bf2a54b058
Recently @sergey found that hard-coding evaluation of certain very common driver expressions without calling the Python interpreter produces a 30-40% performance improvement. Since hard-coding is obviously not suitable for production, I implemented a proper parser and interpreter for simple arithmetic expressions in C. The evaluator supports +, -, *, /, (), ==, !=, <, <=, >, >=, and, or, not, ternary if; driver variables, frame, pi, True, False, and a subset of standard math functions that seem most useful. Booleans are represented as numbers, since within the supported operation set it seems to be impossible to distinguish True/False from 1.0/0.0. Boolean operations properly implement lazy evaluation with jumps, and comparisons support chaining like 'a < b < c...'. Expressions are parsed into a very simple stack machine program that can then be safely evaluated in multiple threads. Reviewers: sergey, campbellbarton Differential Revision: https://developer.blender.org/D3698