[PATCH 04/25] SPECIAL_REGNO_P

[ams@codesourcery.com]

GCN has some registers which are special purpose, but not "fixed" because we
want the register allocator to track their usage and select alternatives that
use different special registers (e.g. scalar cc vs. vector cc).

Sometimes this leads the regrename pass to ICE.  Quite how it gets confused is
not well understood, but considering such registers for renaming is surely not
useful.

This patch creates a new macro SPECIAL_REGNO_P which disables regrename.  In
other words, the register is fixed once allocated.

2018-09-05  Kwok Cheung Yeung  <kcy@codesourcery.com>

	gcc/
	* defaults.h (SPECIAL_REGNO_P): Define to false by default.
	* regrename.c (check_new_reg_p): Do not rename to a special register.
	(rename_chains): Do not rename special registers.
---
 gcc/defaults.h  | 4 ++++
 gcc/regrename.c | 2 ++
 2 files changed, 6 insertions(+)

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