1 files changed, 48 insertions, 1 deletions

diff --git a/src/codegen.zig b/src/codegen.zig
index e52fb47..011d28a 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -529,6 +529,18 @@ const RegisterAllocator = struct {
         std.debug.assert(std.mem.indexOfScalar(Register, self.available.items, reg) == null);
         return self.available.appendAssumeCapacity(reg);
     }
+
+    fn allocateAux(self: *RegisterAllocator) !Register {
+        const reg = self.available.pop() orelse return error.OutOfRegisters;
+        return reg;
+    }
+
+    fn freeAux(self: *RegisterAllocator, reg: Register) void {
+        var it = self.allocated.valueIterator();
+        while (it.next()) |r| std.debug.assert(reg != r.*);
+        std.debug.assert(std.mem.indexOfScalar(Register, self.available.items, reg) == null);
+        return self.available.appendAssumeCapacity(reg);
+    }
 };
 
 const Context = struct {
@@ -597,6 +609,41 @@ const Context = struct {
         }
     }
 
+    fn genPrint(self: *Context, print: compile.Instr.Print) !void {
+        const arg = self.register_allocator.get(print.arg);
+
+        const quot = try self.register_allocator.allocateAux();
+        defer self.register_allocator.freeAux(quot);
+        const aux1 = try self.register_allocator.allocateAux();
+        defer self.register_allocator.freeAux(aux1);
+        const count = try self.register_allocator.allocateAux();
+        defer self.register_allocator.freeAux(count);
+
+        try self.maybeFreeSources(print.sources());
+
+        try self.emit(.addi(aux1, .zero, '\n'));
+        try self.emit(.addi(.sp, .sp, -1));
+        try self.emit(.sb(.sp, 0, aux1));
+        try self.emit(.addi(count, .zero, 1));
+
+        try self.emit(.addi(aux1, arg, 0));
+        try self.emit(.addi(quot, .zero, 10));
+        try self.emit(.divu(arg, aux1, quot));
+        try self.emit(.remu(aux1, aux1, quot));
+        try self.emit(.addi(aux1, aux1, '0'));
+        try self.emit(.addi(.sp, .sp, -1));
+        try self.emit(.sb(.sp, 0, aux1));
+        try self.emit(.addi(count, count, 1));
+        try self.emit(.bne(arg, .zero, -4 * 8));
+
+        try self.emit(.addi(.a7, .zero, 64)); // no = write
+        try self.emit(.addi(.a0, .zero, 1)); // fd = stdout
+        try self.emit(.addi(.a1, .sp, 0)); // buf = sp
+        try self.emit(.addi(.a2, count, 0)); // count = count
+        try self.emit(.ecall()); // syscall(no, fd, buf, count)
+        try self.emit(.add(.sp, .sp, count));
+    }
+
     fn codegenInstr(self: *Context, instr: compile.Instr) !void {
         switch (instr.type) {
             inline else => |ty| {
@@ -635,7 +682,7 @@ pub fn create_elf(allocator: Allocator, block: compile.Block) ![]u8 {
     try ctx.codegenBlock(block);
 
     try ctx.instructions.appendSlice(&[_]Instruction{
-        .addi(.a0, ctx.register_allocator.get(block.instrs[block.instrs.len - 1].dest()), 0),
+        .addi(.a0, .zero, 0),
         .addi(.a7, .zero, 93),
         .ecall(),
     });