Patch to improve PIC find_base_term

Jeffrey A Law law@cygnus.com
Mon Aug 21 05:54:00 GMT 2000


  In message < 200008210411.AAA00718@jwlab.FEITH.COM >you write:
  > This patch allows alias analysis to understand PIC addresses.  The
  > BRL-CAD raytracing benchmarks show 1-5 percent improvement with it.
  > This patch passes make bootstrap and make check on FreeBSD-3.5 x86.
  > 
  > ChangeLog:
  > 
  > Mon Aug 21 00:00:24 EDT 2000  John Wehle  (john@feith.com)
  > 
  > 	* alias.c (find_base_term): Handle the pic register.
I don't think we want to put this into alias.c in its current form -- 
basically you're peeking inside an UNSPEC and making assumptions about
the meaning of what you find inside the UNSPEC.

That seems bad.

I suspect the basic problem is that you want to find some way to get
a valid base term when you see a reference to pic_offset_table_rtx.  But
there is no standard way to derive the base term in that case.

I wouldn't mind having a callout to a target dependent routine to do this
kind of groveling around inside UNSPECs, or generally, given a reference
to the PIC register, a routine to find its associated symbol which used
backend routines.

jeff



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