[COMMITTED] Fix PR aarch64/104474: ICE with vector float initializers and non-consts.

The problem here is that the aarch64 back-end was placing const0_rtx
into the constant vector RTL even if the mode was a floating point mode.
The fix is instead to use CONST0_RTX and pass the mode to select the
correct zero (either const_int or const_double).

Committed as obvious after a bootstrap/test on aarch64-linux-gnu with
no regressions.

	PR target/104474

gcc/ChangeLog:

	* config/aarch64/aarch64.cc
	(aarch64_sve_expand_vector_init_handle_trailing_constants):
	Use CONST0_RTX instead of const0_rtx for the non-constant elements.

gcc/testsuite/ChangeLog:

	* gcc.target/aarch64/sve/pr104474-1.c: New test.
	* gcc.target/aarch64/sve/pr104474-2.c: New test.
	* gcc.target/aarch64/sve/pr104474-3.c: New test.

Author: apinski-cavium

gcc/config/aarch64/aarch64.cc

@@ -21164,7 +21164,7 @@ aarch64_sve_expand_vector_init_handle_trailing_constants
 	{
 	  rtx x = builder.elt (i + nelts_reqd - n_trailing_constants);
 	  if (!valid_for_const_vector_p (elem_mode, x))
-	    x = const0_rtx;
+	    x = CONST0_RTX (elem_mode);
 	  v.quick_push (x);
 	}
       rtx const_vec = v.build ();

gcc/testsuite/gcc.target/aarch64/sve/pr104474-1.c

@@ -0,0 +1,9 @@
+/* { dg-options "-mcpu=neoverse-512tvb -frounding-math -msve-vector-bits=512" } */
+
+typedef float __attribute__((__vector_size__ (64))) F;
+
+F
+foo (void)
+{
+  return (F){68435453, 0, 0, 0, 0, 0, 0, 5, 0, 431144844};
+}

gcc/testsuite/gcc.target/aarch64/sve/pr104474-2.c

@@ -0,0 +1,9 @@
+/* { dg-options "-mcpu=neoverse-512tvb -msve-vector-bits=512" } */
+
+typedef float __attribute__((__vector_size__ (64))) F;
+
+F
+foo (float t)
+{
+  return (F){t, 0, 0, 0, 0, 0, 0, 5, 0, t};
+}

gcc/testsuite/gcc.target/aarch64/sve/pr104474-3.c

@@ -0,0 +1,9 @@
+/* { dg-options "-mcpu=neoverse-v1 -frounding-math -msve-vector-bits=256" } */
+
+typedef _Float16 __attribute__((__vector_size__ (32))) F;
+
+F
+foo (void)
+{
+  return (F){0, 6270, 0, 0, 0, 0, 0, 0, 3229, 0, 40};
+}