[Python-Dev] Python-acceleration instructions on ARM (original) (raw)

Cesare Di Mauro cesare.dimauro at a-tono.com
Wed Feb 11 13:56:21 CET 2009

Antoine Pitrou <solipsis at pitrou.net> wrote:

Martin v. Löwis <martin v.loewis.de> writes:

- efficient array indexing: they give shift-and-index back to Thumb mode, for a shift by 2, allowing to index arrays with 4-byte elements in a single instruction (rather than requiring a separate multipy-by-four). Again useful for JIT of array access instructions, not applicable to Python - although it would be nice if the C compiler knew how to emit that. This could be used in PyTupleGetItem and PyListGetItem, no?

Yes, but it's a compiler (Thumb-EE specific back-end) burden.

Otherwise, we can introduce Thumb-EE assembly code were needed, but the same can happen for a wide range of ISAs.

At least IA32 and AMD64 have specific addressing modes where it's possibile to use a multiplying factor of 1, 2, 4 or 8 for the index register.

I hope that compilers were smart enough to already used them.

(assuming Thumb has 4-byte pointers)

Yes, it does.

Cesare

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