Fix mismatch issue with precision qualifiers.

src/libANGLE/renderer/glslang_wrapper_utils.cpp

@@ -994,12 +994,17 @@ class SpirvTransformer final : angle::NonCopyable
     bool transformEntryPoint(const uint32_t *instruction, size_t wordCount);
     bool transformDecorate(const uint32_t *instruction, size_t wordCount);
     bool transformTypePointer(const uint32_t *instruction, size_t wordCount);
+    bool transformReturn(const uint32_t *instruction, size_t wordCount);
     bool transformVariable(const uint32_t *instruction, size_t wordCount);
     bool transformExecutionMode(const uint32_t *instruction, size_t wordCount);
 
     // Any other instructions:
+    void writeInputPreamble();
     size_t copyInstruction(const uint32_t *instruction, size_t wordCount);
     uint32_t getNewId();
+    void writeOpLoad(uint32_t id, uint32_t typeId, uint32_t tempVarId);
+    void writeOpStore(uint32_t tempVarId, uint32_t destId);
+    void writeOpVariable(uint32_t id, uint32_t typeId, uint32_t storageClassId);
 
     // SPIR-V to transform:
     const std::vector<uint32_t> &mSpirvBlobIn;
@@ -1019,6 +1024,9 @@ class SpirvTransformer final : angle::NonCopyable
     // Traversal state:
     size_t mCurrentWord           = 0;
     bool mIsInFunctionSection     = false;
+    bool mInsertFunctionVariables = false;
+    uint32_t mEntryPointId        = 0;
+    uint32_t mOpFunctionId        = 0;
 
     // Transformation state:
 
@@ -1035,7 +1043,14 @@ class SpirvTransformer final : angle::NonCopyable
     // duplicated with a similar instruction but which defines a type with the Private storage
     // class.  If inactive varyings are encountered, its type is changed to the Private one.  The
     // following vector maps the Output type id to the corresponding Private one.
-    std::vector<uint32_t> mTypePointerTransformedId;
+    struct TransformedIDs
+    {
+        uint32_t privateID;
+        uint32_t typeID;
+    };
+    std::vector<TransformedIDs> mTypePointerTransformedId;
+    std::vector<uint32_t> mFixedVaryingId;
+    std::vector<uint32_t> mFixedVaryingTypeId;
 };
 
 bool SpirvTransformer::transform()
@@ -1053,13 +1068,14 @@ bool SpirvTransformer::transform()
     // Make sure the SpirvBlob is not reused.
     ASSERT(mSpirvBlobOut->empty());
 
+    // Copy the header to SpirvBlob, we need that to be defined for SpirvTransformer::getNewId to
+    // work.
+    mSpirvBlobOut->assign(mSpirvBlobIn.begin(), mSpirvBlobIn.begin() + kHeaderIndexInstructions);
+
     // First, find all necessary ids and associate them with the information required to transform
     // their decorations.
     resolveVariableIds();
 
-    // Copy the header to SpirvBlob
-    mSpirvBlobOut->assign(mSpirvBlobIn.begin(), mSpirvBlobIn.begin() + kHeaderIndexInstructions);
-
     mCurrentWord = kHeaderIndexInstructions;
     while (mCurrentWord < mSpirvBlobIn.size())
     {
@@ -1113,7 +1129,10 @@ void SpirvTransformer::resolveVariableIds()
 
     // Allocate storage for Output type pointer map.  At index i, this vector holds the identical
     // type as %i except for its storage class turned to Private.
-    mTypePointerTransformedId.resize(indexBound + 1, 0);
+    // Also store a FunctionID and TypeID for when we need to fix a precision mismatch
+    mTypePointerTransformedId.resize(indexBound + 1, {0, 0});
+    mFixedVaryingId.resize(indexBound + 1, {0});
+    mFixedVaryingTypeId.resize(indexBound + 1, {0});
 
     size_t currentWord = kHeaderIndexInstructions;
 
@@ -1155,6 +1174,7 @@ void SpirvTransformer::resolveVariableIds()
 
 void SpirvTransformer::transformInstruction()
 {
+    ASSERT(mCurrentWord < mSpirvBlobIn.size());
     const uint32_t *instruction = &mSpirvBlobIn[mCurrentWord];
 
     const uint32_t wordCount = GetSpirvInstructionLength(instruction);
@@ -1165,9 +1185,16 @@ void SpirvTransformer::transformInstruction()
 
     if (opCode == spv::OpFunction)
     {
+        constexpr size_t kFunctionIdIndex = 2;
+        mOpFunctionId                     = instruction[kFunctionIdIndex];
+
         // SPIR-V is structured in sections.  Function declarations come last.  Only Op*Access*
         // opcodes inside functions need to be inspected.
         mIsInFunctionSection = true;
+
+        // Only write function variables for the EntryPoint function for non-compute shaders
+        mInsertFunctionVariables =
+            mOpFunctionId == mEntryPointId && mShaderType != gl::ShaderType::Compute;
     }
 
