[hellogcc] Re: gccint-zh ch13.4 and ch13.5
- From: 陳韋任 <chenwj@xxxxxxxxxxxxxx>
- To: hellogcc@xxxxxxxxxxxxx
- Date: Wed, 15 Feb 2012 20:50:50 +0800
[...]
> +@en All statements that may define memory have exactly one accompanied
> +@en definition of a virtual SSA name using the previous state of memory
> +@en and defining the new state of memory after the given point in the IL.
> +
> +如果一个指令可能向内存中写数据，那么这个指令就对应一个虚拟SSA name的定
> 义，在IL中的给定点之前保持内存的先前状态，在该给定点之后被赋予新的值。
以上大致沒問題。我好奇的是 IL 是代表 intermediate language 嗎?
> +
> @smallexample
> int i;
> int foo (void)
> @@ -1099,73 +1105,103 @@
> @}
> @end smallexample
>
> -The virtual SSA names in this case are @code{.MEM_2(D)} and
> -@code{.MEM_3}. The store to the global variable @code{i}
> -defines @code{.MEM_3} invalidating @code{.MEM_2(D)}. The
> -load from @code{i} uses that new state @code{.MEM_3}.
> +@en The virtual SSA names in this case are @code{.MEM_2(D)} and
> +@en @code{.MEM_3}. The store to the global variable @code{i}
> +@en defines @code{.MEM_3} invalidating @code{.MEM_2(D)}. The
> +@en load from @code{i} uses that new state @code{.MEM_3}.
>
> -The virtual SSA web serves as constraints to SSA optimizers
> -preventing illegitimate code-motion and optimization. It
> -also provides a way to walk related memory statements.
> +在这个例子中，vitrual SSA name分别是@code{.MEM_2(D)}和@code{.MEM_3}。全
> 局变量@code{i}对应的存储区定义了 @code{.MEM_3}，同时使@code{.MEM_2(D)}无
> 效。（此后）从@code{i}加载使用的就是新状态 @code{.MEM_3}。
>
> +@en The virtual SSA web serves as constraints to SSA optimizers
> +@en preventing illegitimate code-motion and optimization. It
> +@en also provides a way to walk related memory statements.
^^^^^^^^^^^^^^^^^^^^^^^^^
> +Virtual SSA web 用于对SSA相关优化的约束，防止不合法的代码移动和优化。同
> 时也可以用来遍历相关的指令。
^^^^^^^^^^
相關存取內存的指令，如何?
> @item Points-to and escape analysis.
>
> -Points-to analysis builds a set of constraints from the GIMPLE
> -SSA IL representing all pointer operations and facts we do
> -or do not know about pointers. Solving this set of constraints
> -yields a conservatively correct solution for each pointer
> -variable in the program (though we are only interested in
> -SSA name pointers) as to what it may possibly point to.
> +@item 指向分析和逃逸分析
>
> -This points-to solution for a given SSA name pointer is stored
> -in the @code{pt_solution} sub-structure of the
> -@code{SSA_NAME_PTR_INFO} record. The following accessor
> -functions are available:
> +@en Points-to analysis builds a set of constraints from the GIMPLE
> +@en SSA IL representing all pointer operations and facts we do
> +@en or do not know about pointers. Solving this set of constraints
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> +@en yields a conservatively correct solution for each pointer
> +@en variable in the program (though we are only interested in
> +@en SSA name pointers) as to what it may possibly point to.
>
> +指向分析从GIMPLE SSA IL中提取有关指针的信息，建立一个包含所有指针的约束
> 集合。对约束集合的求解得到一个保守但是正确的解，计算出程序中的每一个指针
> 变量（虽然我们只对 SSA name指针感兴趣）可能指向的位置。
我可能太吹毛求疵了。"and facts ..." 是刻意沒翻亦或是漏掉?
[...]
> +@en @code{walk_non_aliased_vuses} walks over dominating memory defining
^^^^^^^^^^^^^^^^^^^^^^^^^^
> +@en statements and calls back if the statement does not clobber ref
> +@en providing the non-aliased VUSE. The walk stops at
> +@en the first clobbering statement or if asked to.
> +
> +@code{walk_non_aliased_vuses}遍历所有支配的内存定义指令（dominating
> memory defining statements），根据non-aliased VUSE判断指令是否破坏了
> （clobber）ref。当遍历的指令没有破坏ref时进行回调（call back）。遍历在被
> （调用者）要求时或遇见第一个破坏了ref的指令时停止。
編譯器裡面有所謂的 Dominator。這裡的 dominating 概念上跟 Dominator 一樣嗎?
> +@en @code{walk_aliased_vdefs} walks over dominating memory defining
> +@en statements and calls back on each statement clobbering ref
> +@en providing its aliasing VDEF. The walk stops if asked to.
> +
> +@code{walk_aliased_vdefs}遍历所有支配的内存定义指令，当遇到破坏了
> （clobber）ref的指令时进行回调（根 据它的aliasing VDEF进行判断）。遍历在
> 被（调用者）要求时停止。
> @@ -1173,26 +1209,36 @@
> @section Memory model
> @cindex memory model
^^^^^^^^^^^^
內存模型?
[...]
--
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj
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