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const std = @import("std");
const Allocator = std.mem.Allocator;
const root = @import("root");
const Token = root.Lexer.Token;
const Expr = root.Expr;
const Location = root.Lexer.Location;
pub const VReg = enum(u32) { _ };
pub const Instr = struct {
loc: Location,
type: Type,
pub const Type = union(enum) {
constant: Constant,
bin_op: BinOp,
print: Print,
};
pub const Constant = struct {
dest: VReg,
value: u64,
pub fn sources(_: Constant) Sources {
return Sources.init(0) catch unreachable;
}
};
pub const BinOp = struct {
dest: VReg,
lhs: VReg,
rhs: VReg,
op: Op,
const Op = enum {
add,
sub,
};
pub fn sources(self: BinOp) Sources {
return Sources.fromSlice(&.{ self.lhs, self.rhs }) catch unreachable;
}
};
pub const Print = struct {
arg: VReg,
pub fn sources(self: Print) Sources {
return Sources.fromSlice(&.{self.arg}) catch unreachable;
}
};
pub fn sources(self: Instr) Sources {
return switch (self.type) {
inline else => |instr| instr.sources(),
};
}
pub fn dest(self: *const Instr) ?VReg {
return switch (self.type) {
inline .constant, .bin_op => |s| s.dest,
inline .print => null,
};
}
pub const Sources = std.BoundedArray(VReg, 2);
};
pub const Block = struct {
// arguments: []Reg,
instrs: []Instr,
vreg_last_use: std.AutoHashMap(VReg, usize),
fn init(allocator: Allocator, instrs: []Instr) !Block {
var vreg_last_use: std.AutoHashMap(VReg, usize) = .init(allocator);
for (0.., instrs) |i, instr| {
for (instr.sources().slice()) |src|
try vreg_last_use.put(src, i);
}
return .{
.instrs = instrs,
.vreg_last_use = vreg_last_use,
};
}
};
pub fn compile(allocator: Allocator, source: []const u8, expr: *const Expr) !Block {
const instrs: std.ArrayListUnmanaged(Instr) = try .initCapacity(allocator, 0);
var ctx: CompileContext = .{
.allocator = allocator,
.source = source,
.register_counter = 0,
.instrs = instrs,
};
_ = try ctx.compileExpr(expr);
return .init(allocator, ctx.instrs.items);
}
const CompileContext = struct {
allocator: Allocator,
source: []const u8,
register_counter: u32,
instrs: std.ArrayListUnmanaged(Instr),
const Self = @This();
fn addInstr(self: *Self, instr: Instr) !void {
try self.instrs.append(self.allocator, instr);
}
fn compileExpr(self: *Self, expr: *const Expr) !VReg {
const dest = self.register();
switch (expr.type) {
.integer_literal => try addInstr(self, .{
.loc = expr.loc,
.type = .{ .constant = .{ .dest = dest, .value = expr.loc.getInt(self.source) } },
}),
.bin_op => |binop| {
const lhs = try self.compileExpr(binop.lhs);
const rhs = try self.compileExpr(binop.rhs);
try addInstr(self, .{
.loc = expr.loc,
.type = .{
.bin_op = .{
.dest = dest,
.lhs = lhs,
.rhs = rhs,
.op = switch (binop.op) {
.plus => .add,
.minus => .sub,
},
},
},
});
},
.call => |call| {
if (call.proc.type == .identifier and
std.mem.eql(u8, call.proc.loc.getIdent(self.source), "print"))
{
const arg = try self.compileExpr(call.arg);
try self.addInstr(.{
.loc = expr.loc,
.type = .{ .print = .{ .arg = arg } },
});
// BUG: we're returning a bogus virtual register that we didn't write to
} else {
return error.CantCallAnythingButPrint;
}
},
.identifier => return error.CantCompileIdentifierExpr,
.invalid => return error.CantCompileInvalidExpr,
}
return dest;
}
fn register(self: *Self) VReg {
const reg: VReg = @enumFromInt(self.register_counter);
self.register_counter += 1;
return reg;
}
};
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