     // Only look at interesting instructions.
@@ -1175,6 +1202,18 @@ void SpirvTransformer::transformInstruction()
 
     if (mIsInFunctionSection)
     {
+        // After we process an OpFunction instruction and any instructions that must come
+        // immediately after OpFunction we need to check if there are any precision mismatches that
+        // need to be handled. If so, output OpVariable for each variable that needed to change from
+        // a StorageClassOutput to a StorageClassFunction.
+        if (mInsertFunctionVariables && opCode != spv::OpFunction &&
+            opCode != spv::OpFunctionParameter && opCode != spv::OpLabel &&
+            opCode != spv::OpVariable)
+        {
+            writeInputPreamble();
+            mInsertFunctionVariables = false;
+        }
+
         // Look at in-function opcodes.
         switch (opCode)
         {
@@ -1184,6 +1223,10 @@ void SpirvTransformer::transformInstruction()
             case spv::OpInBoundsPtrAccessChain:
                 transformed = transformAccessChain(instruction, wordCount);
                 break;
+
+            case spv::OpReturn:
+                transformed = transformReturn(instruction, wordCount);
+                break;
             default:
                 break;
         }
@@ -1241,6 +1284,29 @@ void SpirvTransformer::transformInstruction()
     mCurrentWord += wordCount;
 }
 
+// Called by transformInstruction to insert necessary instructions for casting varying
+void SpirvTransformer::writeInputPreamble()
+{
+    for (uint32_t id = 0; id < mVariableInfoById.size(); id++)
+    {
+        const ShaderInterfaceVariableInfo *info = mVariableInfoById[id];
+        if (info && info->useRelaxedPrecision && info->activeStages[mShaderType] &&
+            !info->varyingIsOutput)
+        {
+            // This is an input varying, need to cast the mediump value that came from
+            // the previous stage into a highp value that the code wants to work with.
+
+            // Build OpLoad instruction to load the mediump value into a temporary
+            uint32_t tempVar = getNewId();
+            writeOpLoad(mFixedVaryingId[id], mFixedVaryingTypeId[id], tempVar);
+
+            // Build OpStore instruction to cast the mediump value to highp for use in
+            // the function
+            writeOpStore(tempVar, id);
+        }
+    }
+}
+
 void SpirvTransformer::visitName(const uint32_t *instruction)
 {
     // We currently don't have any big-endian devices in the list of supported platforms.  Literal
@@ -1361,6 +1427,13 @@ void SpirvTransformer::visitVariable(const uint32_t *instruction)
     // Associate the id of this name with its info.
     mVariableInfoById[id] = info;
 
+    if (info && info->useRelaxedPrecision && info->activeStages[mShaderType] &&
+        mFixedVaryingId[id] == 0)
+    {
+        mFixedVaryingId[id]     = getNewId();
+        mFixedVaryingTypeId[id] = typeId;
+    }
+
     // Note if the variable is captured by transform feedback.  In that case, the TransformFeedback
     // capability needs to be added.
     if (mShaderType != gl::ShaderType::Fragment &&
@@ -1380,6 +1453,7 @@ bool SpirvTransformer::transformDecorate(const uint32_t *instruction, size_t wor
     uint32_t id         = instruction[kIdIndex];
     uint32_t decoration = instruction[kDecorationIndex];
 
+    ASSERT(id < mVariableInfoById.size());
     const ShaderInterfaceVariableInfo *info = mVariableInfoById[id];
 
     // If variable is not a shader interface variable that needs modification, there's nothing to
@@ -1408,6 +1482,16 @@ bool SpirvTransformer::transformDecorate(const uint32_t *instruction, size_t wor
         case spv::DecorationDescriptorSet:
             newDecorationValue = info->descriptorSet;
             break;
+        case spv::DecorationFlat:
+            if (info->useRelaxedPrecision)
+            {
+                // Change the id to replacement variable
+                ASSERT(mFixedVaryingId[id] != 0);
+                const size_t instructionOffset = copyInstruction(instruction, wordCount);
+                (*mSpirvBlobOut)[instructionOffset + kIdIndex] = mFixedVaryingId[id];
+                return true;
+            }
+            break;
         default:
             break;
     }
@@ -1429,6 +1513,23 @@ bool SpirvTransformer::transformDecorate(const uint32_t *instruction, size_t wor
         return true;
     }
 
