tcg: Improve call argument loading

Free the argument register only after we have verified that the
temporary is not already in that register.  This case is likely
now that we are back propagating the preferred register.
Signed-off-by: NRichard Henderson <richard.henderson@linaro.org>

tcg/tcg.c

@@ -3611,15 +3611,16 @@ static void tcg_reg_alloc_call(TCGContext *s, TCGOp *op)
         if (arg != TCG_CALL_DUMMY_ARG) {
             ts = arg_temp(arg);
             reg = tcg_target_call_iarg_regs[i];
-            tcg_reg_free(s, reg, allocated_regs);
 
             if (ts->val_type == TEMP_VAL_REG) {
                 if (ts->reg != reg) {
+                    tcg_reg_free(s, reg, allocated_regs);
                     tcg_out_mov(s, ts->type, reg, ts->reg);
                 }
             } else {
                 TCGRegSet arg_set = 0;
 
+                tcg_reg_free(s, reg, allocated_regs);
                 tcg_regset_set_reg(arg_set, reg);
                 temp_load(s, ts, arg_set, allocated_regs, 0);
             }