/*
* Copyright 2016 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "SkSLCFGGenerator.h"
#include "ir/SkSLConstructor.h"
#include "ir/SkSLBinaryExpression.h"
#include "ir/SkSLDoStatement.h"
#include "ir/SkSLExpressionStatement.h"
#include "ir/SkSLFieldAccess.h"
#include "ir/SkSLForStatement.h"
#include "ir/SkSLFunctionCall.h"
#include "ir/SkSLIfStatement.h"
#include "ir/SkSLIndexExpression.h"
#include "ir/SkSLPostfixExpression.h"
#include "ir/SkSLPrefixExpression.h"
#include "ir/SkSLReturnStatement.h"
#include "ir/SkSLSwizzle.h"
#include "ir/SkSLSwitchStatement.h"
#include "ir/SkSLTernaryExpression.h"
#include "ir/SkSLVarDeclarationsStatement.h"
#include "ir/SkSLWhileStatement.h"
namespace SkSL {
BlockId CFG::newBlock() {
BlockId result = fBlocks.size();
fBlocks.emplace_back();
if (fBlocks.size() > 1) {
this->addExit(fCurrent, result);
}
fCurrent = result;
return result;
}
BlockId CFG::newIsolatedBlock() {
BlockId result = fBlocks.size();
fBlocks.emplace_back();
return result;
}
void CFG::addExit(BlockId from, BlockId to) {
if (from == 0 || fBlocks[from].fEntrances.size()) {
fBlocks[from].fExits.insert(to);
fBlocks[to].fEntrances.insert(from);
}
}
void CFG::dump() {
for (size_t i = 0; i < fBlocks.size(); i++) {
printf("Block %d\n-------\nBefore: ", (int) i);
const char* separator = "";
for (auto iter = fBlocks[i].fBefore.begin(); iter != fBlocks[i].fBefore.end(); iter++) {
printf("%s%s = %s", separator, iter->first->description().c_str(),
iter->second ? (*iter->second)->description().c_str() : "<undefined>");
separator = ", ";
}
printf("\nEntrances: ");
separator = "";
for (BlockId b : fBlocks[i].fEntrances) {
printf("%s%d", separator, (int) b);
separator = ", ";
}
printf("\n");
for (size_t j = 0; j < fBlocks[i].fNodes.size(); j++) {
BasicBlock::Node& n = fBlocks[i].fNodes[j];
printf("Node %d (%p): %s\n", (int) j, &n, n.fKind == BasicBlock::Node::kExpression_Kind
? (*n.expression())->description().c_str()
: (*n.statement())->description().c_str());
}
printf("Exits: ");
separator = "";
for (BlockId b : fBlocks[i].fExits) {
printf("%s%d", separator, (int) b);
separator = ", ";
}
printf("\n\n");
}
}
bool BasicBlock::tryRemoveExpressionBefore(std::vector<BasicBlock::Node>::iterator* iter,
Expression* e) {
if (e->fKind == Expression::kTernary_Kind) {
return false;
}
bool result;
if ((*iter)->fKind == BasicBlock::Node::kExpression_Kind) {
SkASSERT((*iter)->expression()->get() != e);
Expression* old = (*iter)->expression()->get();
do {
if ((*iter) == fNodes.begin()) {
return false;
}
--(*iter);
} while ((*iter)->fKind != BasicBlock::Node::kExpression_Kind ||
(*iter)->expression()->get() != e);
result = this->tryRemoveExpression(iter);
while ((*iter)->fKind != BasicBlock::Node::kExpression_Kind ||
(*iter)->expression()->get() != old) {
SkASSERT(*iter != fNodes.end());
++(*iter);
}
} else {
Statement* old = (*iter)->statement()->get();
do {
if ((*iter) == fNodes.begin()) {
return false;
}
--(*iter);
} while ((*iter)->fKind != BasicBlock::Node::kExpression_Kind ||
(*iter)->expression()->get() != e);
result = this->tryRemoveExpression(iter);
while ((*iter)->fKind != BasicBlock::Node::kStatement_Kind ||
(*iter)->statement()->get() != old) {
SkASSERT(*iter != fNodes.end());
++(*iter);
}
}
return result;
}
bool BasicBlock::tryRemoveLValueBefore(std::vector<BasicBlock::Node>::iterator* iter,
Expression* lvalue) {
switch (lvalue->fKind) {
case Expression::kVariableReference_Kind:
return true;
case Expression::kSwizzle_Kind:
return this->tryRemoveLValueBefore(iter, ((Swizzle*) lvalue)->fBase.get());
case Expression::kFieldAccess_Kind:
return this->tryRemoveLValueBefore(iter, ((FieldAccess*) lvalue)->fBase.get());
case Expression::kIndex_Kind:
if (!this->tryRemoveLValueBefore(iter, ((IndexExpression*) lvalue)->fBase.get())) {
