Performance dmd vs ldc2
john.loughran.colvin at gmail.com
Wed Jul 31 05:29:31 PDT 2013
On Wednesday, 31 July 2013 at 11:33:01 UTC, Chris wrote:
> On Wednesday, 31 July 2013 at 11:13:13 UTC, John Colvin wrote:
>> On Wednesday, 31 July 2013 at 08:44:30 UTC, Chris wrote:
>>> On Tuesday, 30 July 2013 at 16:43:52 UTC, John Colvin wrote:
>>>> Are you sure that ldc hasn't actually just optimised away
>>>> the whole of parse()?
>>>> Check to asm to be sure.
>>> I've checked the asm output, as you suggested. Turns out that
>>> the DMD version has 94,220 lines and calls parse() for the
>>> first time on line 3278 like so:
>>> call _D10xmlparser25parseFZv at PC32
>>> The LDC version has 14,347 line and calls parse() for the
>>> first time on line 155 like so:
>>> call _D10xmlparser25parseFZv
>>> However, I'm no expert on asm so it's anyone's guess but
>>> mine. But I'm willing to learn.
>> I would suggest doing the following:
>> dmd -c file.d -offiledmd.o
>> ldc2 -c file.d -of=fileldc.o
>> objdump -M intel -dr filedmd.o > filedmd.s
>> objdump -M intel -dr fileldc.o > fileldc.s
>> Then you'll have all the info you need and hopefully a lot
>> less of what you don't need
>> What you're looking for is the definition of parse, like
>> 0000000000000050 <_D10xmlparser25parseFZv>:
>> or similar and then seeing if there's anything much in the
>> function body below.
> Thanks. I've just tried it. In dmd it's there as:
> 00000000 <_D10xmlparser25parseFZv>:
> In ldc too, looks only a bit different. There are:
> 000002b0 <_D10xmlparser25parseFZv>:
Could you post the full asm for those functions?
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