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On 30 Aug 2007, at 19:16, Patrick Donnelly wrote:
I'm curious what kind of compiler optimizations Lua does when creating the byte code, if any? e.g. x = 5 * 32 * i becomes x = 160 * i internally.
Well, the answer is obviously going to vary a bit. But the answer is approximately "almost none".
It does do (some) constant folding. Constants are also pooled. It mostly eliminates redundant branching in conditional forms.
No code-motion (but there's an opcode for for loops); no dead code elimination (the "if false" example you give); no common sub- expression elimination (in the presence of correctly preserving metatable semantics this wouldn't come up very often anyway); no strength reduction; no data-flow analysis.
drj