Add legalization patterns.

meta/cretonne/legalize.py

@@ -0,0 +1,48 @@
+"""
+Patterns for legalizing the `base` instruction set.
+
+The base Cretonne instruction set is 'fat', and many instructions don't have
+legal representations in a given target ISA. This module defines legalization
+patterns that describe how base instructions can be transformed to other base
+instructions that are legal.
+"""
+from __future__ import absolute_import
+from .base import iadd, iadd_cout, iadd_cin, isplit_lohi, iconcat_lohi
+from .base import isub, isub_bin, isub_bout
+from .ast import Var
+from .xform import Rtl, XFormGroup
+
+
+narrow = XFormGroup()
+
+x = Var('x')
+y = Var('y')
+a = Var('a')
+b = Var('b')
+c = Var('c')
+xl = Var('xl')
+xh = Var('xh')
+yl = Var('yl')
+yh = Var('yh')
+al = Var('al')
+ah = Var('ah')
+
+narrow.legalize(
+        a << iadd(x, y),
+        Rtl(
+            (xl, xh) << isplit_lohi(x),
+            (yl, yh) << isplit_lohi(y),
+            (al, c) << iadd_cout(xl, yl),
+            ah << iadd_cin(xh, yh, c),
+            a << iconcat_lohi(al, ah)
+        ))
+
+narrow.legalize(
+        a << isub(x, y),
+        Rtl(
+            (xl, xh) << isplit_lohi(x),
+            (yl, yh) << isplit_lohi(y),
+            (al, b) << isub_bout(xl, yl),
+            ah << isub_bin(xh, yh, b),
+            a << iconcat_lohi(al, ah)
+        ))