtFloat, EbpUndefined, EvqConst, 4));
-    binary->setRight(right);
-}

src/compiler/translator/InitializeVariables.cpp

+//
+// Copyright (c) 2002-2013 The ANGLE Project Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+
+#include "compiler/translator/InitializeVariables.h"
+#include "compiler/translator/compilerdebug.h"
+
+namespace
+{
+
+TIntermConstantUnion* constructFloatConstUnionNode(const TType& type)
+{
+    TType myType = type;
+    unsigned char size = myType.getNominalSize();
+    if (myType.isMatrix())
+        size *= size;
+    ConstantUnion *u = new ConstantUnion[size];
+    for (int ii = 0; ii < size; ++ii)
+        u[ii].setFConst(0.0f);
+
+    myType.clearArrayness();
+    myType.setQualifier(EvqConst);
+    TIntermConstantUnion *node = new TIntermConstantUnion(u, myType);
+    return node;
+}
+
+TIntermConstantUnion* constructIndexNode(int index)
+{
+    ConstantUnion *u = new ConstantUnion[1];
+    u[0].setIConst(index);
+
+    TType type(EbtInt, EbpUndefined, EvqConst, 1);
+    TIntermConstantUnion *node = new TIntermConstantUnion(u, type);
+    return node;
+}
+
+}  // namespace anonymous
+
+bool InitializeVariables::visitAggregate(Visit visit, TIntermAggregate* node)
+{
+    bool visitChildren = !mCodeInserted;
+    switch (node->getOp())
+    {
+      case EOpSequence:
+        break;
+      case EOpFunction:
+      {
+        // Function definition.
+        ASSERT(visit == PreVisit);
+        if (node->getName() == "main(")
+        {
+            TIntermSequence &sequence = node->getSequence();
+            ASSERT((sequence.size() == 1) || (sequence.size() == 2));
+            TIntermAggregate *body = NULL;
+            if (sequence.size() == 1)
+            {
+                body = new TIntermAggregate(EOpSequence);
+                sequence.push_back(body);
+            }
+            else
+            {
+                body = sequence[1]->getAsAggregate();
+            }
+            ASSERT(body);
+            insertInitCode(body->getSequence());
+            mCodeInserted = true;
+        }
+        break;
+      }
+      default:
+        visitChildren = false;
+        break;
+    }
+    return visitChildren;
+}
+
+void InitializeVariables::insertInitCode(TIntermSequence& sequence)
+{
+    for (size_t ii = 0; ii < mVariables.size(); ++ii)
+    {
+        const InitVariableInfo& varInfo = mVariables[ii];
+
+        if (varInfo.type.isArray())
+        {
+            for (int index = varInfo.type.getArraySize() - 1; index >= 0; --index)
+            {
+                TIntermBinary *assign = new TIntermBinary(EOpAssign);
+                sequence.insert(sequence.begin(), assign);
+
+                TIntermBinary *indexDirect = new TIntermBinary(EOpIndexDirect);
+                TIntermSymbol *symbol = new TIntermSymbol(0, varInfo.name, varInfo.type);
+                indexDirect->setLeft(symbol);
+                TIntermConstantUnion *indexNode = constructIndexNode(index);
+                indexDirect->setRight(indexNode);
+
+                assign->setLeft(indexDirect);
+
+                TIntermConstantUnion *zeroConst = constructFloatConstUnionNode(varInfo.type);
+                assign->setRight(zeroConst);
+            }
+        }
+        else
+        {
+            TIntermBinary *assign = new TIntermBinary(EOpAssign);
+            sequence.insert(sequence.begin(), assign);
+            TIntermSymbol *symbol = new TIntermSymbol(0, varInfo.name, varInfo.type);
+            assign->setLeft(symbol);
+            TIntermConstantUnion *zeroConst = constructFloatConstUnionNode(varInfo.type);
+            assign->setRight(zeroConst);
+        }
+
+    }
+}
+

src/compiler/translator/InitializeGLPosition.h → src/compiler/translator/InitializeVariables.h

@@ -4,17 +4,34 @@
 // found in the LICENSE file.
 //
 
-#ifndef COMPILER_INITIALIZE_GL_POSITION_H_
-#define COMPILER_INITIALIZE_GL_POSITION_H_
+#ifndef COMPILER_INITIALIZE_VARIABLES_H_
+#define COMPILER_INITIALIZE_VARIABLES_H_
 
