Fix alignment when branching

codegen-luajit/src/backend/statement.rs

@@ -5,7 +5,7 @@ use std::{
 
 use parity_wasm::elements::ValueType;
 use wasm_ast::node::{
-	Backward, Br, BrTable, Call, CallIndirect, Forward, FuncData, If, SetGlobal, SetLocal,
+	Backward, Br, BrIf, BrTable, Call, CallIndirect, Forward, FuncData, If, SetGlobal, SetLocal,
 	SetTemporary, Statement, StoreAt, Terminator,
 };
 
@@ -13,66 +13,40 @@ use super::manager::{
 	write_ascending, write_condition, write_separated, write_variable, Driver, Manager,
 };
 
-fn write_br_at(up: usize, mng: &Manager, w: &mut dyn Write) -> Result<()> {
+impl Driver for Br {
-	let level = mng.label_list().iter().nth_back(up).unwrap();
+	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
+		let level = *mng.label_list().iter().nth_back(self.target).unwrap();
+
+		if !self.align.is_aligned() {
+			write_ascending("reg", self.align.new_range(), w)?;
+			write!(w, " = ")?;
+			write_ascending("reg", self.align.old_range(), w)?;
+			write!(w, " ")?;
+		}
 
 		write!(w, "goto continue_at_{level} ")
 	}
-
-impl Driver for Br {
-	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
-		write_br_at(self.target, mng, w)
-	}
-}
-
-fn condense_jump_table(list: &[u32]) -> Vec<(usize, usize, u32)> {
-	let mut result = Vec::new();
-	let mut index = 0;
-
-	while index < list.len() {
-		let start = index;
-
-		loop {
-			index += 1;
-
-			// if end of list or next value is not equal, break
-			if index == list.len() || list[index - 1] != list[index] {
-				break;
-			}
-		}
-
-		result.push((start, index - 1, list[start]));
-	}
-
-	result
 }
 
 impl Driver for BrTable {
 	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
-		let default = self.data.default.try_into().unwrap();
-
-		// Our condition should be pure so we probably don't need
-		// to emit it in this case.
-		if self.data.table.is_empty() {
-			return write_br_at(default, mng, w);
-		}
-
 		write!(w, "temp = ")?;
 		self.cond.write(mng, w)?;
 
-		for (start, end, dest) in condense_jump_table(&self.data.table) {
+		// Our condition should be pure so we probably don't need
-			if start == end {
+		// to emit it in this case.
-				write!(w, "if temp == {start} then ")?;
+		if self.data.is_empty() {
-			} else {
+			return self.default.write(mng, w);
-				write!(w, "if temp >= {start} and temp <= {end} then ")?;
 		}
 
-			write_br_at(dest.try_into().unwrap(), mng, w)?;
+		for (case, dest) in self.data.iter().enumerate() {
+			write!(w, "if temp == {case} then ")?;
+			dest.write(mng, w)?;
 			write!(w, "else")?;
 		}
 
 		write!(w, " ")?;
-		write_br_at(default, mng, w)?;
+		self.default.write(mng, w)?;
 		write!(w, "end ")
 	}
 }
@@ -127,6 +101,16 @@ impl Driver for Backward {
 	}
 }
 
+impl Driver for BrIf {
+	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
+		write!(w, "if ")?;
+		write_condition(&self.cond, mng, w)?;
+		write!(w, "then ")?;
+		self.target.write(mng, w)?;
+		write!(w, "end ")
+	}
+}
+
 impl Driver for If {
 	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
 		write!(w, "if ")?;
@@ -220,6 +204,7 @@ impl Driver for Statement {
 		match self {
 			Self::Forward(s) => s.write(mng, w),
 			Self::Backward(s) => s.write(mng, w),
+			Self::BrIf(s) => s.write(mng, w),
 			Self::If(s) => s.write(mng, w),
 			Self::Call(s) => s.write(mng, w),
 			Self::CallIndirect(s) => s.write(mng, w),

codegen-luau/src/backend/statement.rs

@@ -5,7 +5,7 @@ use std::{
 
 use parity_wasm::elements::ValueType;
 use wasm_ast::node::{
-	Backward, Br, BrTable, Call, CallIndirect, Forward, FuncData, If, SetGlobal, SetLocal,
+	Backward, Br, BrIf, BrTable, Call, CallIndirect, Forward, FuncData, If, SetGlobal, SetLocal,
 	SetTemporary, Statement, StoreAt, Terminator,
 };
 
@@ -13,17 +13,25 @@ use super::manager::{
 	write_ascending, write_condition, write_separated, write_variable, Driver, Label, Manager,
 };
 
