preserving执行管线 [英] Preserving the Execution pipeline

问题描述

返回类型经常检查是否存在错误。但是，在code，将继续执行可以以不同的方式来指定。

 如果（！RET）
{
   doNoError code（）;
}
出口（1）;
 

或

 如果（RET）
{
   出口（1）;
}
doNoError code（）;
 

单向重量级的CPU可以推测使用简单的统计靠近接近/地区所采取的分支 - 我研究了分支预测的4位机制（-2，-1,0，+ 1，+ 2）其中零为未知和2将被认为是一个真正的分支。

考虑到上述简单的技术，我的问题是关于如何构造code。我认为必须有重大的编译器和重大架构之间的约定。这是我的两个问题。

1. 当code不是它的布尔值偏向当管道被填充为经常访问的循环？


2. 猜测分支必须在真或假或零（管道必须填写的东西）开头。这是它可能是？

解决方案

行为的CPU的不同而不同，编译器经常重新排序的说明。
你会发现你在这些手册需要的所有信息。 http://agner.org/optimize/

在我看来就知道发生什么事的唯一途径是阅读由编译器生成的汇编code。

Return types are frequently checked for errors. But, the code that will continue to execute may be specified in different ways.

if(!ret)
{
   doNoErrorCode();
}
exit(1);

or

if(ret)
{
   exit(1);
}
doNoErrorCode();

One way heavyweight CPU's can speculate about the branches taken in near proximity/locality using simple statistics - I studied a 4-bit mechanism for branch speculation (-2,-1,0,+1,+2) where zero is unknown and 2 will be considered a true branch.

Considering the simple technique above, my questions are about how to structure code. I assume that there must be a convention among major compilers and major architectures. These are my two questions

1. When the code isn't an often-visited loop which boolean value is biased for when the pipeline is being filled ?
2. Speculation about branching must begin at either true or false or zero ( the pipeline must be filled with something). Which is it likely to be ?

解决方案

The behavior varies among CPUs, and the compiler often reorders instructions. You will find all the information you need in these manuals: http://agner.org/optimize/.

In my opinion the only way to know what happens is to read the assembly code generated by the compiler.

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