return false;
}
return this->tryRemoveExpressionBefore(iter, ((IndexExpression*) lvalue)->fIndex.get());
case Expression::kTernary_Kind:
if (!this->tryRemoveExpressionBefore(iter,
((TernaryExpression*) lvalue)->fTest.get())) {
return false;
}
if (!this->tryRemoveLValueBefore(iter, ((TernaryExpression*) lvalue)->fIfTrue.get())) {
return false;
}
return this->tryRemoveLValueBefore(iter, ((TernaryExpression*) lvalue)->fIfFalse.get());
default:
ABORT("invalid lvalue: %s\n", lvalue->description().c_str());
}
}
bool BasicBlock::tryRemoveExpression(std::vector<BasicBlock::Node>::iterator* iter) {
Expression* expr = (*iter)->expression()->get();
switch (expr->fKind) {
case Expression::kBinary_Kind: {
BinaryExpression* b = (BinaryExpression*) expr;
if (b->fOperator == Token::EQ) {
if (!this->tryRemoveLValueBefore(iter, b->fLeft.get())) {
return false;
}
} else if (!this->tryRemoveExpressionBefore(iter, b->fLeft.get())) {
return false;
}
if (!this->tryRemoveExpressionBefore(iter, b->fRight.get())) {
return false;
}
SkASSERT((*iter)->expression()->get() == expr);
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kTernary_Kind: {
// ternaries cross basic block boundaries, must regenerate the CFG to remove it
return false;
}
case Expression::kFieldAccess_Kind: {
FieldAccess* f = (FieldAccess*) expr;
if (!this->tryRemoveExpressionBefore(iter, f->fBase.get())) {
return false;
}
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kSwizzle_Kind: {
Swizzle* s = (Swizzle*) expr;
if (!this->tryRemoveExpressionBefore(iter, s->fBase.get())) {
return false;
}
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kIndex_Kind: {
IndexExpression* idx = (IndexExpression*) expr;
if (!this->tryRemoveExpressionBefore(iter, idx->fBase.get())) {
return false;
}
if (!this->tryRemoveExpressionBefore(iter, idx->fIndex.get())) {
return false;
}
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kConstructor_Kind: {
Constructor* c = (Constructor*) expr;
for (auto& arg : c->fArguments) {
if (!this->tryRemoveExpressionBefore(iter, arg.get())) {
return false;
}
SkASSERT((*iter)->expression()->get() == expr);
}
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kFunctionCall_Kind: {
FunctionCall* f = (FunctionCall*) expr;
for (auto& arg : f->fArguments) {
if (!this->tryRemoveExpressionBefore(iter, arg.get())) {
return false;
}
SkASSERT((*iter)->expression()->get() == expr);
}
*iter = fNodes.erase(*iter);
return true;
}
case Expression::kPrefix_Kind:
if (!this->tryRemoveExpressionBefore(iter,
((PrefixExpression*) expr)->fOperand.get())) {
return false;
}
*iter = fNodes.erase(*iter);
return true;
case Expression::kPostfix_Kind:
if (!this->tryRemoveExpressionBefore(iter,
((PrefixExpression*) expr)->fOperand.get())) {
return false;
}
*iter = fNodes.erase(*iter);
return true;
case Expression::kBoolLiteral_Kind: // fall through
case Expression::kFloatLiteral_Kind: // fall through
case Expression::kIntLiteral_Kind: // fall through
case Expression::kSetting_Kind: // fall through
case Expression::kVariableReference_Kind:
*iter = fNodes.erase(*iter);
return true;
default:
ABORT("unhandled expression: %s\n", expr->description().c_str());
}
}
bool BasicBlock::tryInsertExpression(std::vector<BasicBlock::Node>::iterator* iter,
std::unique_ptr<Expression>* expr) {
switch ((*expr)->fKind) {
case Expression::kBinary_Kind: {
BinaryExpression* b = (BinaryExpression*) expr->get();
if (!this->tryInsertExpression(iter, &b->fRight)) {
return false;
}
++(*iter);
if (!this->tryInsertExpression(iter, &b->fLeft)) {
return false;
}
++(*iter);
BasicBlock::Node node = { BasicBlock::Node::kExpression_Kind, true, expr, nullptr };
*iter = fNodes.insert(*iter, node);
return true;
}
case Expression::kBoolLiteral_Kind: // fall through
case Expression::kFloatLiteral_Kind: // fall through
