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Re: GCSE store motion


On Wed, 15 May 2002, Roger Sayle wrote:

> 
> > In addition, never, in any RTL dumps of any code, ever, have I seen it
> > remove a single store.
> 
> I'd suggest compiling the testcase in the patch below with -O3 on CVS
> mainline (before store motion was disabled).  The test is ill-formed
> and the duplicate store should be moved, the call to abort() reveals
> that the optimizer did its job.  Feel free to step through with a
> debuggger to convince yourself that it was GCSE's store motion at
> work.  For example, it doesn't abort compiling with "-O3 -fno-gcse".
> 
> Seeing is believing.
Yes, as I mentioned, I misspoke. It now 
removes 2 stores through global store removal during compilation of gcc, and moves 
3.

You still haven't addressed the issues I raised.
You simply ignored them.

The fact that store motion removes a single store in compilation of glibc 
at -O3 does not make it useful.
I've provided evidence that it is not useful.
This is in the form of statements by the person who wrote it, SPEC runs, 
statistics on the number of stores removed during bootstrapping gcc, etc.

No data or person has claimed, besides you, that store motion in it's 
current form is useful.

Please provide evidence it is, since all evidence points to the contrary.

 > 
> Roger
> --
> 


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