Define control flow instructions.

Rename 'br' to 'jump'. We'll use jump/br to mean unconditional/conditional
control transfer respectively.

meta/cretonne/formats.py

@@ -9,7 +9,7 @@ in this module.
 
 from . import InstructionFormat, value, variable_args
 from immediates import imm64, ieee32, ieee64, immvector
-from entities import function
+from entities import ebb, function, jump_table
 
 Nullary = InstructionFormat()
 
@@ -23,6 +23,10 @@ Binary = InstructionFormat(value, value)
 BinaryImm = InstructionFormat(value, imm64)
 BinaryImmRev = InstructionFormat(imm64, value)
 
+Jump = InstructionFormat(ebb, variable_args)
+Branch = InstructionFormat(value, ebb, variable_args)
+BranchTable = InstructionFormat(value, jump_table)
+
 Call = InstructionFormat(function, variable_args, multiple_results=True)
 
 # Finally extract the names of global variables in this module.