case Expression::kIntLiteral_Kind: // fall through
case Expression::kVariableReference_Kind: {
BasicBlock::Node node = { BasicBlock::Node::kExpression_Kind, true, expr, nullptr };
*iter = fNodes.insert(*iter, node);
return true;
}
case Expression::kConstructor_Kind: {
Constructor* c = (Constructor*) expr->get();
for (auto& arg : c->fArguments) {
if (!this->tryInsertExpression(iter, &arg)) {
return false;
}
++(*iter);
}
BasicBlock::Node node = { BasicBlock::Node::kExpression_Kind, true, expr, nullptr };
*iter = fNodes.insert(*iter, node);
return true;
}
default:
return false;
}
}
void CFGGenerator::addExpression(CFG& cfg, std::unique_ptr<Expression>* e, bool constantPropagate) {
SkASSERT(e);
switch ((*e)->fKind) {
case Expression::kBinary_Kind: {
BinaryExpression* b = (BinaryExpression*) e->get();
switch (b->fOperator) {
case Token::LOGICALAND: // fall through
case Token::LOGICALOR: {
// this isn't as precise as it could be -- we don't bother to track that if we
// early exit from a logical and/or, we know which branch of an 'if' we're going
// to hit -- but it won't make much difference in practice.
this->addExpression(cfg, &b->fLeft, constantPropagate);
BlockId start = cfg.fCurrent;
cfg.newBlock();
this->addExpression(cfg, &b->fRight, constantPropagate);
cfg.newBlock();
cfg.addExit(start, cfg.fCurrent);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({
BasicBlock::Node::kExpression_Kind,
constantPropagate,
e,
nullptr
});
break;
}
case Token::EQ: {
this->addExpression(cfg, &b->fRight, constantPropagate);
this->addLValue(cfg, &b->fLeft);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({
BasicBlock::Node::kExpression_Kind,
constantPropagate,
e,
nullptr
});
break;
}
default:
this->addExpression(cfg, &b->fLeft, !Compiler::IsAssignment(b->fOperator));
this->addExpression(cfg, &b->fRight, constantPropagate);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({
BasicBlock::Node::kExpression_Kind,
constantPropagate,
e,
nullptr
});
}
break;
}
case Expression::kConstructor_Kind: {
Constructor* c = (Constructor*) e->get();
for (auto& arg : c->fArguments) {
this->addExpression(cfg, &arg, constantPropagate);
}
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
}
case Expression::kFunctionCall_Kind: {
FunctionCall* c = (FunctionCall*) e->get();
for (auto& arg : c->fArguments) {
this->addExpression(cfg, &arg, constantPropagate);
}
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
}
case Expression::kFieldAccess_Kind:
this->addExpression(cfg, &((FieldAccess*) e->get())->fBase, constantPropagate);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
case Expression::kIndex_Kind:
this->addExpression(cfg, &((IndexExpression*) e->get())->fBase, constantPropagate);
this->addExpression(cfg, &((IndexExpression*) e->get())->fIndex, constantPropagate);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
case Expression::kPrefix_Kind: {
PrefixExpression* p = (PrefixExpression*) e->get();
this->addExpression(cfg, &p->fOperand, constantPropagate &&
p->fOperator != Token::PLUSPLUS &&
p->fOperator != Token::MINUSMINUS);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
}
case Expression::kPostfix_Kind:
this->addExpression(cfg, &((PostfixExpression*) e->get())->fOperand, false);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
case Expression::kSwizzle_Kind:
this->addExpression(cfg, &((Swizzle*) e->get())->fBase, constantPropagate);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
case Expression::kAppendStage_Kind: // fall through
case Expression::kBoolLiteral_Kind: // fall through
case Expression::kFloatLiteral_Kind: // fall through
case Expression::kIntLiteral_Kind: // fall through
case Expression::kSetting_Kind: // fall through
case Expression::kVariableReference_Kind:
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
break;
case Expression::kTernary_Kind: {
TernaryExpression* t = (TernaryExpression*) e->get();
this->addExpression(cfg, &t->fTest, constantPropagate);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kExpression_Kind,
constantPropagate, e, nullptr });
BlockId start = cfg.fCurrent;
cfg.newBlock();
this->addExpression(cfg, &t->fIfTrue, constantPropagate);
BlockId next = cfg.newBlock();
cfg.fCurrent = start;
cfg.newBlock();
this->addExpression(cfg, &t->fIfFalse, constantPropagate);
cfg.addExit(cfg.fCurrent, next);
cfg.fCurrent = next;
break;
}
case Expression::kFunctionReference_Kind: // fall through
case Expression::kTypeReference_Kind: // fall through
case Expression::kDefined_Kind:
SkASSERT(false);
break;
}
}
// adds expressions that are evaluated as part of resolving an lvalue
void CFGGenerator::addLValue(CFG& cfg, std::unique_ptr<Expression>* e) {
switch ((*e)->fKind) {
case Expression::kFieldAccess_Kind:
this->addLValue(cfg, &((FieldAccess&) **e).fBase);
break;
case Expression::kIndex_Kind:
this->addLValue(cfg, &((IndexExpression&) **e).fBase);
this->addExpression(cfg, &((IndexExpression&) **e).fIndex, true);
break;
case Expression::kSwizzle_Kind:
this->addLValue(cfg, &((Swizzle&) **e).fBase);
break;
case Expression::kVariableReference_Kind:
break;
case Expression::kTernary_Kind:
this->addExpression(cfg, &((TernaryExpression&) **e).fTest, true);
// Technically we will of course only evaluate one or the other, but if the test turns
// out to be constant, the ternary will get collapsed down to just one branch anyway. So
// it should be ok to pretend that we always evaluate both branches here.
this->addLValue(cfg, &((TernaryExpression&) **e).fIfTrue);
this->addLValue(cfg, &((TernaryExpression&) **e).fIfFalse);
break;
default:
// not an lvalue, can't happen
SkASSERT(false);
break;
}
}
void CFGGenerator::addStatement(CFG& cfg, std::unique_ptr<Statement>* s) {
switch ((*s)->fKind) {
case Statement::kBlock_Kind:
for (auto& child : ((Block&) **s).fStatements) {
addStatement(cfg, &child);
}
break;
case Statement::kIf_Kind: {
IfStatement& ifs = (IfStatement&) **s;
this->addExpression(cfg, &ifs.fTest, true);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
BlockId start = cfg.fCurrent;
cfg.newBlock();
this->addStatement(cfg, &ifs.fIfTrue);
BlockId next = cfg.newBlock();
if (ifs.fIfFalse) {
cfg.fCurrent = start;
cfg.newBlock();
this->addStatement(cfg, &ifs.fIfFalse);
cfg.addExit(cfg.fCurrent, next);
cfg.fCurrent = next;
} else {
cfg.addExit(start, next);
}
break;
}
case Statement::kExpression_Kind: {
this->addExpression(cfg, &((ExpressionStatement&) **s).fExpression, true);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
break;
}
case Statement::kVarDeclarations_Kind: {
VarDeclarationsStatement& decls = ((VarDeclarationsStatement&) **s);
for (auto& stmt : decls.fDeclaration->fVars) {
if (stmt->fKind == Statement::kNop_Kind) {
continue;
}
VarDeclaration& vd = (VarDeclaration&) *stmt;
if (vd.fValue) {
this->addExpression(cfg, &vd.fValue, true);
}
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind,
false, nullptr, &stmt });
}
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
break;
}
case Statement::kDiscard_Kind:
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
cfg.fCurrent = cfg.newIsolatedBlock();
break;
case Statement::kReturn_Kind: {
ReturnStatement& r = ((ReturnStatement&) **s);
if (r.fExpression) {
this->addExpression(cfg, &r.fExpression, true);
}
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
cfg.fCurrent = cfg.newIsolatedBlock();
break;
}
case Statement::kBreak_Kind:
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
cfg.addExit(cfg.fCurrent, fLoopExits.top());
cfg.fCurrent = cfg.newIsolatedBlock();
break;
case Statement::kContinue_Kind:
