intel/compiler: split float to 64-bit opcodes from int to 64-bit

Going forward having these split is a bit more convenient since these two
groups have different restrictions.

v2:
 - Rebased on top of new regioning lowering pass.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com> (v1)
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/intel/compiler/brw_fs_nir.cpp

@@ -907,10 +907,17 @@ fs_visitor::nir_emit_alu(const fs_builder &bld, nir_alu_instr *instr)
    case nir_op_f2f64:
    case nir_op_f2i64:
    case nir_op_f2u64:
+      assert(type_sz(op[0].type) > 2); /* brw_nir_lower_conversions */
+      inst = bld.MOV(result, op[0]);
+      inst->saturate = instr->dest.saturate;
+      break;
+
    case nir_op_i2f64:
    case nir_op_i2i64:
    case nir_op_u2f64:
    case nir_op_u2u64:
+      assert(type_sz(op[0].type) > 1); /* brw_nir_lower_conversions */
+      /* fallthrough */
    case nir_op_f2f32:
    case nir_op_f2i32:
    case nir_op_f2u32: