# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1209336790 -7200
# Node ID 7afa1b5f52cee1ca43991b8c9aba5e1619a5047e
# Parent  d4884c5a16e970e3ce145758d8547fc419ddb084
Attempted to add optimisations around temporary storage access.

diff -r d4884c5a16e9 -r 7afa1b5f52ce micropython/ast.py
--- a/micropython/ast.py	Sun Apr 27 21:05:55 2008 +0200
+++ b/micropython/ast.py	Mon Apr 28 00:53:10 2008 +0200
@@ -48,7 +48,7 @@
 
     "A translated module."
 
-    supported_optimisations = ["constant_storage", "known_target", "self_access"]
+    supported_optimisations = ["constant_storage", "known_target", "self_access", "temp_storage"]
 
     def __init__(self, module, importer, optimisations=None):
 
@@ -255,6 +255,7 @@
                 return
 
             # Get the details of the access.
+            # NOTE: Support constants here.
 
             target = last.attr.value
             target_name = target.full_name()
@@ -271,6 +272,8 @@
                 raise TranslateError(self.module.full_name(), node,
                     "No attribute entry exists for name %r in target %r." % (attrname, target_name))
 
+            # NOTE: Support constants here.
+
             if isinstance(target, micropython.inspect.Instance):
                 self.replace_op(AttrInstruction(pos))
             else:
@@ -547,6 +550,9 @@
     def _should_optimise_self_access(self):
         return "self_access" in self.optimisations
 
+    def _should_optimise_temp_storage(self):
+        return "temp_storage" in self.optimisations
+
     def _have_constant_input(self, n):
         last = self.last_ops(n+1)
         return len(last) > n and (isinstance(last[n], LoadAddress) and last[n].attr.assignments == 1 or
@@ -561,8 +567,32 @@
             self.unit.is_method() and isinstance(last, LoadName) and \
             last.attr.name == "self"
 
+    def _have_temp_compatible_access(self):
+        last = self.last_op()
+        # NOTE: Should expand to cover LoadAttr and LoadAttrIndex, but this
+        # NOTE: would require inspection of the stack operands.
+        return isinstance(last, (LoadName, LoadTemp, LoadAddress))
+
     # Optimisation methods. See the supported_optimisations class attribute.
 
+    def _optimise_temp_storage(self):
+
+        """
+        Where the next operation would involve storing a value into temporary
+        storage, record and remove any simple instruction which produced the
+        value such that instead of subsequently accessing the temporary storage,
+        that instruction is substituted.
+        """
+
+        if self._should_optimise_temp_storage() and \
+            self._have_temp_compatible_access():
+
+            last = self.last_op()
+            self.remove_ops(1)
+            return last
+        else:
+            return None
+
     def _optimise_constant_storage(self, instruction, n):
 
         """
@@ -647,22 +677,31 @@
         right_label = self.new_label()
         end_label = self.new_label()
 
-        # NOTE: Decide on temporary storage access.
+        # NOTE: Potentially remove the reservation if optimised storage is used.
 
         temp_position = self.reserve_temp(2)
 
         self.dispatch(node.left)
-        self.new_op(StoreTemp(temp_position))
+
+        temp1 = self._optimise_temp_storage()
+        if not temp1:
+            self.new_op(StoreTemp(temp_position))
+            temp1 = LoadTemp(temp_position)
+
         self.dispatch(node.right)
-        self.new_op(StoreTemp(temp_position + 1))
+
+        temp2 = self._optimise_temp_storage()
+        if not temp2:
+            self.new_op(StoreTemp(temp_position + 1))
+            temp2 = LoadTemp(temp_position + 1)
 
         # Left method.
 
         self._startCallFunc()
-        self.new_op(LoadTemp(temp_position))
+        self.new_op(temp1)
         self._generateAttr(node, left_method, (LoadAddress, LoadAttr, LoadAttrIndex))
-        self.new_op(LoadTemp(temp_position)) # Explicit context as first argument.
-        self.new_op(LoadTemp(temp_position + 1))
+        self.new_op(temp1) # Explicit context as first argument.
+        self.new_op(temp2)
         self._endCallFunc()
 
         self.dispatch(compiler.ast.Name("AttributeError"))
@@ -673,10 +712,10 @@
 
         self.set_label(right_label)
         self._startCallFunc()
-        self.new_op(LoadTemp(temp_position + 1))
+        self.new_op(temp2)
         self._generateAttr(node, right_method, (LoadAddress, LoadAttr, LoadAttrIndex))
-        self.new_op(LoadTemp(temp_position + 1)) # Explicit context as first argument.
-        self.new_op(LoadTemp(temp_position))
+        self.new_op(temp2) # Explicit context as first argument.
+        self.new_op(temp1)
         self._endCallFunc()
 
         self.set_label(end_label)