+    if (info->useRelaxedPrecision)
+    {
+        // Change the id of the location decoration to replacement variable
+        ASSERT(mFixedVaryingId[id] != 0);
+        (*mSpirvBlobOut)[instructionOffset + kIdIndex] = mFixedVaryingId[id];
+
+        // The replacement variable is always reduced precision so add that decoration to
+        // fixedVaryingId
+        constexpr size_t kInstDecorateRelaxedPrecisionWordCount = 3;
+        uint32_t inst[kInstDecorateRelaxedPrecisionWordCount];
+        SetSpirvInstructionLength(inst, kInstDecorateRelaxedPrecisionWordCount);
+        SetSpirvInstructionOp(inst, spv::OpDecorate);
+        inst[kIdIndex]         = mFixedVaryingId[id];
+        inst[kDecorationIndex] = spv::DecorationRelaxedPrecision;
+        copyInstruction(inst, kInstDecorateRelaxedPrecisionWordCount);
+    }
+
     // Add component decoration, if any.
     if (info->component != ShaderInterfaceVariableInfo::kInvalid)
     {
@@ -1463,6 +1564,11 @@ bool SpirvTransformer::transformDecorate(const uint32_t *instruction, size_t wor
         for (size_t i = 0; i < kXfbDecorationCount; ++i)
         {
             const size_t xfbInstructionOffset = copyInstruction(instruction, wordCount);
+            if (info->useRelaxedPrecision)
+            {
+                // Change the id to replacement variable
+                (*mSpirvBlobOut)[xfbInstructionOffset + kIdIndex] = mFixedVaryingId[id];
+            }
             (*mSpirvBlobOut)[xfbInstructionOffset + kDecorationIndex]      = xfbDecorations[i];
             (*mSpirvBlobOut)[xfbInstructionOffset + kDecorationValueIndex] = xfbDecorationValues[i];
         }
@@ -1518,6 +1624,7 @@ bool SpirvTransformer::transformEntryPoint(const uint32_t *instruction, size_t w
     // Remove inactive varyings from the shader interface declaration.
 
     // SPIR-V 1.0 Section 3.32 Instructions, OpEntryPoint
+    constexpr size_t kEntryPointIdIndex = 2;
     constexpr size_t kNameIndex         = 3;
 
     // Calculate the length of entry point name in words.  Note that endianness of the string
@@ -1529,6 +1636,10 @@ bool SpirvTransformer::transformEntryPoint(const uint32_t *instruction, size_t w
     const size_t interfaceStart      = kNameIndex + nameLength;
     const size_t interfaceCount      = instructionLength - interfaceStart;
 
+    // Should only have one EntryPoint
+    ASSERT(mEntryPointId == 0);
+    mEntryPointId = instruction[kEntryPointIdIndex];
+
     // Create a copy of the entry point for modification.
     std::vector<uint32_t> filteredEntryPoint(instruction, instruction + wordCount);
 
@@ -1546,6 +1657,11 @@ bool SpirvTransformer::transformEntryPoint(const uint32_t *instruction, size_t w
             continue;
         }
 
+        // If ID is one we had to replace due to varying mismatch, use the fixed ID.
+        if (mFixedVaryingId[id] != 0)
+        {
+            id = mFixedVaryingId[id];
+        }
         filteredEntryPoint[writeIndex] = id;
         ++writeIndex;
     }
@@ -1563,9 +1679,6 @@ bool SpirvTransformer::transformEntryPoint(const uint32_t *instruction, size_t w
         return true;
     }
 
-    // SPIR-V 1.0 Section 3.32 Instructions, OpEntryPoint
-    constexpr size_t kEntryPointIdIndex = 2;
-
     // SPIR-V 1.0 Section 3.32 Instructions, OpExecutionMode
     constexpr size_t kExecutionModeInstructionLength  = 3;
     constexpr size_t kExecutionModeIdIndex            = 1;
@@ -1599,38 +1712,66 @@ bool SpirvTransformer::transformTypePointer(const uint32_t *instruction, size_t
     // inactive varying, or if that varying is a struct, an Op*AccessChain retrieving a field of
     // that inactive varying.
     //
-    // Unfortunately, SPIR-V specifies the storage class both on the type and the variable
-    // declaration.  Otherwise it would have been sufficient to modify the OpVariable instruction.
-    // For simplicty, copy every "OpTypePointer Output" instruction except with the Private storage
-    // class, in case it may be necessary later.
+    // SPIR-V specifies the storage class both on the type and the variable declaration.  Otherwise
+    // it would have been sufficient to modify the OpVariable instruction. For simplicity, copy
+    // every "OpTypePointer Output" and "OpTypePointer Input" instruction except with the Private
+    // storage class, in case it may be necessary later.
 
