rs6000.h (FIXED_SCRATCH): Use r0 as a scratch register on SPE targets.

rs6000.h (FIXED_SCRATCH): Use r0 as a scratch register on SPE targets.

	* config/rs6000/rs6000.h (FIXED_SCRATCH): Use r0 as a scratch
	register on SPE targets.  Change documentation to reflect
	reality.
	* config/rs6000/rs6000.c (rs6000_conditional_register_usage):
	Change FIXED_SCRATCH to 14 and document why we're keeping r14
	out of the register allocation pool.
	(rs6000_reg_live_or_pic_offset_p): New function.
	(rs6000_emit_prologue): Move the actual saving of LR up to free
	r0 for holding r11.  Split saving of SPE 64-bit registers into
	its own case.  Ensure that offsets will always be in-range for
	'evstdd' by using r11 as a scratch register to point at the start
	of the SPE save area.  Save r11 if necessary, as it is the static
	chain register.
	(rs6000_emit_epilogue): Split restoring of SPE 64-bit registers
	into its own case.  Ensure that offsets will always be in-range
	for 'evldd' by using r11 as a scratch register to point at the
	start of the SPE save area.  Also adjust r11 when restoring
	the stack pointer to compensate for pre-loading r11.

From-SVN: r125340