diff options
| -rw-r--r-- | users/tazjin/rlox/examples/if.lox | 5 | ||||
| -rw-r--r-- | users/tazjin/rlox/src/bytecode/compiler.rs | 65 | ||||
| -rw-r--r-- | users/tazjin/rlox/src/bytecode/opcode.rs | 7 | ||||
| -rw-r--r-- | users/tazjin/rlox/src/bytecode/vm.rs | 23 |
4 files changed, 84 insertions, 16 deletions
diff --git a/users/tazjin/rlox/examples/if.lox b/users/tazjin/rlox/examples/if.lox new file mode 100644 index 0000000000..b59f00b201 --- /dev/null +++ b/users/tazjin/rlox/examples/if.lox @@ -0,0 +1,5 @@ +if (true) { + print "yes"; +} + +print "afterwards"; diff --git a/users/tazjin/rlox/src/bytecode/compiler.rs b/users/tazjin/rlox/src/bytecode/compiler.rs index 392fc9b72d..1b87e94a55 100644 --- a/users/tazjin/rlox/src/bytecode/compiler.rs +++ b/users/tazjin/rlox/src/bytecode/compiler.rs @@ -1,7 +1,7 @@ use super::chunk::Chunk; use super::errors::{Error, ErrorKind, LoxResult}; use super::interner::{InternedStr, Interner}; -use super::opcode::{CodeIdx, ConstantIdx, OpCode, StackIdx}; +use super::opcode::{CodeIdx, CodeOffset, ConstantIdx, OpCode, StackIdx}; use super::value::Value; use crate::scanner::{self, Token, TokenKind}; @@ -236,9 +236,13 @@ impl<T: Iterator<Item = Token>> Compiler<T> { fn define_variable(&mut self, var: Option<ConstantIdx>) -> LoxResult<()> { if self.locals.scope_depth == 0 { - self.emit_op(OpCode::OpDefineGlobal(var.expect("should be global"))); + self.emit_op(OpCode::OpDefineGlobal( + var.expect("should be global"), + )); } else { - self.locals.locals.last_mut() + self.locals + .locals + .last_mut() .expect("fatal: variable not yet added at definition") .depth = Depth::At(self.locals.scope_depth); } @@ -263,6 +267,8 @@ impl<T: Iterator<Item = Token>> Compiler<T> { fn statement(&mut self) -> LoxResult<()> { if self.match_token(&TokenKind::Print) { self.print_statement() + } else if self.match_token(&TokenKind::If) { + self.if_statement() } else if self.match_token(&TokenKind::LeftBrace) { self.begin_scope(); self.block()?; @@ -289,7 +295,9 @@ impl<T: Iterator<Item = Token>> Compiler<T> { self.locals.scope_depth -= 1; while self.locals.locals.len() > 0 - && self.locals.locals[self.locals.locals.len() - 1].depth.above(self.locals.scope_depth) + && self.locals.locals[self.locals.locals.len() - 1] + .depth + .above(self.locals.scope_depth) { self.emit_op(OpCode::OpPop); self.locals.locals.remove(self.locals.locals.len() - 1); @@ -319,6 +327,28 @@ impl<T: Iterator<Item = Token>> Compiler<T> { Ok(()) } + fn if_statement(&mut self) -> LoxResult<()> { + consume!( + self, + TokenKind::LeftParen, + ErrorKind::ExpectedToken("Expected '(' after 'if'") + ); + + self.expression()?; + + consume!( + self, + TokenKind::RightParen, + ErrorKind::ExpectedToken("Expected ')' after condition") + ); + + let then_jump = self.emit_op(OpCode::OpJumpPlaceholder(false)); + self.statement()?; + self.patch_jump(then_jump); + + Ok(()) + } + fn number(&mut self) -> LoxResult<()> { if let TokenKind::Number(num) = self.previous().kind { self.emit_constant(Value::Number(num), true); @@ -431,16 +461,12 @@ impl<T: Iterator<Item = Token>> Compiler<T> { self.expression()?; match local_idx { Some(idx) => self.emit_op(OpCode::OpSetLocal(idx)), - None => { - self.emit_op(OpCode::OpSetGlobal(ident.unwrap())) - } + None => self.emit_op(OpCode::OpSetGlobal(ident.unwrap())), }; } else { match local_idx { Some(idx) => self.emit_op(OpCode::OpGetLocal(idx)), - None => { - self.emit_op(OpCode::OpGetGlobal(ident.unwrap())) - } + None => self.emit_op(OpCode::OpGetGlobal(ident.unwrap())), }; } @@ -477,10 +503,7 @@ impl<T: Iterator<Item = Token>> Compiler<T> { Ok(()) } - fn identifier_str( - &mut self, - token: &Token, - ) -> LoxResult<InternedStr> { + fn identifier_str(&mut self, token: &Token) -> LoxResult<InternedStr> { let ident = match &token.kind { TokenKind::Identifier(ident) => ident.to_string(), _ => { @@ -594,6 +617,20 @@ impl<T: Iterator<Item = Token>> Compiler<T> { idx } + fn patch_jump(&mut self, idx: CodeIdx) { + let offset = CodeOffset(self.chunk.code.len() - idx.0 - 1); + + if let OpCode::OpJumpPlaceholder(false) = self.chunk.code[idx.0] { + self.chunk.code[idx.0] = OpCode::OpJumpIfFalse(offset); + return; + } + + panic!( + "attempted to patch unsupported op: {:?}", + self.chunk.code[idx.0] + ); + } + fn previous(&self) -> &Token { self.previous .as_ref() diff --git a/users/tazjin/rlox/src/bytecode/opcode.rs b/users/tazjin/rlox/src/bytecode/opcode.rs index 13e2f23939..accc6b3bac 100644 --- a/users/tazjin/rlox/src/bytecode/opcode.rs +++ b/users/tazjin/rlox/src/bytecode/opcode.rs @@ -7,6 +7,9 @@ pub struct StackIdx(pub usize); #[derive(Clone, Copy, Debug)] pub struct CodeIdx(pub usize); +#[derive(Clone, Copy, Debug)] +pub struct CodeOffset(pub usize); + #[derive(Debug)] pub enum OpCode { /// Push a constant onto the stack. @@ -45,4 +48,8 @@ pub enum OpCode { OpSetGlobal(ConstantIdx), OpGetLocal(StackIdx), OpSetLocal(StackIdx), + + // Control flow + OpJumpPlaceholder(bool), + OpJumpIfFalse(CodeOffset), } diff --git a/users/tazjin/rlox/src/bytecode/vm.rs b/users/tazjin/rlox/src/bytecode/vm.rs index bbdf70d8dc..e0db97abe5 100644 --- a/users/tazjin/rlox/src/bytecode/vm.rs +++ b/users/tazjin/rlox/src/bytecode/vm.rs @@ -201,8 +201,27 @@ impl VM { } OpCode::OpSetLocal(local_idx) => { - debug_assert!(self.stack.len() > local_idx.0, "stack is not currently large enough for local"); - self.stack[local_idx.0] = self.stack.last().unwrap().clone(); + debug_assert!( + self.stack.len() > local_idx.0, + "stack is not currently large enough for local" + ); + self.stack[local_idx.0] = + self.stack.last().unwrap().clone(); + } + + OpCode::OpJumpPlaceholder(_) => { + panic!("unpatched jump detected - this is a fatal compiler error!"); + } + + OpCode::OpJumpIfFalse(offset) => { + if self + .stack + .last() + .expect("condition should leave a value on the stack") + .is_falsey() + { + self.ip += offset.0; + } } } |