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
cfg.addExit(cfg.fCurrent, fLoopContinues.top());
cfg.fCurrent = cfg.newIsolatedBlock();
break;
case Statement::kWhile_Kind: {
WhileStatement& w = (WhileStatement&) **s;
BlockId loopStart = cfg.newBlock();
fLoopContinues.push(loopStart);
BlockId loopExit = cfg.newIsolatedBlock();
fLoopExits.push(loopExit);
this->addExpression(cfg, &w.fTest, true);
BlockId test = cfg.fCurrent;
cfg.addExit(test, loopExit);
cfg.newBlock();
this->addStatement(cfg, &w.fStatement);
cfg.addExit(cfg.fCurrent, loopStart);
fLoopContinues.pop();
fLoopExits.pop();
cfg.fCurrent = loopExit;
break;
}
case Statement::kDo_Kind: {
DoStatement& d = (DoStatement&) **s;
BlockId loopStart = cfg.newBlock();
fLoopContinues.push(loopStart);
BlockId loopExit = cfg.newIsolatedBlock();
fLoopExits.push(loopExit);
this->addStatement(cfg, &d.fStatement);
this->addExpression(cfg, &d.fTest, true);
cfg.addExit(cfg.fCurrent, loopExit);
cfg.addExit(cfg.fCurrent, loopStart);
fLoopContinues.pop();
fLoopExits.pop();
cfg.fCurrent = loopExit;
break;
}
case Statement::kFor_Kind: {
ForStatement& f = (ForStatement&) **s;
if (f.fInitializer) {
this->addStatement(cfg, &f.fInitializer);
}
BlockId loopStart = cfg.newBlock();
BlockId next = cfg.newIsolatedBlock();
fLoopContinues.push(next);
BlockId loopExit = cfg.newIsolatedBlock();
fLoopExits.push(loopExit);
if (f.fTest) {
this->addExpression(cfg, &f.fTest, true);
// this isn't quite right; we should have an exit from here to the loop exit, and
// remove the exit from the loop body to the loop exit. Structuring it like this
// forces the optimizer to believe that the loop body is always executed at least
// once. While not strictly correct, this avoids incorrect "variable not assigned"
// errors on variables which are assigned within the loop. The correct solution to
// this is to analyze the loop to see whether or not at least one iteration is
// guaranteed to happen, but for the time being we take the easy way out.
}
cfg.newBlock();
this->addStatement(cfg, &f.fStatement);
cfg.addExit(cfg.fCurrent, next);
cfg.fCurrent = next;
if (f.fNext) {
this->addExpression(cfg, &f.fNext, true);
}
cfg.addExit(cfg.fCurrent, loopStart);
cfg.addExit(cfg.fCurrent, loopExit);
fLoopContinues.pop();
fLoopExits.pop();
cfg.fCurrent = loopExit;
break;
}
case Statement::kSwitch_Kind: {
SwitchStatement& ss = (SwitchStatement&) **s;
this->addExpression(cfg, &ss.fValue, true);
cfg.fBlocks[cfg.fCurrent].fNodes.push_back({ BasicBlock::Node::kStatement_Kind, false,
nullptr, s });
BlockId start = cfg.fCurrent;
BlockId switchExit = cfg.newIsolatedBlock();
fLoopExits.push(switchExit);
for (const auto& c : ss.fCases) {
cfg.newBlock();
cfg.addExit(start, cfg.fCurrent);
if (c->fValue) {
// technically this should go in the start block, but it doesn't actually matter
// because it must be constant. Not worth running two loops for.
this->addExpression(cfg, &c->fValue, true);
}
for (auto& caseStatement : c->fStatements) {
this->addStatement(cfg, &caseStatement);
}
}
cfg.addExit(cfg.fCurrent, switchExit);
// note that unlike GLSL, our grammar requires the default case to be last
if (0 == ss.fCases.size() || ss.fCases[ss.fCases.size() - 1]->fValue) {
// switch does not have a default clause, mark that it can skip straight to the end
cfg.addExit(start, switchExit);
}
fLoopExits.pop();
cfg.fCurrent = switchExit;
break;
}
case Statement::kNop_Kind:
break;
default:
printf("statement: %s\n", (*s)->description().c_str());
ABORT("unsupported statement kind");
}
}
CFG CFGGenerator::getCFG(FunctionDefinition& f) {
CFG result;
result.fStart = result.newBlock();
result.fCurrent = result.fStart;
this->addStatement(result, &f.fBody);
result.newBlock();
result.fExit = result.fCurrent;
return result;
}
} // namespace