re PR rtl-optimization/50380 ([4.6 only] cc1 hangs eating 100% CPU)

2011-12-19  Sandra Loosemore  <sandra@codesourcery.com>
	    Tom de Vries <tom@codesourcery.com>

	PR rtl-opt/50380

	gcc/
	* cse.c (find_comparison_args): Detect fixed point and
	bail early.

	gcc/testsuite/
	* gcc.c-torture/compile/pr50380.c: New testcase.

Co-Authored-By: Tom de Vries <tom@codesourcery.com>

From-SVN: r182498

gcc/ChangeLog

+2011-12-19  Sandra Loosemore  <sandra@codesourcery.com>
+	    Tom de Vries <tom@codesourcery.com>
+
+	PR rtl-opt/50380
+	* cse.c (find_comparison_args): Detect fixed point and
+	bail early.
+
 2011-12-19  Aldy Hernandez  <aldyh@redhat.com>
 
 	PR middle-end/51411

gcc/cse.c

@@ -3055,6 +3055,12 @@ find_comparison_args (enum rtx_code code, rtx *parg1, rtx *parg2,
 	  if (! exp_equiv_p (p->exp, p->exp, 1, false))
 	    continue;
 
+	  /* If it's the same comparison we're already looking at, skip it.  */
+	  if (COMPARISON_P (p->exp)
+	      && XEXP (p->exp, 0) == arg1
+	      && XEXP (p->exp, 1) == arg2)
+	    continue;
+
 	  if (GET_CODE (p->exp) == COMPARE
 	      /* Another possibility is that this machine has a compare insn
 		 that includes the comparison code.  In that case, ARG1 would

gcc/testsuite/ChangeLog

+2011-12-19  Sandra Loosemore  <sandra@codesourcery.com>
+	    Tom de Vries <tom@codesourcery.com>
+
+	PR rtl-opt/50380
+	* gcc.c-torture/compile/pr50380.c: New testcase.
+
 2011-12-19  Tobias Burnus  <burnus@net-b.de>
 
 	PR fortran/51605

gcc/testsuite/gcc.c-torture/compile/pr50380.c

+/* This test used to get stuck in an infinite loop in find_comparison_args
+   when compiling for MIPS at -O2.  */
+
+__attribute__ ((__noreturn__)) extern void fail (void);
+
+char x;
+
+void foo (const unsigned char y)
+{
+   ((void) (__builtin_expect((!! y == y), 1) ? 0 : (fail (), 0)));
+   x = ! y;
+}