-fn write_br_at(up: usize, mng: &Manager, w: &mut dyn Write) -> Result<()> {
+impl Driver for Br {
+	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
 		write!(w, "do ")?;
 
-	if up == 0 {
+		if !self.align.is_aligned() {
+			write_ascending("reg", self.align.new_range(), w)?;
+			write!(w, " = ")?;
+			write_ascending("reg", self.align.old_range(), w)?;
+			write!(w, " ")?;
+		}
+
+		if self.target == 0 {
 			if let Some(&Label::Backward) = mng.label_list().last() {
 				write!(w, "continue ")?;
 			} else {
 				write!(w, "break ")?;
 			}
 		} else {
-		let level = mng.label_list().len() - 1 - up;
+			let level = mng.label_list().len() - 1 - self.target;
 
 			write!(w, "desired = {level} ")?;
 			write!(w, "break ")?;
@@ -31,32 +39,27 @@ fn write_br_at(up: usize, mng: &Manager, w: &mut dyn Write) -> Result<()> {
 
 		write!(w, "end ")
 	}
-
-impl Driver for Br {
-	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
-		write_br_at(self.target, mng, w)
-	}
 }
 
 impl Driver for BrTable {
 	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
-		write!(w, "do ")?;
+		write!(w, "temp = ")?;
-		write!(w, "local temp = {{")?;
-
-		if !self.data.table.is_empty() {
-			write!(w, "[0] =")?;
-
-			for d in self.data.table.iter() {
-				write!(w, "{d}, ")?;
-			}
-		}
-
-		write!(w, "}} ")?;
-
-		write!(w, "desired = temp[")?;
 		self.cond.write(mng, w)?;
-		write!(w, "] or {} ", self.data.default)?;
+
-		write!(w, "break ")?;
+		// Our condition should be pure so we probably don't need
+		// to emit it in this case.
+		if self.data.is_empty() {
+			return self.default.write(mng, w);
+		}
+
+		for (case, dest) in self.data.iter().enumerate() {
+			write!(w, "if temp == {case} then ")?;
+			dest.write(mng, w)?;
+			write!(w, "else")?;
+		}
+
+		write!(w, " ")?;
+		self.default.write(mng, w)?;
 		write!(w, "end ")
 	}
 }
@@ -133,6 +136,16 @@ impl Driver for Backward {
 	}
 }
 
+impl Driver for BrIf {
+	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
+		write!(w, "if ")?;
+		write_condition(&self.cond, mng, w)?;
+		write!(w, "then ")?;
+		self.target.write(mng, w)?;
+		write!(w, "end ")
+	}
+}
+
 impl Driver for If {
 	fn write(&self, mng: &mut Manager, w: &mut dyn Write) -> Result<()> {
 		write!(w, "while true do ")?;
@@ -227,6 +240,7 @@ impl Driver for Statement {
 		match self {
 			Self::Forward(s) => s.write(mng, w),
 			Self::Backward(s) => s.write(mng, w),
+			Self::BrIf(s) => s.write(mng, w),
 			Self::If(s) => s.write(mng, w),
 			Self::Call(s) => s.write(mng, w),
 			Self::CallIndirect(s) => s.write(mng, w),

wasm-ast/src/builder.rs

@@ -4,10 +4,10 @@ use parity_wasm::elements::{
 };
 
 use crate::node::{
-	Backward, BinOp, BinOpType, Br, BrTable, Call, CallIndirect, CmpOp, CmpOpType, Expression,
+	Align, Backward, BinOp, BinOpType, Br, BrIf, BrTable, Call, CallIndirect, CmpOp, CmpOpType,
-	Forward, FuncData, GetGlobal, GetLocal, GetTemporary, If, LoadAt, LoadType, MemoryGrow,
+	Expression, Forward, FuncData, GetGlobal, GetLocal, GetTemporary, If, LoadAt, LoadType,
-	MemorySize, Select, SetGlobal, SetLocal, SetTemporary, Statement, StoreAt, StoreType,
+	MemoryGrow, MemorySize, Select, SetGlobal, SetLocal, SetTemporary, Statement, StoreAt,
-	Terminator, UnOp, UnOpType, Value,
+	StoreType, Terminator, UnOp, UnOpType, Value,
 };
 
 macro_rules! leak_with_predicate {
@@ -291,27 +291,21 @@ impl StatList {
 		}
 	}
 
