ac/nir: implement half-float nir_op_frsq

v2: don't use ac_get_onef()

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>

src/amd/common/ac_nir_to_llvm.c

@@ -788,8 +788,7 @@ static void visit_alu(struct ac_nir_context *ctx, const nir_alu_instr *instr)
 	case nir_op_frsq:
 		result = emit_intrin_1f_param(&ctx->ac, "llvm.sqrt",
 		                              ac_to_float_type(&ctx->ac, def_type), src[0]);
-		result = ac_build_fdiv(&ctx->ac, instr->dest.dest.ssa.bit_size == 32 ? ctx->ac.f32_1 : ctx->ac.f64_1,
-				       result);
+		result = ac_build_fdiv(&ctx->ac, LLVMConstReal(LLVMTypeOf(result), 1.0), result);
 		break;
 	case nir_op_frexp_exp:
 		src[0] = ac_to_float(&ctx->ac, src[0]);