From: Alan Modra <amodra@gmail.com>
Date: Fri, 1 Jul 2016 11:15:17 +0000 (+0930)
Subject: strcpy arg optimised out
X-Git-Tag: basepoints/gcc-8~5936
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=55dcc361e67fb135be96f5e80e93ee98304b3c1e;p=thirdparty%2Fgcc.git

strcpy arg optimised out

For functions that return an argument unchanged, like strcat,
find_call_crossed_cheap_reg attempts to find an assignment between
a pseudo reg and the arg reg before the call, so that uses of the
pseudo after the call can instead use the return value.  The exit
condition on the loop looking at previous insns was wrong.  Uses of
the arg reg don't matter.  What matters is the insn setting the arg
reg as any assignment involving the arg reg prior to that insn is
likely a completely unrelated use of the hard reg.

	PR rtl-optimization/71709
	* ira-lives.c (find_call_crossed_cheap_reg): Exit loop on arg reg
	being set, not referenced.

From-SVN: r237909
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 685847bf0439..6551c0ec31c3 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2016-07-01  Alan Modra  <amodra@gmail.com>
+
+	PR rtl-optimization/71709
+	* ira-lives.c (find_call_crossed_cheap_reg): Exit loop on arg reg
+	being set, not referenced.
+
 2016-07-01  Yuri Rumyantsev  <ysrumyan@gmail.com>
 
 	PR tree-optimization/70729
diff --git a/gcc/ira-lives.c b/gcc/ira-lives.c
index 6950ffb17b31..6b7ee81bea16 100644
--- a/gcc/ira-lives.c
+++ b/gcc/ira-lives.c
@@ -1014,7 +1014,7 @@ find_call_crossed_cheap_reg (rtx_insn *insn)
 		  break;
 		}
 
-	      if (reg_overlap_mentioned_p (reg, PATTERN (prev)))
+	      if (reg_set_p (reg, prev))
 		break;
 	    }
 	  prev = PREV_INSN (prev);