diff --git a/tools/cc.py b/tools/cc.py
index 1d2b4c3..989344c 100644
--- a/tools/cc.py
+++ b/tools/cc.py
@@ -4,6 +4,7 @@ import collections
 import contextlib
 from dataclasses import dataclass
 import importlib
+import inspect
 import io
 import re
 import struct
@@ -34,6 +35,9 @@ class Variable:
     def __repr__(self):
         return f'<Var: {self.type} {self.name}>'
 
+    def __str__(self):
+        return self.name
+
     @classmethod
     def from_def(cls, tree):
         type = tree.children[0]
@@ -76,21 +80,42 @@ class Variable:
         print(tree)
 
 
+def allregs():
+    return (f'r{i}' for i in range(12))
+
+
 class RegBank:
     def __init__(self, logger=None):
         self.reset()
         self.log = logger or print
 
     def reset(self):
-        self.available = [f'r{i}' for i in range(12)]
+        self.available = list(allregs())
         self.vars = {}
         self.varregs = {}
         self.cleanup = collections.defaultdict(list)
+        self.taken = {}
 
-    def take(self, reg=None):
+    def __str__(self):
+        return f'regs(avail={self.available}, vars={self.vars})'
+
+    def take(self, reg=None, orwhatever=False):
+        out = self._take(reg=reg, orwhatever=orwhatever)
+        self.taken[out] = inspect.stack()[1]
+        return out
+
+    def _take(self, reg=None, orwhatever=False):
         if reg is not None:
             if reg not in self.available:
-                self.evict(self.var(reg))
+                if reg in self.varregs:
+                    self.evict(self.var(reg))
+                elif orwhatever:
+                    return self._take()
+                else:
+                    raise RuntimeError(
+                            f'trying to overtake {reg}, '
+                            f'varregs: {self.varregs}, vars: {self.vars}, '
+                            f'taken in {self.taken[reg]}')
             if reg in self.available:
                 self.available.remove(reg)
             return reg
@@ -102,6 +127,7 @@ class RegBank:
         return self.available.pop(0)
 
     def give(self, reg):
+        assert reg is not None
         if reg in self.varregs:
             # Need to call evict() with the var to free it.
             return
@@ -109,11 +135,13 @@ class RegBank:
 
     def loaded(self, var, reg, cleanup=None):
         """Tells the regbank some variable was loaded into the given register."""
+        assert reg is not None
+        assert var is not None
         self.vars[var] = reg
         self.varregs[reg] = var
         self.take(reg)
         if cleanup is not None:
-            self.log(f'recording cleanup for {reg}({var.name})')
+            self.log(f'recording cleanup for {reg}({var})')
             self.cleanup[reg].append(cleanup)
 
     def stored(self, var):
@@ -136,6 +164,7 @@ class RegBank:
 
     def assign(self, var, reg, cleanup=None):
         """Assign a previously-used register to a variable."""
+        assert reg is not None
         if var in self.vars:
             self.stored(var)
         if reg in self.varregs:
@@ -150,21 +179,25 @@ class RegBank:
     def var(self, reg):
         return self.varregs.get(reg, None)
 
+    def evict_all(self):
+        for var in list(self.vars):
+            self.evict(var)
+
     def evict(self, var):
         """Runs var callbacks & frees the register."""
+        assert var in self.vars, f'trying to evict {var}'
+        self.log(f'evicting {var}')
         if var not in self.vars:
             return
         reg = self.vars[var]
-        for cb in self.cleanup.pop(var, []):
+        for cb in self.cleanup.pop(reg, []):
             cb(reg)
         self.stored(var)
 
-    def flush_all(self):
-        for reg in list(self.cleanup):
-            self.log(f'flushing {reg}({self.varregs[reg].name})')
-            for cb in self.cleanup.pop(reg):
-                cb(reg)
-        self.reset()
+    def drop_temps(self):
+        for reg in allregs():
+            if reg not in self.available and reg not in self.varregs:
+                self.give(reg)
 
     def swapped(self, reg0, reg1):
         var0 = self.varregs.get(reg0, None)
@@ -192,6 +225,7 @@ class RegBank:
         self.reset()
         vardict, cleanup = snap
         for var, reg in vardict.items():
+            assert reg is not None, f'bad snapshot: {snap}'
             self.loaded(var, reg)
             self.cleanup[reg] = cleanup.get(reg, [])
 
@@ -225,6 +259,7 @@ class Function:
         self.params = [Variable(*x.children) for x in fun_prot.children[2:]]
         self.ret = None
         self.nextstack = 0
+        self.topstack = 0
         self.statements = []
         self.regs = RegBank(logger=self.log)
         self.deferred_ops = []
@@ -236,13 +271,24 @@ class Function:
 
