load_complex and store_complex instructions (#309)

* Start adding the load_complex and store_complex instructions.

N.b.:
The text format is not correct yet. Requires changes to the lexer and parser.
I'm not sure why I needed to change the RuntimeError to Exception yet. Will fix.

* Get first few encodings of load_complex working. Still needs var args type checking.

* Clean up ModRM helper functions in binemit.

* Implement 32-bit displace for load_complex

* Use encoding helpers instead of doing them all by hand

* Initial implementation of store_complex

* Parse value list for load/store_complex with + as delimiter. Looks nice.

* Add sign/zero-extension and size variants for load_complex.

* Add size variants of store_complex.

* Add asm helper lines to load/store complex bin tests.

* Example of length-checking the instruction ValueList for an encoding. Extremely questionable implementation.

* Fix Python linting issues

* First draft of postopt pass to fold adds and loads into load_complex. Just simple loads for now.

* Optimization pass now works with all types of loads.

* Add store+add -> store_complex to postopt pass

* Put complex address optimization behind ISA flag.

* Add load/store complex for f32 and f64

* Fixes changes to lexer that broke NaN parsing.

Abstracts away the repeated checks for whether or not the characters
following a + or - are going to be parsed as a number or not.

* Fix formatting issues

* Fix register restrictions for complex addresses.

* Encoding tests for x86-32.

* Add documentation for newly added instructions, recipes, and cdsl changes.

* Fix python formatting again

* Apply value-list length predicates to all LoadComplex and StoreComplex instructions.

* Add predicate types to new encoding helpers for mypy.

* Import FieldPredicate to satisfy mypy.

* Add and fix some "asm" strings in the encoding tests.

* Line-up 'bin' comments in x86/binary64 test

* Test parsing of offset-less store_complex instruction.

* 'sNaN' not 'sNan'

* Bounds check the lookup for polymorphic typevar operand.

* Fix encodings for istore16_complex.

lib/codegen/meta/cdsl/instructions.py

@@ -201,9 +201,10 @@ class Instruction(object):
         # Prefer to use the typevar_operand to infer the controlling typevar.
         self.use_typevar_operand = False
         typevar_error = None
-        if self.format.typevar_operand is not None:
+        tv_op = self.format.typevar_operand
+        if tv_op is not None and tv_op < len(self.value_opnums):
             try:
-                opnum = self.value_opnums[self.format.typevar_operand]
+                opnum = self.value_opnums[tv_op]
                 tv = self.ins[opnum].typevar
                 if tv is tv.free_typevar() or tv.singleton_type() is not None:
                     self.other_typevars = self._verify_ctrl_typevar(tv)