aarch64: Fix BE SVE mode punning involving floats

The patterns used by aarch64_split_sve_subreg_move only support
integer modes, so if the widest mode is a float, we should get
its integer equivalent.

Fixes gcc.target/aarch64/sel_3.c for big-endian targets.

2020-01-16  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	* config/aarch64/aarch64.c (aarch64_split_sve_subreg_move): Apply
	aarch64_sve_int_mode to each mode.

gcc/ChangeLog

+2020-01-16  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* config/aarch64/aarch64.c (aarch64_split_sve_subreg_move): Apply
+	aarch64_sve_int_mode to each mode.
+
 2020-01-15  David Malcolm  <dmalcolm@redhat.com>
 
 	* doc/analyzer.texi (Overview): Add note about

gcc/config/aarch64/aarch64.c

@@ -4827,8 +4827,8 @@ aarch64_split_sve_subreg_move (rtx dest, rtx ptrue, rtx src)
   /* Decide which REV operation we need.  The mode with wider elements
      determines the mode of the operands and the mode with the narrower
      elements determines the reverse width.  */
-  machine_mode mode_with_wider_elts = GET_MODE (dest);
-  machine_mode mode_with_narrower_elts = GET_MODE (src);
+  machine_mode mode_with_wider_elts = aarch64_sve_int_mode (GET_MODE (dest));
+  machine_mode mode_with_narrower_elts = aarch64_sve_int_mode (GET_MODE (src));
   if (GET_MODE_UNIT_SIZE (mode_with_wider_elts)
       < GET_MODE_UNIT_SIZE (mode_with_narrower_elts))
     std::swap (mode_with_wider_elts, mode_with_narrower_elts);