     @property
     def stack_usage(self):
-        return self.nextstack + 2
+        top_usage = max(self.topstack, self.nextstack)
+        if self.fun_calls > 0:
+            return top_usage + 2
+        return top_usage
 
     def get_stack(self, size=2):
         stk = self.nextstack
         self.nextstack += size
         return stk
 
+    @contextlib.contextmanager
+    def tempstack(self):
+        stk = self.nextstack
+        yield
+        if self.nextstack > self.topstack:
+            self.topstack = self.nextstack
+        self.nextstack = stk
+
     def param_dict(self):
         return {p.name: p for p in self.params}
 
@@ -250,14 +296,12 @@ class Function:
         return repr(self.spec)
 
     def synth(self):
+        ops = []
         if self.fun_calls > 0:
-            preamble = [f'store lr, [sp, -2]',
-                        f'set r4, {self.stack_usage}',
-                        f'sub sp, sp, r4']
-        else:
-            preamble = []
-
-        ops = preamble
+            ops += [f'store lr, [sp, -2]']
+        if self.stack_usage > 0:
+            ops += [f'set r4, {self.stack_usage}',
+                    f'sub sp, sp, r4']
         for op in self.ops:
             ops += op()
         indented = [f' {x}' if x[-1] == ':' else f'  {x}' for x in ops]
@@ -524,17 +568,22 @@ class ReturnReg(AsmOp):
         (self.ret_reg,) = ops
 
     def synth(self, scratches):
-        if self.fun.fun_calls == 0:
-            return [f'or r0, {self.ret_reg}, {self.ret_reg}',
-                    f'or pc, lr, lr']
-        sc0 = scratches[0]
+        ops = []
         stack_usage = self.fun.stack_usage
-        ret = self.ret_reg
-        assert stack_usage < 255
-        return [f'set {sc0}, {stack_usage}',
-                f'add sp, sp, {sc0}',
-                f'or r0, {ret}, {ret}',
-                f'load pc, [sp, -2]  // return']
+        (sc0,) = scratches
+        if stack_usage > 0:
+            ops += [f'set {sc0}, {stack_usage}',
+                    f'add sp, sp, {sc0}']
+        if self.fun.ret is not None:
+            ret = self.ret_reg
+            ops += [f'or r0, {ret}, {ret}']
+
+        if self.fun.fun_calls == 0:
+            ops += [f'or pc, lr, lr']
+        else:
+            ops += [f'load pc, [sp, -2]  // return']
+
+        return ops
 
 
 class Load(AsmOp):
@@ -574,6 +623,29 @@ class Load(AsmOp):
                     f'nop  // in case we load a far global',
                     f'load {reg}, [{reg}]']  # unsure if we need a cast here
 
+
+class Push(AsmOp):
+    def __init__(self, reg, stackaddr):
+        self.reg = reg
+        self.stackaddr = stackaddr
+
+    def synth(self, scratches):
+        return [f'store {self.reg}, [sp, {self.stackaddr}]']
+
+
+class Pop(AsmOp):
+    def __init__(self, reg, stackaddr):
+        self.reg = reg
+        self.stackaddr = stackaddr
+
+    @property
+    def out(self):
+        return self.reg
+
+    def synth(self, scratches):
+        return [f'load {self.reg}, [sp, {self.stackaddr}]']
+
+
 class Store(AsmOp):
     scratch_need = 1
 
@@ -581,10 +653,6 @@ class Store(AsmOp):
         self.fun = fun
         self.src, self.var = ops
 
-    @property
-    def out(self):
-        return None
-
     def synth(self, scratches):
         (sc,) = scratches
         reg = self.src
@@ -820,11 +888,11 @@ class CcInterp(lark.visitors.Interpreter):
             self._log(f'{op.__class__.__name__}')
             self.cur_fun.ops.append(lambda: op.synth(scratches))
 
-    def _load(self, ident):
+    def _load(self, ident, reg=None):
         s = self._lookup_symbol(ident)
         assert s is not None, f'unknown identifier {ident}'
         if isinstance(s, FunctionSpec) or ident in self.global_scope.symbols:
-            reg = self._get_reg()
+            reg = reg or self._get_reg()
             return SetAddr(self.cur_fun, [reg, ident])
         else:
             if s.type.volatile:
@@ -845,7 +913,8 @@ class CcInterp(lark.visitors.Interpreter):
         # If it's volatile, we need to flush it.
         def delayed_load():
             self._log(f'delay-loading {tree.children[0]}')
-            op = self._load(tree.children[0])
+            reg = getattr(tree, 'request_out', None)
+            op = self._load(tree.children[0], reg=reg)
             self._synth(op)
             return op.out
 