-	// Return values from a block by leaking the stack and then
+	// Return the alignment necessary for this block to branch out to a
-	// adjusting the start if necessary.
+	// another given block
-	fn set_return_data(&mut self, par_previous: usize, par_result: usize) {
+	fn get_br_alignment(&self, par_start: usize, par_result: usize) -> Align {
+		let start = self.stack.len() + self.num_previous - par_result;
+
+		Align {
+			new: par_start,
+			old: start,
+			length: par_result,
+		}
+	}
+
+	fn set_terminator(&mut self, term: Terminator) {
 		self.leak_all();
-
+		self.last = Some(term);
-		// If the start of our copy and parent frame are the same our results
-		// are already in the right registers.
-		let start = self.num_previous + self.stack.len() - par_result;
-
-		if start == par_previous {
-			return;
-		}
-
-		for i in 0..par_result {
-			let data = Statement::SetTemporary(SetTemporary {
-				var: par_previous + i,
-				value: Expression::GetTemporary(GetTemporary { var: start + i }),
-			});
-
-			self.code.push(data);
-		}
 	}
 }
 
@@ -443,6 +437,25 @@ impl<'a> Builder<'a> {
 		}
 	}
 
+	fn get_relative_block(&self, index: usize) -> Option<&StatList> {
+		if index == 0 {
+			Some(&self.target)
+		} else {
+			self.pending.get(self.pending.len() - index)
+		}
+	}
+
+	fn get_br_terminator(&self, target: usize) -> Br {
+		let (par_start, par_result) = match self.get_relative_block(target) {
+			Some(v) => (v.num_previous, v.num_result),
+			None => (0, self.num_result),
+		};
+
+		let align = self.target.get_br_alignment(par_start, par_result);
+
+		Br { target, align }
+	}
+
 	fn add_call(&mut self, func: usize) {
 		let arity = self.type_info.rel_arity_of(func);
 		let param_list = self.target.pop_len(arity.num_param);
@@ -483,32 +496,6 @@ impl<'a> Builder<'a> {
 		self.target.code.push(data);
 	}
 
-	fn get_relative_block(&self, index: usize) -> Option<&StatList> {
-		if index == 0 {
-			Some(&self.target)
-		} else {
-			self.pending.get(self.pending.len() - index)
-		}
-	}
-
-	fn set_return_data(&mut self, target: usize) {
-		let (par_previous, par_result) = match self.get_relative_block(target) {
-			Some(v) => (v.num_previous, v.num_result),
-			None => (0, self.num_result),
-		};
-
-		self.target.set_return_data(par_previous, par_result);
-	}
-
-	fn set_br_to_block(&mut self, target: usize) {
-		self.nested_unreachable += 1;
-
-		let data = Terminator::Br(Br { target });
-
-		self.set_return_data(target);
-		self.target.last = Some(data);
-	}
-
 	#[cold]
 	fn drop_unreachable(&mut self, inst: &Instruction) {
 		match inst {
@@ -543,8 +530,7 @@ impl<'a> Builder<'a> {
 			Inst::Unreachable => {
 				self.nested_unreachable += 1;
 
-				self.target.leak_all();
+				self.target.set_terminator(Terminator::Unreachable);
-				self.target.last = Some(Terminator::Unreachable);
 			}
 			Inst::Nop => {}
 			Inst::Block(typ) => {
@@ -567,48 +553,55 @@ impl<'a> Builder<'a> {
 				self.start_block(typ, stat);
 			}
 			Inst::Else => {
-				self.set_return_data(0);
+				self.target.leak_all();
 				self.start_else();
 			}
 			Inst::End => {
-				self.set_return_data(0);
+				self.target.leak_all();
 				self.end_block();
 			}
 			Inst::Br(v) => {
 				let target = v.try_into().unwrap();
+				let term = Terminator::Br(self.get_br_terminator(target));
 
-				self.set_br_to_block(target);
+				self.target.set_terminator(term);
+				self.nested_unreachable += 1;
 			}
 			Inst::BrIf(v) => {
-				let target: usize = v.try_into().unwrap();
+				let data = Statement::BrIf(BrIf {
-				let stat = Statement::If(If {
 					cond: self.target.pop_required(),
-					truthy: Forward::default(),
+					target: self.get_br_terminator(v.try_into().unwrap()),
-					falsey: None,
 				});
 
-				self.start_block(BlockType::NoResult, stat);
+				self.target.leak_all();
-				self.set_br_to_block(target + 1);
+				self.target.code.push(data);
-				self.end_block();
-
-				self.nested_unreachable -= 1;
 			}
 			Inst::BrTable(ref v) => {
-				self.nested_unreachable += 1;
+				let cond = self.target.pop_required();
+				let data = v
+					.table
+					.iter()
+					.copied()
+					.map(|v| self.get_br_terminator(v.try_into().unwrap()))
+					.collect();
 
