[New-bugs-announce] [issue27127] Never have GET_ITER not followed by FOR_ITER

[Demur Rumed]

New submission from Demur Rumed:

This is a small change to comprehensions pass in their iterable rather than calling GET_ITER before CALL_FUNCTION. This makes it so that the compiler never generates GET_ITER without following it with FOR_ITER, nor does it generate FOR_ITER without preceding it by GET_ITER

This is the standalone portion of a more constructive patch I'm wanting to submit: Replace GET_ITER with a FOR_BEGIN which effectively acts as GET_ITER/FOR_ITER. Then modify FOR_ITER to replace the JUMP_ABSOLUTE by changing it to a JABS instruction which jumps if the iterator does not return null. This reduces the bytecode of by 2 bytes for every for loop & reduces the dispatch count per loop by 1 (As we merge GET_ITER/FOR_ITER & JUMP_ABSOLUTE/FOR_ITER)

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components: Interpreter Core
files: gitfit.patch
keywords: patch
messages: 266400
nosy: Demur Rumed
priority: normal
severity: normal
status: open
title: Never have GET_ITER not followed by FOR_ITER
type: performance
versions: Python 3.6
Added file: http://bugs.python.org/file43006/gitfit.patch

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue27127>
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