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/src/verifier/mod.rs

@@ -335,6 +335,12 @@ impl<'a> Verifier<'a> {
             RegFill { src, .. } => {
                 self.verify_stack_slot(inst, src)?;
             }
+            LoadComplex { ref args, .. } => {
+                self.verify_value_list(inst, args)?;
+            }
+            StoreComplex { ref args, .. } => {
+                self.verify_value_list(inst, args)?;
+            }
 
             // Exhaustive list so we can't forget to add new formats
             Unary { .. } |
@@ -1149,8 +1155,8 @@ impl<'a> Verifier<'a> {
 mod tests {
     use super::{Error, Verifier};
     use entity::EntityList;
-    use ir::Function;
     use ir::instructions::{InstructionData, Opcode};
+    use ir::Function;
     use settings;
 
     macro_rules! assert_err_with_msg {