@@ -868,10 +937,17 @@ class CcInterp(lark.visitors.Interpreter):
             tok = self._make_string(imm)
             tree.children = [tok]
             return self.identifier(tree)
-        reg = self._get_reg()
-        assert self.cur_fun is not None
-        tree.op = Set16Imm(self.cur_fun, [reg, imm])
-        self._synth(tree.op)
+        def delayed():
+            if hasattr(tree, 'request_out'):
+                reg = self.cur_fun.regs.take(reg=tree.request_out, orwhatever=True)
+            else:
+                reg = self.cur_fun.regs.take()
+                assert reg is not None, f'weird: {self.cur_fun.regs}'
+            op = Set16Imm(self.cur_fun, [reg, imm])
+            self._synth(op)
+            return op.out
+
+        tree.op = Delayed(delayed)
         tree.type = litt_type(tree.children[0])
 
     def _assign(self, left, right):
@@ -884,6 +960,7 @@ class CcInterp(lark.visitors.Interpreter):
     def assignment(self, tree):
         self.visit_children(tree)
         val = tree.children[1].op.out
+        assert val is not None, f'no output!!! {tree.pretty()}'
 
         # left hand side is an lvalue, retrieve it
         var = tree.children[0].var
@@ -916,7 +993,7 @@ class CcInterp(lark.visitors.Interpreter):
 
         for i, r in enumerate(dst):
             if r not in src:
-                self.cur_fun.regs.take(r)  # precious!
+                #self.cur_fun.regs.take(r)  # precious!
                 self._synth(Move(r, src[i]))
             else:
                 swap(r, src[i])
@@ -924,46 +1001,92 @@ class CcInterp(lark.visitors.Interpreter):
 
     def _prep_fun_call(self, fn_reg, params):
         """Move all params to r0-rn."""
-        target_regs = [f'r{i}' for i in range(len(params))]
-        new_fn = fn_reg
-        while new_fn in target_regs or new_fn in params:
-            new_fn = self.cur_fun.regs.take()
-        if new_fn != fn_reg:
-            self._synth(Move(new_fn, fn_reg))
-            fn_reg = new_fn
-        self._reg_shuffle(params, target_regs)
-        return fn_reg
+        target_regs = [f'r{i}' for i in range(len(params) + 1)]
+        self._reg_shuffle(params + [fn_reg], target_regs)
+        return target_regs[-1]
+
+    @contextlib.contextmanager
+    def _push(self, dontpush=()):
+        pushed = []
+        self.cur_fun.regs.evict_all()
+        with self.cur_fun.tempstack():
+            for reg in allregs():
+                if reg not in self.cur_fun.regs.available and reg not in dontpush:
+                    self._log(f'reg in use: {reg}')
+                    stk = self.cur_fun.get_stack()
+                    pushed.append((reg, stk))
+                    self._synth(Push(reg, stk))
+                    self.cur_fun.regs.give(reg)
+            yield pushed
 
     def fun_call(self, tree):
         self.cur_fun.fun_calls += 1
-        self.visit_children(tree)
-        fn_reg = tree.children[0].op.out
         if len(tree.children) == 1:
-            param_regs = []
+            param_children = []
         elif tree.children[1].data == 'comma_expr':
-            param_regs = [c.op.out for c in tree.children[1].children]
+            param_children = tree.children[1].children
         else:
-            param_regs = [tree.children[1].op.out]
-        self._log(f'calling {tree.children[0].children[0]}({param_regs})')
-        self.cur_fun.regs.flush_all()
-        for i in range(len(param_regs)):
-            self.cur_fun.regs.take(f'r{i}')
-        fn_reg = self._prep_fun_call(fn_reg, param_regs)
-        self.cur_fun.regs.take(fn_reg)
-        tree.op = FnCall(self.cur_fun, [fn_reg, param_regs])
-        self._synth(tree.op)
-        self.cur_fun.regs.reset()
-        self.cur_fun.regs.take('r0')
+            param_children = [tree.children[1]]
+
+
+        if True:
+            # pre-allocate output registers
+            for i, child in enumerate(param_children):
+                self._log(f'requesting r{i} for {child}')
+                child.request_out = f'r{i}'
+            self._log(f'requesting r{len(param_children)} for {tree.children[0]}')
+            tree.children[0].request_out = f'r{len(param_children)}'
+            self.visit_children(tree)
+            fn_reg = tree.children[0].op.out
+            param_regs = [c.op.out for c in param_children]
+            self._log(f'calling {tree.children[0].children[0]}({param_regs})')
+
+        with self._push(dontpush=param_regs + [fn_reg]) as pushed:
+
+            self._flush_deferred()  # side effects
+            fn_reg = self._prep_fun_call(fn_reg, param_regs)
+            self.cur_fun.regs.reset()
+            self.cur_fun.regs.take(fn_reg)
+            for reg in (f'r{i}' for i in range(len(param_regs))):
+                self.cur_fun.regs.take(reg)
+
+            tree.op = FnCall(self.cur_fun, [fn_reg, param_regs])
+            self._synth(tree.op)
+
+            self.cur_fun.regs.reset()
+
+            pops = []
+            for reg, stk in pushed:
+                self.cur_fun.regs.take(reg)
+                pops.append(Pop(reg, stk))
+
+        ret = 'r0'
+        if hasattr(tree, 'request_out'):
+            ret = tree.request_out
+            self._synth(Move(ret, 'r0'))
+
+        nret = self.cur_fun.regs.take(ret, orwhatever=True)
+        if nret != ret:
+            self._synth(Move(nret, ret))
+        tree.op = type('blah', (), {'out': nret})
+
+        for op in pops:
+            self._synth(op)
+
         tree.type = return_type(tree.children[0].type)
 
