Remove global call sets: DF (entry/exit defs)

Remove global call sets: DF (entry/exit defs)

The code patched here is seeing whether the current function
needs to save at least part of a register before using it.

2019-09-30  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* df-scan.c (df_get_entry_block_def_set): Use crtl->abi to test
	whether the current function needs to save at least part of a
	register before using it.
	(df_get_exit_block_use_set): Likewise for epilogue restores.

From-SVN: r276320