[AArch64] Fix label mode

This patch fixes a case where we tried to force a VOIDmode label
into a DImode register, which led to invalid rtl that was previously
undiagnosed.

2017-08-22  Richard Sandiford  <richard.sandiford@linaro.org>
	    Alan Hayward  <alan.hayward@arm.com>
	    David Sherwood  <david.sherwood@arm.com>

gcc/
	* config/aarch64/aarch64.md (casesi): Use DImode rather than
	VOIDmode for the LABEL_REF.

Co-Authored-By: Alan Hayward <alan.hayward@arm.com>
Co-Authored-By: David Sherwood <david.sherwood@arm.com>

From-SVN: r251266

gcc/ChangeLog

+2017-08-22  Richard Sandiford  <richard.sandiford@linaro.org>
+	    Alan Hayward  <alan.hayward@arm.com>
+	    David Sherwood  <david.sherwood@arm.com>
+
+	* config/aarch64/aarch64.md (casesi): Use DImode rather than
+	VOIDmode for the LABEL_REF.
+
 2017-08-22  Richard Biener  <rguenther@suse.de>
 
 	* tree-cfg.c (gimple_split_edge): Avoid reallocating target

gcc/config/aarch64/aarch64.md

@@ -495,7 +495,7 @@
 						 const0_rtx),
 				    operands[0], operands[2], operands[4]));
 
-    operands[2] = force_reg (DImode, gen_rtx_LABEL_REF (VOIDmode, operands[3]));
+    operands[2] = force_reg (DImode, gen_rtx_LABEL_REF (DImode, operands[3]));
     emit_jump_insn (gen_casesi_dispatch (operands[2], operands[0],
 					 operands[3]));
     DONE;