-    if (storageClass != spv::StorageClassOutput)
+    // Cannot create a Private type declaration from builtins such as gl_PerVertex.
+    if (mNamesById[typeId] != nullptr && angle::BeginsWith(mNamesById[typeId], "gl_"))
     {
         return false;
     }
 
-    // Cannot create a Private type declaration from builtins such as gl_PerVertex.
-    if (mNamesById[typeId] != nullptr && angle::BeginsWith(mNamesById[typeId], "gl_"))
+    // Precision fixup needs this typeID
+    mTypePointerTransformedId[id].typeID = typeId;
+
+    if (storageClass != spv::StorageClassOutput && storageClass != spv::StorageClassInput)
     {
         return false;
     }
 
-    // Copy the type declaration for modification.
+    // Insert OpTypePointer definition for new PrivateType.
     const size_t instructionOffset = copyInstruction(instruction, wordCount);
 
-    const uint32_t newTypeId                                 = getNewId();
-    (*mSpirvBlobOut)[instructionOffset + kIdIndex]           = newTypeId;
+    const uint32_t newPrivateTypeId                          = getNewId();
+    (*mSpirvBlobOut)[instructionOffset + kIdIndex]           = newPrivateTypeId;
     (*mSpirvBlobOut)[instructionOffset + kStorageClassIndex] = spv::StorageClassPrivate;
 
     // Remember the id of the replacement.
     ASSERT(id < mTypePointerTransformedId.size());
-    mTypePointerTransformedId[id] = newTypeId;
+    mTypePointerTransformedId[id].privateID = newPrivateTypeId;
 
     // The original instruction should still be present as well.  At this point, we don't know
     // whether we will need the Output or Private type.
     return false;
 }
 
+bool SpirvTransformer::transformReturn(const uint32_t *instruction, size_t wordCount)
+{
+    if (mOpFunctionId != mEntryPointId)
+    {
+        // We only need to process the precision info when returning from the entry point function
+        return false;
+    }
+
+    for (uint32_t id = 0; id < mVariableInfoById.size(); id++)
+    {
+        const ShaderInterfaceVariableInfo *info = mVariableInfoById[id];
+        if (info && info->useRelaxedPrecision && info->activeStages[mShaderType] &&
+            info->varyingIsOutput)
+        {
+            // Build OpLoad instruction to load the highp value into a temporary
+            uint32_t tempVar = getNewId();
+            writeOpLoad(id, mFixedVaryingTypeId[id], tempVar);
+
+            // Build OpStore instruction to cast the highp value to mediump for output
+            writeOpStore(tempVar, mFixedVaryingId[id]);
+        }
+    }
+    return false;
+}
+
 bool SpirvTransformer::transformVariable(const uint32_t *instruction, size_t wordCount)
 {
     // SPIR-V 1.0 Section 3.32 Instructions, OpVariable
@@ -1656,6 +1797,21 @@ bool SpirvTransformer::transformVariable(const uint32_t *instruction, size_t wor
     ASSERT(storageClass != spv::StorageClassInput || info->activeStages[mShaderType]);
     if (info->activeStages[mShaderType])
     {
+        if (info->useRelaxedPrecision &&
+            (storageClass == spv::StorageClassOutput || storageClass == spv::StorageClassInput))
+        {
+            // Change existing OpVariable to use fixedVaryingId
+            const size_t instructionOffset = copyInstruction(instruction, wordCount);
+            ASSERT(mFixedVaryingId[id] != 0);
+            (*mSpirvBlobOut)[instructionOffset + kIdIndex] = mFixedVaryingId[id];
+
+            // Make original variable a private global
+            ASSERT(mTypePointerTransformedId[typeId].privateID != 0);
+            writeOpVariable(id, mTypePointerTransformedId[typeId].privateID,
+                            spv::StorageClassPrivate);
+
+            return true;
+        }
         return false;
     }
 
