Hash :
800e82c6
Author :
Date :
2021-08-23T11:05:23
Translator: Validate precisions
When declaring a variable, a struct field, function parameter etc,
there's a precision necessarily applied to the entity being declared.
AST Validation is added to enforce this. Intermediate nodes derive
their precision from these entities automatically.
Consistency of intermediate nodes is not validated. This is because AST
transformations replace a node with a transformed one, and that may not
have the same precision. Take the following code:
mediump float x = ...;
mediump float y = ...;
... x + y ...
and assume is transformed as such:
highp float driver_uniform;
... (x * driver_uniform) + y ...
The addition was originally done in mediump, but would seemingly need to
be done in highp after transformation. There are a number of options
here:
- Make sure that when nodes are replaced, the precision is unaffected.
This can be intrusive, requiring temp variables.
- Bubble up the new precision
- Accept the discrepancy
ANGLE opts for the last option, which actually respects the original
shader's intended precision for operations, even if some transformation
needs to temporarily evaluate an expression at a higher precision.
Bug: angleproject:4889
Bug: angleproject:6132
Change-Id: Ibcde3a230de159157783b1c6d5ef1cd63ceb4d8f
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3114027
Reviewed-by: Tim Van Patten <timvp@google.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org>
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//
// Copyright 2019 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.
//
#ifndef COMPILER_TRANSLATOR_VALIDATEAST_H_
#define COMPILER_TRANSLATOR_VALIDATEAST_H_
#include "compiler/translator/BaseTypes.h"
#include "compiler/translator/Common.h"
namespace sh
{
class TDiagnostics;
class TIntermNode;
// The following options (stored in Compiler) tell the validator what to validate. Some validations
// are conditional to certain passes.
struct ValidateASTOptions
{
// TODO: add support for the flags marked with TODO. http://anglebug.com/2733
// Check that every node always has only one parent,
bool validateSingleParent = true;
// Check that all symbols reference TVariables that have been declared. For built-ins, this
// makes sure that the same GLSL built-in uses the same TVariable consistently.
bool validateVariableReferences = true;
// Whether validateVariableReferences should also include specialization constants. Their
// declaration is output after their usage is discovered, so this is disabled until then.
bool validateSpecConstReferences = false;
// Check that TIntermUnary and TIntermAggregate nodes with a built-in op reference a function
// with said op.
bool validateBuiltInOps = true;
// Check that all EOpCallFunctionInAST have their corresponding function definitions in the AST,
// with matching symbol ids. There should also be at least a prototype declaration before the
// function is called.
bool validateFunctionCall = true;
// Check that EOpCallInternalRawFunction is not used. This OP is deprecated and needs to be
// removed. http://anglebug.com/6059
bool validateNoRawFunctionCalls = true;
// Check that there are no null nodes where they are not allowed, for example as children of
// TIntermDeclaration or TIntermBlock.
bool validateNullNodes = true;
// Check that symbols that reference variables have consistent qualifiers and symbol ids with
// the variable declaration. The following needs to be validated:
//
// Implemented:
//
// - Function parameters having one of EvqParam* qualifiers.
// - gl_ClipDistance, gl_CullDistance and gl_LastFragData are correctly qualified even when
// redeclared in the shader.
//
// TODO:
//
// - Function-local variables must have the EvqTemporary qualifier.
// - Symbol references and declarations have identical qualifiers.
bool validateQualifiers = true;
// Check that every symbol has its precision specified. That includes variables, block members,
// function parameters and return values.
bool validatePrecision = true;
// Check that variable declarations that can't have initializers don't have initializers
// (varyings, uniforms for example).
bool validateInitializers = true; // TODO
// Check that there is only one TFunction with each function name referenced in the nodes (no
// two TFunctions with the same name, taking internal/non-internal namespaces into account).
bool validateUniqueFunctions = true; // TODO
// Check that references to structs are matched with the corresponding struct declaration. This
// is only done for references to structs inside other struct or interface blocks declarations,
// as validateVariableReferences already ensures other references to the struct match the
// declaration.
bool validateStructUsage = true;
// Check that expression nodes have the correct type considering their operand(s). The
// following validation is possible:
//
// Implemented:
//
// - Binary node that indexes T[] should have type T
//
// TODO:
//
// - Function calls (including built-ins) have the same return type in the node and function.
// - Unary and binary operators have the correct type based on operands
// - Swizzle result has same type as the operand except for vector size
// - Ternary operator has the same type as the operands
bool validateExpressionTypes = true;
// If SeparateDeclarations has been run, check for the absence of multi declarations as well.
bool validateMultiDeclarations = false;
// Once set, disallows any further transformations on the tree. Used before AST post-processing
// which requires that the tree remains unmodified.
bool validateNoMoreTransformations = false;
};
// Check for errors and output error messages on the context.
// Returns true if there are no errors.
bool ValidateAST(TIntermNode *root, TDiagnostics *diagnostics, const ValidateASTOptions &options);
} // namespace sh
#endif // COMPILER_TRANSLATOR_VALIDATESWITCH_H_