Fix CC_MODE pessimization in reorg.c

[Eric Botcazou]

As exposed in https://gcc.gnu.org/ml/gcc-patches/2014-12/msg01052.html the 
conversion of the original cc0-based Visium port into a CC_MODE port went 
smoothly and didn't affect the run time performance, except for a single but 
notable case: the reorg.c pass cannot put an insn that clobbers the CC reg 
into a conditional branch's delay slot if it comes from before the branch.
I guess this is negligible on most architectures with delay slots but not on 
the Visium where it alone costs 3% on CoreMark.

The attached patch fixes the pessimization very selectively, using the same 
trigger as the compare-elim pass, which means that only aarch64, mn10300, rx 
and visium are potentially affected; now among them only visium has delay 
slots so the patch actually affects visium only.

Tested on visium-elf.  Any objections to me applying it now?


2015-01-16  Eric Botcazou  <ebotcazou@adacore.com>

	* reorg.c (fill_simple_delay_slots): If TARGET_FLAGS_REGNUM is valid,
	implement a more precise life analysis for it during backward scan.


-- 
Eric Botcazou
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