@@ -1667,9 +1823,10 @@ bool SpirvTransformer::transformVariable(const uint32_t *instruction, size_t wor
     const size_t instructionOffset = copyInstruction(instruction, wordCount);
 
     ASSERT(typeId < mTypePointerTransformedId.size());
-    ASSERT(mTypePointerTransformedId[typeId] != 0);
+    ASSERT(mTypePointerTransformedId[typeId].privateID != 0);
 
-    (*mSpirvBlobOut)[instructionOffset + kTypeIdIndex]       = mTypePointerTransformedId[typeId];
+    (*mSpirvBlobOut)[instructionOffset + kTypeIdIndex] =
+        mTypePointerTransformedId[typeId].privateID;
     (*mSpirvBlobOut)[instructionOffset + kStorageClassIndex] = spv::StorageClassPrivate;
 
     return true;
@@ -1687,18 +1844,23 @@ bool SpirvTransformer::transformAccessChain(const uint32_t *instruction, size_t
 
     // If not accessing an inactive output varying, nothing to do.
     const ShaderInterfaceVariableInfo *info = mVariableInfoById[baseId];
-    if (info == nullptr || info->activeStages[mShaderType])
+    if (info == nullptr)
     {
         return false;
     }
 
+    if (info->activeStages[mShaderType] && !info->useRelaxedPrecision)
+    {
+        return false;
+    }
     // Copy the instruction for modification.
     const size_t instructionOffset = copyInstruction(instruction, wordCount);
 
     ASSERT(typeId < mTypePointerTransformedId.size());
-    ASSERT(mTypePointerTransformedId[typeId] != 0);
+    ASSERT(mTypePointerTransformedId[typeId].privateID != 0);
 
-    (*mSpirvBlobOut)[instructionOffset + kTypeIdIndex] = mTypePointerTransformedId[typeId];
+    (*mSpirvBlobOut)[instructionOffset + kTypeIdIndex] =
+        mTypePointerTransformedId[typeId].privateID;
 
     return true;
 }
@@ -1730,6 +1892,57 @@ uint32_t SpirvTransformer::getNewId()
 {
     return (*mSpirvBlobOut)[kHeaderIndexIndexBound]++;
 }
+
+void SpirvTransformer::writeOpStore(uint32_t tempVarId, uint32_t destId)
+{
+    constexpr size_t kInstIndex                = 0;
+    constexpr size_t kIdIndex                  = 1;
+    constexpr size_t kObjectIndex              = 2;
+    constexpr size_t kOpStoreInstructionLength = 3;
+
+    uint32_t opStore[kOpStoreInstructionLength];
+    SetSpirvInstructionLength(&opStore[kInstIndex], kOpStoreInstructionLength);
+    SetSpirvInstructionOp(&opStore[kInstIndex], spv::OpStore);
+    opStore[kIdIndex]     = destId;
+    opStore[kObjectIndex] = tempVarId;
+    copyInstruction(opStore, kOpStoreInstructionLength);
+}
+
+void SpirvTransformer::writeOpLoad(uint32_t id, uint32_t typeId, uint32_t tempVarId)
+{
+    constexpr size_t kResultTypeIndex         = 1;
+    constexpr size_t kResultIdIndex           = 2;
+    constexpr size_t kLoadIdIndex             = 3;
+    constexpr size_t kOpLoadInstructionLength = 4;
+
+    // Build OpLoad instruction
+    ASSERT(typeId != 0);
+    ASSERT(mTypePointerTransformedId[typeId].typeID != 0);
+
+    uint32_t opLoad[kOpLoadInstructionLength];
+    SetSpirvInstructionOp(opLoad, spv::OpLoad);
+    SetSpirvInstructionLength(opLoad, kOpLoadInstructionLength);
+    opLoad[kResultTypeIndex] = mTypePointerTransformedId[typeId].typeID;
+    opLoad[kResultIdIndex]   = tempVarId;
+    opLoad[kLoadIdIndex]     = id;
+    copyInstruction(opLoad, kOpLoadInstructionLength);
+}
+
+void SpirvTransformer::writeOpVariable(uint32_t id, uint32_t typeId, uint32_t storageClassId)
+{
+    constexpr size_t kResultTypeIndex             = 1;
+    constexpr size_t kResultIdIndex               = 2;
+    constexpr size_t kStorageClassIdIndex         = 3;
+    constexpr size_t kOpVariableInstructionLength = 4;
+
+    uint32_t opVariable[kOpVariableInstructionLength];
+    SetSpirvInstructionOp(opVariable, spv::OpVariable);
+    SetSpirvInstructionLength(opVariable, kOpVariableInstructionLength);
+    opVariable[kResultTypeIndex]     = typeId;
+    opVariable[kResultIdIndex]       = id;
+    opVariable[kStorageClassIdIndex] = storageClassId;
+    copyInstruction(opVariable, kOpVariableInstructionLength);
+}
 }  // anonymous namespace
 
 const uint32_t ShaderInterfaceVariableInfo::kInvalid;

src/libANGLE/renderer/glslang_wrapper_utils.h

@@ -81,6 +81,13 @@ struct ShaderInterfaceVariableInfo
     uint32_t xfbBuffer = kInvalid;
     uint32_t xfbOffset = kInvalid;
     uint32_t xfbStride = kInvalid;
+    // Indicates that the precision needs to be modified in the generated SPIR-V
+    // to support only transferring medium precision data when there's a precision
+    // mismatch between the shaders. For example, either the VS casts highp->mediump
+    // or the FS casts mediump->highp.
+    bool useRelaxedPrecision = false;
+    // Indicate if varying is input or output
+    bool varyingIsOutput = false;
 };
 
 // TODO: http://anglebug.com/4524: Need a different hash key than a string, since

src/libANGLE/renderer/vulkan/ProgramExecutableVk.cpp

@@ -223,6 +223,8 @@ std::unique_ptr<rx::LinkEvent> ProgramExecutableVk::load(gl::BinaryInputStream *
             info->xfbBuffer           = stream->readInt<uint32_t>();
             info->xfbOffset           = stream->readInt<uint32_t>();
             info->xfbStride           = stream->readInt<uint32_t>();
+            info->useRelaxedPrecision = stream->readBool();
+            info->varyingIsOutput     = stream->readBool();
         }
     }
 
@@ -246,6 +248,8 @@ void ProgramExecutableVk::save(gl::BinaryOutputStream *stream)
             stream->writeInt<uint32_t>(it.second.xfbBuffer);
             stream->writeInt<uint32_t>(it.second.xfbOffset);
             stream->writeInt<uint32_t>(it.second.xfbStride);
+            stream->writeInt<uint8_t>(it.second.useRelaxedPrecision);
+            stream->writeInt<uint8_t>(it.second.varyingIsOutput);
         }
     }
 }
@@ -866,6 +870,40 @@ angle::Result ProgramExecutableVk::createPipelineLayout(const gl::Context *glCon
     return angle::Result::Continue;
 }
 
+void ProgramExecutableVk::resolvePrecisionMismatch(const gl::ProgramMergedVaryings &mergedVaryings)
+{
+    for (const gl::ProgramVaryingRef &mergedVarying : mergedVaryings)
+    {
+        if (mergedVarying.frontShader && mergedVarying.backShader)
+        {
+            GLenum frontPrecision = mergedVarying.frontShader->precision;
+            GLenum backPrecision  = mergedVarying.backShader->precision;
+            if (frontPrecision != backPrecision)
+            {
+                ShaderInterfaceVariableInfo *info =
+                    &mVariableInfoMap[mergedVarying.frontShaderStage]
+                                     [mergedVarying.frontShader->mappedName];
+                ASSERT(frontPrecision >= GL_LOW_FLOAT && frontPrecision <= GL_HIGH_INT);
+                ASSERT(backPrecision >= GL_LOW_FLOAT && backPrecision <= GL_HIGH_INT);
+                if (frontPrecision > backPrecision)
+                {
+                    // The output is higher precision than the input
+                    info->varyingIsOutput     = true;
+                    info->useRelaxedPrecision = true;
+                }
+                else if (backPrecision > frontPrecision)
+                {
+                    // The output is lower precision than the input, adjust the input
+                    info = &mVariableInfoMap[mergedVarying.backShaderStage]
+                                            [mergedVarying.backShader->mappedName];
+                    info->varyingIsOutput     = false;
+                    info->useRelaxedPrecision = true;
+                }
+            }
+        }
+    }
+}
+
 void ProgramExecutableVk::updateDefaultUniformsDescriptorSet(
     const gl::ShaderType shaderType,
     const DefaultUniformBlock &defaultUniformBlock,

src/libANGLE/renderer/vulkan/ProgramExecutableVk.h

@@ -197,6 +197,7 @@ class ProgramExecutableVk
                                      const gl::ActiveTextureArray<vk::TextureUnit> *activeTextures,
                                      vk::DescriptorSetLayoutDesc *descOut);
 
+    void resolvePrecisionMismatch(const gl::ProgramMergedVaryings &mergedVaryings);
     void updateDefaultUniformsDescriptorSet(const gl::ShaderType shaderType,
                                             const DefaultUniformBlock &defaultUniformBlock,
                                             vk::BufferHelper *defaultUniformBuffer,

src/libANGLE/renderer/vulkan/ProgramPipelineVk.cpp

@@ -53,7 +53,7 @@ void ProgramPipelineVk::fillProgramStateMap(
 }
 
 angle::Result ProgramPipelineVk::link(const gl::Context *glContext,
-                                      const gl::ProgramMergedVaryings & /*mergedVaryings*/)
+                                      const gl::ProgramMergedVaryings &mergedVaryings)
 {
     ContextVk *contextVk                  = vk::GetImpl(glContext);
     const gl::State &glState              = glContext->getState();
@@ -87,6 +87,11 @@ angle::Result ProgramPipelineVk::link(const gl::Context *glContext,
         }
     }
 
+    if (contextVk->getFeatures().enablePrecisionQualifiers.enabled)
+    {
+        mExecutable.resolvePrecisionMismatch(mergedVaryings);
+    }
+
     return mExecutable.createPipelineLayout(glContext);
 }
 

src/libANGLE/renderer/vulkan/ProgramVk.cpp

@@ -255,7 +255,7 @@ void ProgramVk::fillProgramStateMap(gl::ShaderMap<const gl::ProgramState *> *pro
 std::unique_ptr<LinkEvent> ProgramVk::link(const gl::Context *context,
                                            const gl::ProgramLinkedResources &resources,
                                            gl::InfoLog &infoLog,
-                                           const gl::ProgramMergedVaryings & /*mergedVaryings*/)
+                                           const gl::ProgramMergedVaryings &mergedVaryings)
 {
     ANGLE_TRACE_EVENT0("gpu.angle", "ProgramVk::link");
 
@@ -288,6 +288,11 @@ std::unique_ptr<LinkEvent> ProgramVk::link(const gl::Context *context,
         return std::make_unique<LinkEventDone>(status);
     }
 
+    if (contextVk->getFeatures().enablePrecisionQualifiers.enabled)
+    {
+        mExecutable.resolvePrecisionMismatch(mergedVaryings);
+    }
+
     // TODO(jie.a.chen@intel.com): Parallelize linking.
     // http://crbug.com/849576
     status = mExecutable.createPipelineLayout(context);

src/tests/gl_tests/GLSLTest.cpp

@@ -5932,6 +5932,220 @@ void main()
     EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
 }
 
