Define register banks.

Add a RegBank class for describing CPU register banks.

Define register banks for all the ISA stubs. The ARM32 floating point
bank in particular requires attention.

lib/cretonne/meta/isa/arm32/registers.py

@@ -0,0 +1,29 @@
+"""
+ARM32 register banks.
+"""
+from __future__ import absolute_import
+from cdsl.registers import RegBank
+from .defs import ISA
+
+
+# Special register units:
+# - r15 is the program counter.
+# - r14 is the link register.
+# - r13 is usually the stack pointer.
+IntRegs = RegBank(
+        'IntRegs', ISA,
+        'General purpose registers',
+        units=16, prefix='r')
+
+FloatRegs = RegBank(
+        'FloatRegs', ISA, r"""
+        Floating point registers.
+
+        The floating point register units correspond to the S-registers, but
+        extended as if there were 64 registers.
+
+        - S registers are one unit each.
+        - D registers are two units each, even D16 and above.
+        - Q registers are 4 units each.
+        """,
+        units=64, prefix='s')