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Re: gcc/resource.c mark_target_live_regs Question
- To: oldham at codesourcery dot com
- Subject: Re: gcc/resource.c mark_target_live_regs Question
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- Date: Wed, 14 Feb 01 19:26:45 EST
- Cc: gcc at gcc dot gnu dot org
Why does resource.c's mark_target_live_regs() start computing live
registers at the previous BARRIER rather than the beginning of the
basic block containing the target? For functions with lots of
instructions but few BARRIERs, this can lead to O(n^2) performance
even if the function has many basic blocks.
It originally did this because register death information on hard regs
was not accurate after reload. I don't know if this is still true.