+// Test mismatched precision in varying is handled correctly.
+TEST_P(GLSLTest_ES3, MismatchPrecisionFloat)
+{
+    constexpr char kVS[] = R"(#version 300 es
+in vec4 position;
+uniform highp float inVal;
+out highp float myVarying;
+
+void main()
+{
+    myVarying = inVal;
+    gl_Position = position;
+})";
+
+    constexpr char kFS[] = R"(#version 300 es
+precision highp float;
+out vec4 my_FragColor;
+in mediump float myVarying;
+
+void main()
+{
+    my_FragColor = vec4(1, 0, 0, 1);
+    if (myVarying > 1.0)
+    {
+        my_FragColor = vec4(0, 1, 0, 1);
+    }
+})";
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    glUseProgram(program.get());
+    GLint positionLocation              = glGetAttribLocation(program.get(), "position");
+    std::array<Vector3, 6> quadVertices = GetQuadVertices();
+    for (Vector3 &vertex : quadVertices)
+    {
+        vertex.z() = 0.5f;
+    }
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, quadVertices.data());
+    glEnableVertexAttribArray(positionLocation);
+
+    GLint inValLoc = glGetUniformLocation(program, "inVal");
+    ASSERT_NE(-1, inValLoc);
+    glUniform1f(inValLoc, static_cast<GLfloat>(1.003));
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
+// Test mismatched precision in varying is handled correctly.
+TEST_P(GLSLTest_ES3, MismatchPrecisionlowpFloat)
+{
+    // Note: SPIRV only has relaxed precision so both lowp and mediump turn into "relaxed
+    // precision", thus this is the same test as MismatchPrecisionFloat but including it for
+    // completeness in case something changes.
+    constexpr char kVS[] = R"(#version 300 es
+in vec4 position;
+uniform highp float inVal;
+out highp float myVarying;
+
+void main()
+{
+    myVarying = inVal;
+    gl_Position = position;
+})";
+
+    constexpr char kFS[] = R"(#version 300 es
+precision highp float;
+out vec4 my_FragColor;
+in lowp float myVarying;
+
+void main()
+{
+    my_FragColor = vec4(1, 0, 0, 1);
+    if (myVarying > 1.0)
+    {
+        my_FragColor = vec4(0, 1, 0, 1);
+    }
+})";
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    glUseProgram(program.get());
+    GLint positionLocation              = glGetAttribLocation(program.get(), "position");
+    std::array<Vector3, 6> quadVertices = GetQuadVertices();
+    for (Vector3 &vertex : quadVertices)
+    {
+        vertex.z() = 0.5f;
+    }
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, quadVertices.data());
+    glEnableVertexAttribArray(positionLocation);
+
+    GLint inValLoc = glGetUniformLocation(program, "inVal");
+    ASSERT_NE(-1, inValLoc);
+    glUniform1f(inValLoc, static_cast<GLfloat>(1.003));
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
+// Test mismatched precision in varying is handled correctly.
+TEST_P(GLSLTest_ES3, MismatchPrecisionVec2UnusedVarying)
+{
+    constexpr char kVS[] = R"(#version 300 es
+in vec2 position;
+uniform highp float inVal;
+out highp float myVarying;
+out highp vec2 texCoord;
+
+void main()
+{
+    myVarying = inVal;
+    gl_Position = vec4(position, 0, 1);
+    texCoord = position * 0.5 + vec2(0.5);
+})";
+
+    constexpr char kFS[] = R"(#version 300 es
+precision highp float;
+out vec4 my_FragColor;
+in mediump float myVarying;
+in mediump vec2 texCoord;
+
+void main()
+{
+    my_FragColor = vec4(1, 0, 0, 1);
+    if (myVarying > 1.0)
+    {
+        my_FragColor = vec4(0, 1, 0, 1);
+    }
+})";
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    glUseProgram(program.get());
+    GLint positionLocation              = glGetAttribLocation(program.get(), "position");
+    std::array<Vector3, 6> quadVertices = GetQuadVertices();
+    for (Vector3 &vertex : quadVertices)
+    {
+        vertex.z() = 0.5f;
+    }
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, quadVertices.data());
+    glEnableVertexAttribArray(positionLocation);
+
+    GLint inValLoc = glGetUniformLocation(program, "inVal");
+    ASSERT_NE(-1, inValLoc);
+    glUniform1f(inValLoc, static_cast<GLfloat>(1.003));
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
+// Test mismatched precision in varying is handled correctly.
+TEST_P(GLSLTest_ES3, MismatchPrecisionMedToHigh)
+{
+    constexpr char kVS[] = R"(#version 300 es
+in vec2 position;
+uniform highp float inVal;
+out mediump float myVarying;
+
+void main()
+{
+    myVarying = inVal;
+    gl_Position = vec4(position, 0, 1);
+})";
+
+    constexpr char kFS[] = R"(#version 300 es
+precision highp float;
+out vec4 my_FragColor;
+in highp float myVarying;
+
+void main()
+{
+    my_FragColor = vec4(1, 0, 0, 1);
+    if (myVarying > 1.0)
+    {
+        my_FragColor = vec4(0, 1, 0, 1);
+    }
+})";
+
+    ANGLE_GL_PROGRAM(program, kVS, kFS);
+
+    glClearColor(1.0f, 0.0f, 0.0f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::red);
+
+    glUseProgram(program.get());
+    GLint positionLocation              = glGetAttribLocation(program.get(), "position");
+    std::array<Vector3, 6> quadVertices = GetQuadVertices();
+    for (Vector3 &vertex : quadVertices)
+    {
+        vertex.z() = 0.5f;
+    }
+    glVertexAttribPointer(positionLocation, 3, GL_FLOAT, GL_FALSE, 0, quadVertices.data());
+    glEnableVertexAttribArray(positionLocation);
+
+    GLint inValLoc = glGetUniformLocation(program, "inVal");
+    ASSERT_NE(-1, inValLoc);
+    glUniform1f(inValLoc, static_cast<GLfloat>(1.003));
+
+    glDrawArrays(GL_TRIANGLES, 0, 6);
+    EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::green);
+}
+
 // Test vector/scalar arithmetic (in this case multiplication and addition). Meant to reproduce a
 // bug that appeared in NVIDIA OpenGL drivers and that is worked around by
 // VectorizeVectorScalarArithmetic AST transform.