diff mbox

[PR,tree-optimization/69196] Consider two anonymous SSA_NAMEs unassociated

Message ID 56DA6B42.6010009@redhat.com
State New
Headers show

Commit Message

Jeff Law March 5, 2016, 5:14 a.m. UTC 
As pointed out by Richi, the code did not precisely match the comment in 
the case of two anonymous SSA_NAMEs.

In that case we don't have enough information to determine if the names 
are associated.  Until we do something like build partitions (similar to 
what's done in tree-ssa-coalesce), it seems best to consider two 
anonymous SSA_NAMEs to be unassociated and count the PHI against the 
statement count for threading.

Bootstrapped and regression tested on x86-64.  Installed on the trunk.

Jeff
commit 2ef58c4014fc23573d8ff10e50381c6cbdcba6e6
Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
Date:   Sat Mar 5 05:10:58 2016 +0000

    	PR tree-optimization/69196
    	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
    	If the both SSA_NAMEs are anonymous, then consider them unassociated
    	and include the PHI in the statement count.
    
    git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@233999 138bc75d-0d04-0410-961f-82ee72b054a4
diff mbox

Patch

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5c23836..09a2714 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@ 
+2016-03-04  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/69196
+	* tree-ssa-threadbackward.c (fsm_find_control_statement_thread_paths):
+	If the both SSA_NAMEs are anonymous, then consider them unassociated
+	and include the PHI in the statement count.
+
 2016-03-05  Tom de Vries  <tom@codesourcery.com>
 
 	* omp-low.c (check_omp_nesting_restrictions): Check for non-oacc
diff --git a/gcc/tree-ssa-threadbackward.c b/gcc/tree-ssa-threadbackward.c
index 747296b..6f1b757 100644
--- a/gcc/tree-ssa-threadbackward.c
+++ b/gcc/tree-ssa-threadbackward.c
@@ -311,7 +311,11 @@  fsm_find_control_statement_thread_paths (tree name,
 			  gphi *phi = gsip.phi ();
 			  tree dst = gimple_phi_result (phi);
 
-			  if (SSA_NAME_VAR (dst) != SSA_NAME_VAR (name)
+			  /* Note that if both NAME and DST are anonymous
+			     SSA_NAMEs, then we do not have enough information
+			     to consider them associated.  */
+			  if ((SSA_NAME_VAR (dst) != SSA_NAME_VAR (name)
+			       || !SSA_NAME_VAR (dst))
 			      && !virtual_operand_p (dst))
 			    ++n_insns;
 			}