From: Chung-Lin Tang <cltang@codesourcery.com>
Date: Fri, 28 Oct 2011 06:35:31 +0000 (+0000)
Subject: re PR rtl-optimization/49720 (Infinite recursion compiling gold binary_test.cc testcase)
X-Git-Tag: releases/gcc-4.7.0~2749
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=d303c992f61f5f94aaa314e914b1e27280940de2;p=thirdparty%2Fgcc.git

re PR rtl-optimization/49720 (Infinite recursion compiling gold binary_test.cc testcase)

2011-10-28  Chung-Lin Tang  <cltang@codesourcery.com>

	PR rtl-optimization/49720
	* simplify-rtx.c (simplify_relational_operation_1): Detect
	infinite recursion condition in "(eq/ne (plus x cst1) cst2)
	simplifies to (eq/ne x (cst2 - cst1))" case.

	testsuite/
	* g++.dg/torture/pr49720.C: New test.

From-SVN: r180604
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 420e188b91ed..61320f852ab7 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,10 @@
+2011-10-28  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	PR rtl-optimization/49720
+	* simplify-rtx.c (simplify_relational_operation_1): Detect
+	infinite recursion condition in "(eq/ne (plus x cst1) cst2)
+	simplifies to (eq/ne x (cst2 - cst1))" case.
+
 2011-10-27  David S. Miller  <davem@davemloft.net>
 
 	* config/sparc/sparc.md (snedi_special): Only match when not VIS3.
diff --git a/gcc/simplify-rtx.c b/gcc/simplify-rtx.c
index 130161698596..ab888a96db84 100644
--- a/gcc/simplify-rtx.c
+++ b/gcc/simplify-rtx.c
@@ -4352,10 +4352,20 @@ simplify_relational_operation_1 (enum rtx_code code, enum machine_mode mode,
     {
       rtx x = XEXP (op0, 0);
       rtx c = XEXP (op0, 1);
+      enum rtx_code invcode = op0code == PLUS ? MINUS : PLUS;
+      rtx tem = simplify_gen_binary (invcode, cmp_mode, op1, c);
+
+      /* Detect an infinite recursive condition, where we oscillate at this
+	 simplification case between:
+	    A + B == C  <--->  C - B == A,
+	 where A, B, and C are all constants with non-simplifiable expressions,
+	 usually SYMBOL_REFs.  */
+      if (GET_CODE (tem) == invcode
+	  && CONSTANT_P (x)
+	  && rtx_equal_p (c, XEXP (tem, 1)))
+	return NULL_RTX;
 
-      c = simplify_gen_binary (op0code == PLUS ? MINUS : PLUS,
-			       cmp_mode, op1, c);
-      return simplify_gen_relational (code, mode, cmp_mode, x, c);
+      return simplify_gen_relational (code, mode, cmp_mode, x, tem);
     }
 
   /* (ne:SI (zero_extract:SI FOO (const_int 1) BAR) (const_int 0))) is
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9ef38fc4c0b6..c63184cbd1b1 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2011-10-28  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	PR rtl-optimization/49720
+	* g++.dg/torture/pr49720.C: New test.
+
 2011-10-27  David S. Miller  <davem@davemloft.net>
 
 	* gcc.target/sparc/setcc-3.c: New test.
diff --git a/gcc/testsuite/g++.dg/torture/pr49720.C b/gcc/testsuite/g++.dg/torture/pr49720.C
new file mode 100644
index 000000000000..c5da7ba670f1
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr49720.C
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+
+extern char t_start[], t_end[], t_size[];
+bool foo (void)
+{
+  long size = reinterpret_cast<long>(t_size);
+  return (size == t_end - t_start);
+}