-				let default = v.default.try_into().unwrap();
+				let default = self.get_br_terminator(v.default.try_into().unwrap());
-				let data = Terminator::BrTable(BrTable {
+
-					cond: self.target.pop_required(),
+				let term = Terminator::BrTable(BrTable {
-					data: *v.clone(),
+					cond,
+					data,
+					default,
 				});
 
-				self.set_return_data(default);
+				self.target.set_terminator(term);
-				self.target.last = Some(data);
+				self.nested_unreachable += 1;
 			}
 			Inst::Return => {
 				let target = self.pending.len();
+				let term = Terminator::Br(self.get_br_terminator(target));
 
-				self.set_br_to_block(target);
+				self.target.set_terminator(term);
+				self.nested_unreachable += 1;
 			}
 			Inst::Call(i) => {
 				self.add_call(i.try_into().unwrap());
@@ -744,7 +737,7 @@ impl<'a> Builder<'a> {
 		}
 
 		if self.nested_unreachable == 0 {
-			self.set_return_data(0);
+			self.target.leak_all();
 		}
 
 		std::mem::take(&mut self.target)

wasm-ast/src/node.rs

@@ -1,6 +1,6 @@
 use std::ops::Range;
 
-use parity_wasm::elements::{BrTableData, Instruction, Local, SignExtInstruction};
+use parity_wasm::elements::{Instruction, Local, SignExtInstruction};
 
 #[allow(non_camel_case_types)]
 #[derive(Clone, Copy)]
@@ -660,13 +660,38 @@ impl Expression {
 	}
 }
 
+pub struct Align {
+	pub new: usize,
+	pub old: usize,
+	pub length: usize,
+}
+
+impl Align {
+	#[must_use]
+	pub fn is_aligned(&self) -> bool {
+		self.length == 0 || self.new == self.old
+	}
+
+	#[must_use]
+	pub fn new_range(&self) -> Range<usize> {
+		self.new..self.new + self.length
+	}
+
+	#[must_use]
+	pub fn old_range(&self) -> Range<usize> {
+		self.old..self.old + self.length
+	}
+}
+
 pub struct Br {
 	pub target: usize,
+	pub align: Align,
 }
 
 pub struct BrTable {
 	pub cond: Expression,
-	pub data: BrTableData,
+	pub data: Vec<Br>,
+	pub default: Br,
 }
 
 pub enum Terminator {
@@ -687,6 +712,11 @@ pub struct Backward {
 	pub last: Option<Terminator>,
 }
 
+pub struct BrIf {
+	pub cond: Expression,
+	pub target: Br,
+}
+
 pub struct If {
 	pub cond: Expression,
 	pub truthy: Forward,
@@ -731,6 +761,7 @@ pub struct StoreAt {
 pub enum Statement {
 	Forward(Forward),
 	Backward(Backward),
+	BrIf(BrIf),
 	If(If),
 	Call(Call),
 	CallIndirect(CallIndirect),

wasm-ast/src/visit.rs

@@ -1,5 +1,5 @@
 use crate::node::{
-	Backward, BinOp, Br, BrTable, Call, CallIndirect, CmpOp, Expression, Forward, FuncData,
+	Backward, BinOp, Br, BrIf, BrTable, Call, CallIndirect, CmpOp, Expression, Forward, FuncData,
 	GetGlobal, GetLocal, GetTemporary, If, LoadAt, MemoryGrow, MemorySize, Select, SetGlobal,
 	SetLocal, SetTemporary, Statement, StoreAt, Terminator, UnOp, Value,
 };
@@ -41,6 +41,8 @@ pub trait Visitor {
 
 	fn visit_backward(&mut self, _: &Backward) {}
 
+	fn visit_br_if(&mut self, _: &BrIf) {}
+
 	fn visit_if(&mut self, _: &If) {}
 
 	fn visit_call(&mut self, _: &Call) {}
@@ -218,6 +220,14 @@ impl<T: Visitor> Driver<T> for Backward {
 	}
 }
 
+impl<T: Visitor> Driver<T> for BrIf {
+	fn accept(&self, visitor: &mut T) {
+		self.cond.accept(visitor);
+
+		visitor.visit_br_if(self);
+	}
+}
+
 impl<T: Visitor> Driver<T> for If {
 	fn accept(&self, visitor: &mut T) {
 		self.cond.accept(visitor);
@@ -291,6 +301,7 @@ impl<T: Visitor> Driver<T> for Statement {
 		match self {
 			Self::Forward(v) => v.accept(visitor),
 			Self::Backward(v) => v.accept(visitor),
+			Self::BrIf(v) => v.accept(visitor),
 			Self::If(v) => v.accept(visitor),
 			Self::Call(v) => v.accept(visitor),
 			Self::CallIndirect(v) => v.accept(visitor),