Fix bug when indices are computed using subtraction in loops.

Compiler/allocator.py

@@ -781,10 +781,10 @@ def __init__(self):
         self.rev_offset_cache = {}
         self.range_cache = util.dict_by_id()
 
-    def add_offset(self, res, new_base, new_offset):
-        self.offset_cache[res] = new_base, new_offset
-        if (new_base.i, new_offset) not in self.rev_offset_cache:
-            self.rev_offset_cache[new_base.i, new_offset] = res
+    def add_offset(self, res, new_base, new_offset, multiplier):
+        self.offset_cache[res] = new_base, new_offset, multiplier
+        if (new_base.i, new_offset, multiplier) not in self.rev_offset_cache:
+            self.rev_offset_cache[new_base.i, new_offset, multiplier] = res
 
     def run(self, instructions, program):
         for i, inst in enumerate(instructions):
@@ -808,31 +808,40 @@ def run(self, instructions, program):
                     def f(base, delta_reg):
                         delta = self.cache[delta_reg]
                         if base in self.offset_cache:
-                            reg, offset = self.offset_cache[base]
+                            reg, offset, mult = self.offset_cache[base]
                             new_base, new_offset = reg, offset + delta
                         else:
                             new_base, new_offset = base, delta
-                        self.add_offset(inst.args[0], new_base, new_offset)
+                            mult = 1
+                        self.add_offset(inst.args[0], new_base, new_offset,
+                                        mult)
                     if inst.args[1] in self.cache:
                         f(inst.args[2], inst.args[1])
                     elif inst.args[2] in self.cache:
                         f(inst.args[1], inst.args[2])
-                elif isinstance(inst, subint_class) and \
-                     inst.args[2] in self.cache:
-                    delta = self.cache[inst.args[2]]
-                    if inst.args[1] in self.offset_cache:
-                        reg, offset = self.offset_cache[inst.args[1]]
-                        new_base, new_offset = reg, offset - delta
-                    else:
-                        new_base, new_offset = inst.args[1], -delta
-                    self.add_offset(inst.args[0], new_base, new_offset)
+                elif isinstance(inst, subint_class):
+                    def f(reg, cached, reverse):
+                        delta = self.cache[cached]
+                        if reg in self.offset_cache:
+                            reg, offset, mult = self.offset_cache[reg]
+                            new_base, new_offset = reg, offset - delta
+                        else:
+                            new_base = reg
+                            new_offset = -delta if reverse else delta
+                            mult = 1
+                        self.add_offset(inst.args[0], new_base, new_offset,
+                                        mult if reverse else -mult)
+                    if inst.args[1] in self.cache:
+                        f(inst.args[2], inst.args[1], False)
+                    elif inst.args[2] in self.cache:
+                        f(inst.args[1], inst.args[2], True)
             elif isinstance(inst, IndirectMemoryInstruction):
                 if inst.args[1] in self.cache:
                     instructions[i] = inst.get_direct(self.cache[inst.args[1]])
                     instructions[i]._protect = inst._protect
                 elif inst.args[1] in self.offset_cache:
-                    base, offset = self.offset_cache[inst.args[1]]
-                    addr = self.rev_offset_cache[base.i, offset]
+                    base, offset, mult = self.offset_cache[inst.args[1]]
+                    addr = self.rev_offset_cache[base.i, offset, mult]
                     inst.args[1] = addr
                 elif inst.args[1] in self.range_cache:
                     size, base = self.range_cache[inst.args[1]]