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Gentlemen-
here is the code sample of the perf. hit challenge
Larry Prevost
NeoVista Solutions, Inc.
408-343-4263
[email protected]
Bug SVRqa08574 DEC Enclosure 1 of 1
cxx Added 960726 by levine
-- cxx generated code performance issue --
Steve,
Here is a piece of code which demonstrates a performance problem
with cxx compiled code. Please let me know if I need to report this by
phone.
Thanks,
Larry
==============================================================
// This fragment shows a performance bug.
// With the error_print() and throw commented out,
// the only memory ops the
// function does relate to fetching a,b,c,d,e.
//
// Evan at highest level of optimization, if the throw is
// present, there is a lot of extraneous memory ops. Since
// throw terminates the function, once the "if(a<0)" is entered
// all the variables u,v,w,x are dead. There is no reason to
// save anything on the stack.
//
// This makes our error checking code very memory intensive
// and expensive since it is forcing state to memory all the time.
//
extern int a,b,c,d,e;
extern int error_print(int);
foo() {
int u = a+b+c+d+e;
int v = a-b+c+d+e;
int w = a+b-c+d+e;
int x = a-+b+c-d+e;
if(a < 0) {
//error_print(a);
// throw a;
;
}
return u + v + w + x;
}
|
| From: US6RMC::"[email protected]" 18-APR-1997 18:35:35.87
To: hydra::lnarayan
CC: [email protected]
Subj: C++ performance problem
Nari-
Sorr for not responding sooner. I've been in contact with some of the
development team and I can't get a straight answer out of anyone or any
kind of supportive information. Why don't you close this out for now
and if it crops up again or if someone has some more solid information,
I'll contact the dec alpha developemnt mailing list. Right now, I
can't get any solid information and I don't want to waste your time or
cause you any undue stress pursuing this. I'll let you know when I
have something more concrete. close this out for now. thanks.
Larry Prevost
NeoVista Software, Inc.
408-343-4263
------- Forwarded Message
Date: Wed, 16 Apr 97 16:30:03 EDT
From: "R Lakshminarayan, Software Partner Engg" <[email protected]>
To: [email protected]
Cc: [email protected]
Subject: Re: C++ performance problem
Larry Prevost
This is with reference to the C++ performance problem that you had
reported, I got an example code with function foo relating to the
problem that you had reported. But I had requested for a complete code
example. I would like to request you send the code so that I can
work on this.
Thank You
- -Nari
Alpha developer support
Digital Equipment Corp.
------- End of Forwarded Message
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