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Re: RFA: patch for PR42973


Steven Bosscher wrote:
On Tue, Feb 9, 2010 at 9:00 PM, Vladimir Makarov <vmakarov@redhat.com> wrote:
+ for (link = REG_NOTES (insn); link; link = XEXP (link, 1))
+ if (REG_NOTE_KIND (link) == REG_DEAD)
+ break;
+ if (! link)
+ return;

What is the purpose of this code? Obviously you're looking for a
REG_DEAD note, but you're not looking at this note anywhere to see
which reg dies.
If there are no REG_DEAD notes, there is no sense to try copy generation. The code in the function after the mentioned code is expensive. So major purpose of the code fragment is to speed up constraint and shuffle copy generation.


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