-    def statement(self, tree):
-        self.visit_children(tree)
+    def _flush_deferred(self):
         if self.cur_fun.deferred_ops:
             self._log(f'deferred logic: {len(self.cur_fun.deferred_ops)}')
         for op in self.cur_fun.deferred_ops:
             self._synth(op)
         self.cur_fun.deferred_ops = []
 
+    def statement(self, tree):
+        self.visit_children(tree)
+        self._flush_deferred()
+        self.cur_fun.regs.drop_temps()
+
     iter_expression = statement
 
     def if_stat(self, tree):
@@ -978,6 +1101,7 @@ class CcInterp(lark.visitors.Interpreter):
             self.visit(tree.children[0])
             op = IfOp(self.cur_fun, [tree.children[0].op.out, mark, has_else])
         self._synth(op)
+        self.cur_fun.regs.drop_temps()
         begin_vars = self.cur_fun.regs.snap()
         self.visit(tree.children[1])
         if has_else:
@@ -1009,6 +1133,7 @@ class CcInterp(lark.visitors.Interpreter):
         postcond = self.cur_fun.regs.snap()
         op = WhileOp(tree.children[0].op.out, mark)
         self._synth(op)
+        self.cur_fun.regs.drop_temps()
         self.visit(tree.children[1])
         self._restore_vars(begin_vars)
         self.cur_fun.ops.append(op.synth_endwhile)
@@ -1023,6 +1148,7 @@ class CcInterp(lark.visitors.Interpreter):
         postcond = self.cur_fun.regs.snap()
         op = WhileOp(tree.children[1].op.out, mark)
         self._synth(op)
+        self.cur_fun.regs.drop_temps()
         self.visit(tree.children[3])
         self.visit(tree.children[2])  # 3rd statement
         self._restore_vars(begin_vars)
@@ -1093,7 +1219,14 @@ class CcInterp(lark.visitors.Interpreter):
         self.cur_fun.deferred_ops.append(Store(self.cur_fun, [reg, var]))
         tree.type = var.type
 
-    pre_increment = _unary_op(Incr)
+    def pre_increment(self, tree):
+        self.visit_children(tree)
+        reg = tree.children[0].op.out
+        tree.op = Incr(self.cur_fun, [reg, reg])
+        self._synth(tree.op)
+        cleanup = lambda reg: self._synth(Store(self.cur_fun, [reg, var]))
+        self.cur_fun.regs.cleanup[reg].append(cleanup)
+
     bool_not = _unary_op(BoolNot)
 
     def _binary_op(op):
@@ -1152,6 +1285,8 @@ class CcInterp(lark.visitors.Interpreter):
         tree.op = tree.children[0].op
 
     def cast(self, tree):
+        if hasattr(tree, 'request_out'):
+            tree.children[1].request_out = tree.request_out
         self.visit_children(tree)
         tree.op = tree.children[1].op
         tree.type = tree.children[0]
@@ -1184,7 +1319,10 @@ class CcInterp(lark.visitors.Interpreter):
         params = fun.param_dict()
 
         def getcleanup(var):
-            return lambda reg: self._synth(Store(self.cur_fun, [reg, var]))
+            def cl(reg):
+                self._log(f'cleanup for {var} in {reg}')
+                self._synth(Store(self.cur_fun, [reg, var]))
+            return cl
 
         for i, param in enumerate(fun.params):
             fun.locals[param.name] = param