re PR target/84700 (ICE on 32-bit BE powerpc targets w/ -misel -O1)

	PR target/84700
	* combine.c (combine_simplify_rtx): Don't try to simplify if
	if_then_else_cond returned non-NULL, but either true_rtx or false_rtx
	are equal to x.

	* gcc.target/powerpc/pr84700.c: New test.

From-SVN: r258263

gcc/ChangeLog

+2018-03-05  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/84700
+	* combine.c (combine_simplify_rtx): Don't try to simplify if
+	if_then_else_cond returned non-NULL, but either true_rtx or false_rtx
+	are equal to x.
+
 2018-03-05  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* config/rs6000/rs6000.c (rs6000_loop_align): Don't align tiny loops

gcc/combine.c

@@ -5734,7 +5734,11 @@ combine_simplify_rtx (rtx x, machine_mode op0_mode, int in_dest,
 	  /* If everything is a comparison, what we have is highly unlikely
 	     to be simpler, so don't use it.  */
 	  && ! (COMPARISON_P (x)
-		&& (COMPARISON_P (true_rtx) || COMPARISON_P (false_rtx))))
+		&& (COMPARISON_P (true_rtx) || COMPARISON_P (false_rtx)))
+	  /* Similarly, if we end up with one of the expressions the same
+	     as the original, it is certainly not simpler.  */
+	  && ! rtx_equal_p (x, true_rtx)
+	  && ! rtx_equal_p (x, false_rtx))
 	{
 	  rtx cop1 = const0_rtx;
 	  enum rtx_code cond_code = simplify_comparison (NE, &cond, &cop1);

gcc/testsuite/ChangeLog

+2018-03-05  Jakub Jelinek  <jakub@redhat.com>
+
+	PR target/84700
+	* gcc.target/powerpc/pr84700.c: New test.
+
 2018-03-05  Nathan Sidwell  <nathan@acm.org>
 
 	PR c++/84702

gcc/testsuite/gcc.target/powerpc/pr84700.c

+/* PR target/84700 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -misel" } */
+
+long long int
+foo (long long int x)
+{
+  long long int a = x < 2;
+  int b = a >= 0;
+
+  return a + ((x == 0) ? a : b);
+}