 #include "compiler/translator/intermediate.h"
 
-class InitializeGLPosition : public TIntermTraverser
+class InitializeVariables : public TIntermTraverser
 {
-public:
-    InitializeGLPosition() : mCodeInserted(false) { }
-
-protected:
+  public:
+    struct InitVariableInfo
+    {
+        TString name;
+        TType type;
+
+        InitVariableInfo(const TString& _name, const TType& _type)
+            : name(_name),
+              type(_type)
+        {
+        }
+    };
+    typedef TVector<InitVariableInfo> InitVariableInfoList;
+
+    InitializeVariables(const InitVariableInfoList& vars)
+        : mCodeInserted(false),
+          mVariables(vars)
+    {
+    }
+
+  protected:
     virtual bool visitBinary(Visit visit, TIntermBinary* node) { return false; }
     virtual bool visitUnary(Visit visit, TIntermUnary* node) { return false; }
     virtual bool visitSelection(Visit visit, TIntermSelection* node) { return false; }
@@ -23,11 +40,11 @@ protected:
 
     virtual bool visitAggregate(Visit visit, TIntermAggregate* node);
 
-private:
-    // Insert AST node in the beginning of main() for "gl_Position = vec4(0.0, 0.0, 0.0, 1.0);".
-    void insertCode(TIntermSequence& sequence);
+  private:
+    void insertInitCode(TIntermSequence& sequence);
 
+    InitVariableInfoList mVariables;
     bool mCodeInserted;
 };
 
-#endif  // COMPILER_INITIALIZE_GL_POSITION_H_
+#endif  // COMPILER_INITIALIZE_VARIABLES_H_

src/compiler/translator/ShHandle.h

@@ -103,6 +103,16 @@ protected:
     // Returns true if, after applying the packing rules in the GLSL 1.017 spec
     // Appendix A, section 7, the shader does not use too many uniforms.
     bool enforcePackingRestrictions();
+    // Insert statements to initialize varyings without static use in the beginning
+    // of main(). It is to work around a Mac driver where such varyings in a vertex
+    // shader may be optimized out incorrectly at compile time, causing a link failure.
+    // This function should only be applied to vertex shaders.
+    void initializeVaryingsWithoutStaticUse(TIntermNode* root);
+    // Insert gl_Position = vec4(0,0,0,0) to the beginning of main().
+    // It is to work around a Linux driver bug where missing this causes compile failure
+    // while spec says it is allowed.
+    // This function should only be applied to vertex shaders.
+    void initializeGLPosition(TIntermNode* root);
     // Returns true if the shader passes the restrictions that aim to prevent timing attacks.
     bool enforceTimingRestrictions(TIntermNode* root, bool outputGraph);
     // Returns true if the shader does not use samplers.

src/compiler/translator/VariableInfo.cpp

@@ -163,10 +163,12 @@ void getBuiltInVariableInfo(const TType& type,
         varInfo.name = (name + "[0]").c_str();
         varInfo.mappedName = (mappedName + "[0]").c_str();
         varInfo.size = type.getArraySize();
+        varInfo.isArray = true;
     } else {
         varInfo.name = name.c_str();
         varInfo.mappedName = mappedName.c_str();
         varInfo.size = 1;
+        varInfo.isArray = false;
     }
     varInfo.precision = type.getPrecision();
     varInfo.type = getVariableDataType(type);
@@ -214,6 +216,7 @@ TVariableInfo* findVariable(const TType& type,
 TVariableInfo::TVariableInfo()
     : type(SH_NONE),
       size(0),
+      isArray(false),
       precision(EbpUndefined),
       staticUse(false)
 {
@@ -222,6 +225,7 @@ TVariableInfo::TVariableInfo()
 TVariableInfo::TVariableInfo(ShDataType type, int size)
     : type(type),
       size(size),
+      isArray(false),
       precision(EbpUndefined),
       staticUse(false)
 {

src/compiler/translator/VariableInfo.h

@@ -20,6 +20,7 @@ struct TVariableInfo {
     TPersistString mappedName;
     ShDataType type;
     int size;
+    bool isArray;
     TPrecision precision;
     bool staticUse;
 };