[patch,libfortran] [4.7/4.8/4.9 Regression] PR38199 missed optimization: I/O performance

[Jerry DeLisle]

On 03/09/2014 05:39 PM, Jerry DeLisle wrote:
> Hi all,
> 
> This final patch does two things.
> 
> First:  In read.c it implements a simple space skipping scheme in read_decimal
> where I found a lot of repeated next_char calls happening. This gives a pretty
> good boost in performance and is applicable in general for reading integers.
> 
> Second: I have taken Thomas idea of using LEN_TRIM in unit.c revised it to work
> on formatted READ.  I tried to document the code with comments.  There are
> certain conditions for which one can not shorten the string length for internal
> units. For arrays of characters you can not do this for strings more than rank 1
> and stride 1. Also, you can not do this any time a BLANK='zero' is being used. I
> also skip the optimization if there is any BLANK= specified in the READ. Thats
> conservative.  I could also test for BLANK='NULL' in the DTP structure. I will
> probably do that later.
> 
> I have added a helper function which tests for the BZ within a format string
> when a format string is present.  I also check to see if the UNIT has had the
> BLANK status set.  The optimization is skipped for these conditions.
> 
Updated patch to resolve issue found during NIST tests.

Regression tested and NIST tested.

OK for trunk?

Regards,

Jerry

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