r242488 - in /trunk/gcc: ChangeLog cprop.c

[rsandifo@gcc.gnu.org]

Author: rsandifo
Date: Wed Nov 16 13:07:08 2016
New Revision: 242488

URL: https://gcc.gnu.org/viewcvs?rev=242488&root=gcc&view=rev
Log:
Use df_read_modify_subreg_p in cprop.c

local_cprop_find_used_regs punted on all multiword registers,
with the comment:

          /* Setting a subreg of a register larger than word_mode leaves
             the non-written words unchanged.  */

But this only applies if the outer mode is smaller than the
inner mode.  If they're the same size then writes to the subreg
are a normal full update.

This patch uses df_read_modify_subreg_p instead.  A later patch
adds more uses of the same routine, but this part had a (positive)
effect on code generation for the testsuite whereas the others
seemed to be simple clean-ups.

gcc/
2016-11-15  Richard Sandiford  <richard.sandiford@arm.com>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

	* cprop.c (local_cprop_find_used_regs): Use df_read_modify_subreg_p.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/cprop.c