propagateNoContraction.cpp | Explore in Territory

//
// Copyright (C) 2015-2016 Google, Inc.
//
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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// CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
// ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
// POSSIBILITY OF SUCH DAMAGE.

//
// Visit the nodes in the glslang intermediate tree representation to
// propagate the 'noContraction' qualifier.
//

#include "propagateNoContraction.h"

#include <cstdlib>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>

#include "localintermediate.h"
namespace {

// Use a string to hold the access chain information, as in most cases the
// access chain is short and may contain only one element, which is the symbol
// ID.
// Example: struct {float a; float b;} s;
//  Object s.a will be represented with: <symbol ID of s>/0
//  Object s.b will be represented with: <symbol ID of s>/1
//  Object s will be represented with: <symbol ID of s>
// For members of vector, matrix and arrays, they will be represented with the
// same symbol ID of their container symbol objects. This is because their
// preciseness is always the same as their container symbol objects.
ObjectAccessChain;

// The delimiter used in the ObjectAccessChain string to separate symbol ID and
// different level of struct indices.
const char ObjectAccesschainDelimiter = …;

// Mapping from Symbol IDs of symbol nodes, to their defining operation
// nodes.
NodeMapping;
// Mapping from object nodes to their access chain info string.
AccessChainMapping;

// Set of object IDs.
ObjectAccesschainSet;
// Set of return branch nodes.
ReturnBranchNodeSet;

// A helper function to tell whether a node is 'noContraction'. Returns true if
// the node has 'noContraction' qualifier, otherwise false.
bool isPreciseObjectNode(glslang::TIntermTyped* node)
{ … }

// Returns true if the opcode is a dereferencing one.
bool isDereferenceOperation(glslang::TOperator op)
{ … }

// Returns true if the opcode leads to an assignment operation.
bool isAssignOperation(glslang::TOperator op)
{ … }

// A helper function to get the unsigned int from a given constant union node.
// Note the node should only hold a uint scalar.
unsigned getStructIndexFromConstantUnion(glslang::TIntermTyped* node)
{ … }

// A helper function to generate symbol_label.
ObjectAccessChain generateSymbolLabel(glslang::TIntermSymbol* node)
{ … }

// Returns true if the operation is an arithmetic operation and valid for
// the 'NoContraction' decoration.
bool isArithmeticOperation(glslang::TOperator op)
{ … }

// A helper class to help manage the populating_initial_no_contraction_ flag.
template <typename T> class StateSettingGuard { … };

// A helper function to get the front element from a given ObjectAccessChain
ObjectAccessChain getFrontElement(const ObjectAccessChain& chain)
{ … }

// A helper function to get the access chain starting from the second element.
ObjectAccessChain subAccessChainFromSecondElement(const ObjectAccessChain& chain)
{ … }

// A helper function to get the access chain after removing a given prefix.
ObjectAccessChain getSubAccessChainAfterPrefix(const ObjectAccessChain& chain,
                                               const ObjectAccessChain& prefix)
{ … }

//
// A traverser which traverses the whole AST and populates:
//  1) A mapping from symbol nodes' IDs to their defining operation nodes.
//  2) A set of access chains of the initial precise object nodes.
//
class TSymbolDefinitionCollectingTraverser : public glslang::TIntermTraverser { … };

TSymbolDefinitionCollectingTraverser::TSymbolDefinitionCollectingTraverser(
    NodeMapping* symbol_definition_mapping, AccessChainMapping* accesschain_mapping,
    ObjectAccesschainSet* precise_objects,
    std::unordered_set<glslang::TIntermBranch*>* precise_return_nodes)
    : … { … }

// Visits a symbol node, set the current_object_ to the
// current node symbol ID, and record a mapping from this node to the current
// current_object_, which is the just obtained symbol
// ID.
void TSymbolDefinitionCollectingTraverser::visitSymbol(glslang::TIntermSymbol* node)
{ … }

// Visits an aggregate node, traverses all of its children.
bool TSymbolDefinitionCollectingTraverser::visitAggregate(glslang::TVisit,
                                                          glslang::TIntermAggregate* node)
{ … }

bool TSymbolDefinitionCollectingTraverser::visitBranch(glslang::TVisit,
                                                       glslang::TIntermBranch* node)
{ … }

// Visits a unary node. This might be an implicit assignment like i++, i--. etc.
bool TSymbolDefinitionCollectingTraverser::visitUnary(glslang::TVisit /* visit */,
                                                      glslang::TIntermUnary* node)
{ … }

// Visits a binary node and updates the mapping from symbol IDs to the definition
// nodes. Also collects the access chains for the initial precise objects.
bool TSymbolDefinitionCollectingTraverser::visitBinary(glslang::TVisit /* visit */,
                                                       glslang::TIntermBinary* node)
{ … }

// Traverses the AST and returns a tuple of four members:
// 1) a mapping from symbol IDs to the definition nodes (aka. assignment nodes) of these symbols.
// 2) a mapping from object nodes in the AST to the access chains of these objects.
// 3) a set of access chains of precise objects.
// 4) a set of return nodes with precise expressions.
std::tuple<NodeMapping, AccessChainMapping, ObjectAccesschainSet, ReturnBranchNodeSet>
getSymbolToDefinitionMappingAndPreciseSymbolIDs(const glslang::TIntermediate& intermediate)
{ … }

//
// A traverser that determine whether the left node (or operand node for unary
// node) of an assignment node is 'precise', containing 'precise' or not,
// according to the access chain a given precise object which share the same
// symbol as the left node.
//
// Post-orderly traverses the left node subtree of an binary assignment node and:
//
//  1) Propagates the 'precise' from the left object nodes to this object node.
//
//  2) Builds object access chain along the traversal, and also compares with
//  the access chain of the given 'precise' object along with the traversal to
//  tell if the node to be defined is 'precise' or not.
//
class TNoContractionAssigneeCheckingTraverser : public glslang::TIntermTraverser { … };

// Visits a binary node. If the node is an object node, it must be a dereference
// node. In such cases, if the left node is 'precise', this node should also be
// 'precise'.
bool TNoContractionAssigneeCheckingTraverser::visitBinary(glslang::TVisit,
                                                          glslang::TIntermBinary* node)
{ … }

// Visits a symbol node, if the symbol node ID (its access chain string) matches
// with the given precise object, this node should be 'precise'.
void TNoContractionAssigneeCheckingTraverser::visitSymbol(glslang::TIntermSymbol* node)
{ … }

//
// A traverser that only traverses the right side of binary assignment nodes
// and the operand node of unary assignment nodes.
//
// 1) Marks arithmetic operations as 'NoContraction'.
//
// 2) Find the object which should be marked as 'precise' in the right and
//    update the 'precise' object work list.
//
class TNoContractionPropagator : public glslang::TIntermTraverser { … };
}

namespace glslang {

void PropagateNoContraction(const glslang::TIntermediate& intermediate)
{ … }
}
chromium/third_party/glslang/src/glslang/MachineIndependent/propagateNoContraction.cpp
