#208 Optimizing [if {[string compare]} ...]

[Donal K. Fellows]

This patch converts [string compare] so that it
generates INST_STR_EQ;INST_LNOT instead of INST_STR_CMP
when the comparison is going to be used as a boolean
test in the [if], [for] and [while] commands. This
should be faster, particularly on longer strings,
because we don't need to know how the strings differ.
Part of the patch could be construed to form the basis
for a more general optimization framework, but that
probably needs more work to realize...

[Donal K. Fellows]

Optimizer Patch (UniDiff)

[miguel sofer]

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Updated patch (after HEAD modifs due to [Bug 562383].

[miguel sofer]

updated patch

[Jeffrey Hobbs]

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While this looks good in general, I'd prefer focusing on a post-
pass optimizer that can look at the whole tree and streamline
such cases globally. Thus we could also get rid of the
INST_TRY_CVT_NUMERIC in many cases, along with finding
INST_STR_CMP == 0 static, which is INST_STR_EQ, etc.

[miguel sofer]

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After so many years ... we'll eventually have the
post-optimiser.

[SourceForge Robot]

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This Tracker item was closed automatically by the system. It was
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[Donal K. Fellows]

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Assigned to me so I remember to revisit this once we've
solved the general optimization stuff.