Fix non-canonical CONST_INTs in altivec_copysign_v4sf3 (PR91823)

The pattern was generating zero-extended rather than sign-extended
CONST_INTs.

2019-09-23  Richard Sandiford  <richard.sandiford@arm.com>

gcc/
	PR target/91823
	* config/rs6000/altivec.md (altivec_copysign_v4sf3): Generate
	canonical CONST_INTs.  Use gen_rtvec.

From-SVN: r276055

gcc/ChangeLog

+2019-09-23  Richard Sandiford  <richard.sandiford@arm.com>
+
+	PR target/91823
+	* config/rs6000/altivec.md (altivec_copysign_v4sf3): Generate
+	canonical CONST_INTs.  Use gen_rtvec.
+
 2019-09-23  Richard Biener  <rguenther@suse.de>
 
 	* tree-vect-loop.c (get_initial_def_for_reduction): Simplify,

gcc/config/rs6000/altivec.md

@@ -2198,13 +2198,8 @@
   "VECTOR_UNIT_ALTIVEC_P (V4SFmode)"
 {
   rtx mask = gen_reg_rtx (V4SImode);
-  rtvec v = rtvec_alloc (4);
-  unsigned HOST_WIDE_INT mask_val = ((unsigned HOST_WIDE_INT)1) << 31;
-
-  RTVEC_ELT (v, 0) = GEN_INT (mask_val);
-  RTVEC_ELT (v, 1) = GEN_INT (mask_val);
-  RTVEC_ELT (v, 2) = GEN_INT (mask_val);
-  RTVEC_ELT (v, 3) = GEN_INT (mask_val);
+  rtx mask_val = gen_int_mode (HOST_WIDE_INT_1U << 31, SImode);
+  rtvec v = gen_rtvec (4, mask_val, mask_val, mask_val, mask_val);
 
   emit_insn (gen_vec_initv4sisi (mask, gen_rtx_PARALLEL (V4SImode, v)));
   emit_insn (gen_vector_select_v4sf (operands[0], operands[1], operands[2],