归纳变量分析结果

[Jianzhang Peng]

Internal里面对归纳变量的分析结果描述

The description of the induction variable is provided in struct
rtx_iv. In order to handle subregs, the representation is a bit
complicated; if the value of the extend field is not UNKNOWN, the
value of the induction variable in the i-th iteration is

delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)),

with the following exception: if first_special is true, then the value
in the first iteration (when i is zero) is delta + mult * base.
However, if extend is equal to UNKNOWN, then first_special must be
false, delta 0, mult 1 and the value in the i-th iteration is

subreg_{mode} (base + i * step)

The function get_iv_value can be used to perform these calculations.

==============
其中公式
delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)),
中 extend extend_mode, subreg, subreg_mode是什么意思?

谢谢
--
Jianzhang Peng

[Eric Fisher]

> 其中公式
> delta + mult * extend_{extend_mode} (subreg_{mode} (base + i * step)),
> 中 extend extend_mode, subreg, subreg_mode是什么意思?

比如32位的寄存器reg，可能会作为16位子寄存器来使用，即subreg，它的机器模式就是subreg_mode。

反过来，如果将16位的整数，算术（或逻辑）扩展为32位，成为extend，扩展后的机器模式为extend_mode。

2009/12/18 Jianzhang Peng <pengji...@gmail.com>:

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[Jianzhang Peng]

谢谢

2009/12/21 Eric Fisher <joefo...@gmail.com>:

--
Jianzhang Peng