combine: Use correct mode in new comparison (PR86902)

This code in try_combine uses the wrong mode.  This fails (with RTL
checking) in trunk, but not in any released branches.


	PR rtl-optimization/86902
	* combine.c (try_combine): When changing the CC mode used, don't change
	an unrelated mode in other_insn to that new CC mode.

From-SVN: r264426

gcc/ChangeLog

+2018-09-19  Segher Boessenkool  <segher@kernel.crashing.org>
+
+	PR rtl-optimization/86902
+	* combine.c (try_combine): When changing the CC mode used, don't change
+	an unrelated mode in other_insn to that new CC mode.
+
 2018-09-19  David Malcolm  <dmalcolm@redhat.com>
 
 	* tree-data-ref.c (runtime_alias_check_p): Use formatted printing

gcc/combine.c

@@ -3310,7 +3310,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
 		{
 		  /* Replace cc_use_loc with entire new RTX.  */
 		  SUBST (*cc_use_loc,
-			 gen_rtx_fmt_ee (compare_code, compare_mode,
+			 gen_rtx_fmt_ee (compare_code, GET_MODE (*cc_use_loc),
 					 newpat_dest, const0_rtx));
 		  undobuf.other_insn = cc_use_insn;
 		}
@@ -3319,7 +3319,7 @@ try_combine (rtx_insn *i3, rtx_insn *i2, rtx_insn *i1, rtx_insn *i0,
 		  /* Just replace the CC reg with a new mode.  */
 		  SUBST (XEXP (*cc_use_loc, 0), newpat_dest);
 		  undobuf.other_insn = cc_use_insn;
-		}	      
+		}
 	    }
 
 	  /* Now we modify the current newpat: