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pattern-gen: introduce behavior AST scaffolding for frontend/backend split #2

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90 changes: 75 additions & 15 deletions llvm/tools/pattern-gen/lib/Parser.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -93,8 +93,10 @@ static void pop_var_scope() {
scopeDepth--;
}

struct BehaviorStatement;

void ParseScope(TokenStream &ts, llvm::Function *func,
llvm::IRBuilder<> &build);
llvm::IRBuilder<> &build, BehaviorStatement *ast = nullptr);
Value ParseExpression(TokenStream &ts, llvm::Function *func,
llvm::IRBuilder<> &build, int minPrec = 0);

Expand Down Expand Up @@ -979,6 +981,49 @@ struct VarDef {
bool sgn;
};

struct BehaviorExpression {
enum Kind {
Generic,
Assignment,
Index,
} kind = Generic;
};

struct BehaviorStatement {
enum Kind {
Scope,
If,
While,
For,
Declaration,
Expr,
} kind;
llvm::SmallVector<BehaviorStatement, 4> children;
llvm::SmallVector<BehaviorExpression, 4> expressions;
};

static BehaviorExpression classify_expression(TokenStream &ts,
llvm::Function *func,
llvm::IRBuilder<> &build) {
// Frontend placeholder classification: we still use the legacy expression
// backend today, but behavior parsing now has an explicit expression model
// that can be evolved independently.
BehaviorExpression expr;
size_t start = ts.i;
Value v = ParseExpression(ts, func, build);
size_t end = ts.i;
(void)v;

auto slice = ts.src.substr(start, end - start);
if (slice.find('[') != std::string::npos)
expr.kind = BehaviorExpression::Index;
if (slice.find("=") != std::string::npos &&
slice.find("==") == std::string::npos)
expr.kind = BehaviorExpression::Assignment;

return expr;
}

VarDef ParseDefinition(TokenStream &ts) {
bool sgn = pop_cur_if(ts, SignedKeyword);
if (!sgn)
Expand Down Expand Up @@ -1022,7 +1067,9 @@ VarDef ParseDefinition(TokenStream &ts) {
}

void ParseDeclaration(TokenStream &ts, llvm::Function *func,
llvm::IRBuilder<> &build) {
llvm::IRBuilder<> &build, BehaviorStatement *ast = nullptr) {
if (ast)
ast->kind = BehaviorStatement::Declaration;
auto &ctx = func->getContext();

auto [ident, identIdx, bitSize, sgn] = ParseDefinition(ts);
Expand Down Expand Up @@ -1062,11 +1109,13 @@ void ParseDeclaration(TokenStream &ts, llvm::Function *func,
}

void ParseStatement(TokenStream &ts, llvm::Function *func,
llvm::IRBuilder<> &build) {
llvm::IRBuilder<> &build, BehaviorStatement *ast) {
auto &ctx = func->getContext();

switch (ts.Peek().type) {
case IfKeyword: {
if (ast)
ast->kind = BehaviorStatement::If;
ts.Pop();
pop_cur(ts, RBrOpen);
Value cond = ParseExpression(ts, func, build);
Expand All @@ -1079,13 +1128,13 @@ void ParseStatement(TokenStream &ts, llvm::Function *func,
build.CreateCondBr(condBool, bbTrue, bbFalse);

build.SetInsertPoint(bbTrue);
ParseStatement(ts, func, build);
ParseStatement(ts, func, build, nullptr);

if (pop_cur_if(ts, ElseKeyword)) {
llvm::BasicBlock *bbCont = llvm::BasicBlock::Create(ctx, "", func);
build.CreateBr(bbCont);
build.SetInsertPoint(bbFalse);
ParseStatement(ts, func, build);
ParseStatement(ts, func, build, nullptr);
build.CreateBr(bbCont);
build.SetInsertPoint(bbCont);
} else {
Expand All @@ -1096,18 +1145,22 @@ void ParseStatement(TokenStream &ts, llvm::Function *func,
}
case WhileKeyword:
case ForKeyword: {
bool isFor = ts.Peek().type == ForKeyword;
if (ast)
ast->kind = isFor ? BehaviorStatement::For : BehaviorStatement::While;

llvm::BasicBlock *bbHdr = llvm::BasicBlock::Create(ctx, "loop_hdr", func);
llvm::BasicBlock *bbBody = llvm::BasicBlock::Create(ctx, "loop_body", func);
llvm::BasicBlock *bbBreak =
llvm::BasicBlock::Create(ctx, "loop_break", func);
llvm::BasicBlock *bbInc = nullptr;

bool isFor = ts.Pop().type == ForKeyword;
ts.Pop();
pop_cur(ts, RBrOpen);
if (isFor) {
create_var_scope();
if (!pop_cur_if(ts, Semicolon))
ParseDeclaration(ts, func, build);
ParseDeclaration(ts, func, build, nullptr);
}

build.CreateBr(bbHdr);
Expand All @@ -1119,7 +1172,7 @@ void ParseStatement(TokenStream &ts, llvm::Function *func,
pop_cur(ts, Semicolon);
build.SetInsertPoint(bbInc);
if (!pop_cur_if(ts, Semicolon))
ParseExpression(ts, func, build);
classify_expression(ts, func, build);
build.CreateBr(bbHdr);
build.SetInsertPoint(bbHdr);
}
Expand All @@ -1130,7 +1183,7 @@ void ParseStatement(TokenStream &ts, llvm::Function *func,
build.CreateCondBr(condBool, bbBreak, bbBody);
build.SetInsertPoint(bbBody);

ParseStatement(ts, func, build);
ParseStatement(ts, func, build, nullptr);

build.CreateBr(isFor ? bbInc : bbHdr);
build.SetInsertPoint(bbBreak);
Expand All @@ -1141,27 +1194,33 @@ void ParseStatement(TokenStream &ts, llvm::Function *func,
}
case UnsignedKeyword:
case SignedKeyword: {
ParseDeclaration(ts, func, build);
ParseDeclaration(ts, func, build, ast);
break;
}
case CBrOpen:
ParseScope(ts, func, build);
ParseScope(ts, func, build, ast);
break;
default: {
ParseExpression(ts, func, build);
if (ast)
ast->kind = BehaviorStatement::Expr;
auto expr = classify_expression(ts, func, build);
if (ast)
ast->expressions.push_back(expr);
pop_cur(ts, Semicolon);
break;
}
}
}

void ParseScope(TokenStream &ts, llvm::Function *func,
llvm::IRBuilder<> &build) {
llvm::IRBuilder<> &build, BehaviorStatement *ast) {
if (ast)
ast->kind = BehaviorStatement::Scope;
pop_cur(ts, CBrOpen);
create_var_scope();

while (ts.Peek().type != CBrClose)
ParseStatement(ts, func, build);
ParseStatement(ts, func, build, nullptr);

pop_var_scope();
pop_cur(ts, CBrClose);
Expand Down Expand Up @@ -1430,7 +1489,8 @@ void ParseBehaviour(TokenStream &ts, CDSLInstr &instr, llvm::Module *mod,
{cond});
}

ParseStatement(ts, func, build);
BehaviorStatement behaviorAST{BehaviorStatement::Expr};
ParseStatement(ts, func, build, &behaviorAST);
build.CreateRetVoid();
}

Expand Down