[PATCH] Correctly validate free registers for peep2

[Richard Earnshaw <rearnsha at arm dot com>]

PR 57708 is a bug where peep2_find_free_register is incorrectly
returning a register that clobbers an unsaved callee saved register.
The problem is due to the way it validates register liveness: only the
first register in the list is fully validated.  In this particular case
the problem is that the second register has not been saved in the
prologue, but all of the tests except the suitability for the mode need
to be performed for each register.

	*recog.c (peep2_find_free_register): Validate all regs in a
	multi-reg mode.

Bootstrapped on x86_64.

Ok for trunk and 4.8?  (4.7 is also affected, but I don't know of any
back-end relies on this at that point).

R.

Attachment: peephole.patch
Description: Text document