r273569 - in /trunk/gcc: ChangeLog basic-block....

[rsandifo@gcc.gnu.org]

Author: rsandifo
Date: Thu Jul 18 08:24:16 2019
New Revision: 273569

URL: https://gcc.gnu.org/viewcvs?rev=273569&root=gcc&view=rev
Log:
Make ifcvt clean up dead comparisons

This change is needed to avoid a regression in gcc.dg/ifcvt-3.c
for a later patch.  Without it, we enter CSE with a dead comparison left
by if-conversion and then eliminate the second (live) comparison in
favour of the dead one.  That's functionally correct in itself, but it
meant that we'd combine the subtraction and comparison into a SUBS
before we have a chance to fold away the subtraction.

2019-07-18  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* basic-block.h (CLEANUP_FORCE_FAST_DCE): New macro.
	* cfgcleanup.c (cleanup_cfg): Call run_fast_dce if
	CLEANUP_FORCE_FAST_DCE is set.
	* ifcvt.c (rest_of_handle_if_conversion): Pass
	CLEANUP_FORCE_FAST_DCE to the final cleanup_cfg call if
	if-conversion succeeded.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/basic-block.h
    trunk/gcc/cfgcleanup.c
    trunk/gcc/ifcvt.c