blocks|key|64151|text|LLVM中的值不需要有名称；实际上，这些基本块没有名称，这就是为什么您从currBB->getName()获得一个空字符串。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|64152|它们在LLVM打印输出中具有名称的原因是，当您打印到LLVM的文本格式(如在.ll文件中显示)时，您必须为它们指定一个名称以使其可引用，因此打印机会将连续的数字名称分配给基本块(和其他值)。但是，这些数字名称仅由打印机创建，并不实际存在于模块中。|64153|entityMap^0|10|H|0|0^^$0|@$1|2|3|4|5|6|7|J|8|@$9|K|A|L|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|M|8|@]|D|@]|E|$]]|$1|H|3|-4|5|6|7|N|8|@]|D|@]|E|$]]]|I|$]]

Values in LLVM IR are not required to have a name; and indeed, those basic blocks don't have names, which is why you get an empty string from <code>currBB-&gt;getName()</code>.

The reason that they have names in the LLVM IR printout is because when you print to the textual format of LLVM IR (as it appears in .ll files), you have to assign a name to them to make them referable, so the printer assigns sequential numeric names to basic blocks (and other values). Those numeric names are only created by the printer, though, and don't actually exist in the module.

blocks|key|4570493|text|虽然BasicBlocks可能没有名称(如hasName()方法所示)，但是可以通过使用currBB->printAsOperand(errs(),+false)来打印唯一的BasicBlock标识符，而不是将currBB->getName()的值流到errs()中。对于未命名的BasicBlock，这将提供数值基本块表示，如%2568。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4570494|entityMap^0|L|9|18|11|2X|H|3I|6|4K|3|0^^$0|@$1|2|3|4|5|6|7|H|8|@$9|I|A|J|B|C]|$9|K|A|L|B|C]|$9|M|A|N|B|C]|$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@]|E|$]]|$1|F|3|-4|5|6|7|S|8|@]|D|@]|E|$]]]|G|$]]

While BasicBlocks may be with no name (as indicated by <code>hasName()</code> method) one may print unique BasicBlock identifier by using <code>currBB-&gt;printAsOperand(errs(), false)</code> instead of streaming into <code>errs()</code> the value of <code>currBB-&gt;getName()</code>. For unnamed BasicBlock this would provide the numerical basic block representation, such as <code>%68</code> .

blocks|key|64197|text|我认为LLVM现在的行为是不同的。我使用类似的代码行，可以在LLVM-4.0上获得标签的名称|type|unstyled|depth|inlineStyleRanges|entityRanges|data|64198|for+(auto+&funct+:+m)+{
++++++++++++for+(auto+&basic_block+:+funct)+{
++++++++++++StringRef+bbName(basic_block.getName());
++++++++++++++++errs()+<<+"BasicBlock:+"++<<+bbName+<<+"\n";
++++++++++++}
}|code-block|syntax|javascript|64199|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I think the behavior of LLVM now is different.
I use similar lines of code and can get the label's name on LLVM-4.0

<pre><code>for (auto &amp;funct : m) {
 for (auto &amp;basic_block : funct) {
 StringRef bbName(basic_block.getName());
 errs() &lt;&lt; "BasicBlock: " &lt;&lt; bbName &lt;&lt; "\n";
 }
}
</code></pre>

blocks|key|4570582|text|正如ElazarR所说，currBB->printAsOperand(errs(),+false)将在错误流中打印这样的ID，但如果您的逻辑对此更感兴趣，也可以将其存储在字符串中。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4570583|在LLVM生成过程中，-dot-cfg总是使用BB的名称(如果有的话)或其字符串表示来命名基本块。此逻辑存在于CFGPrinter.h报头(http://llvm.org/doxygen/CFGPrinter_8h_source.html#l00063)中：|4570584|static+std::string+getSimpleNodeLabel(const+BasicBlock+*Node,
++++++++++++++++++++++++++++++++++++++const+Function+*)+{
++++if+(!Node->getName().empty())
++++++++return+Node->getName().str();

++++std::string+Str;
++++raw_string_ostream+OS(Str);

++++Node->printAsOperand(OS,+false);
++++return+OS.str();
}|code-block|syntax|javascript|4570585|您可以使用此逻辑始终返回基本块的有效名称。|4570586|entityMap|0|LINK|mutability|MUTABLE|url|http://llvm.org/doxygen/CFGPrinter_8h_source.html#l00063^0|C|11|0|B|8|1J|C|1Y|1K|0|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]|$9|12|A|13|B|C]]|D|@$9|14|A|15|1|16]]|E|$]]|$1|H|3|I|5|J|7|17|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|18|8|@]|D|@]|E|$]]|$1|O|3|-4|5|6|7|19|8|@]|D|@]|E|$]]]|P|$Q|$5|R|S|T|E|$U|V]]]]

As ElazarR said, <code>currBB-&gt;printAsOperand(errs(), false)</code> will print such ID in the error stream, but it is possible to store it in a string as well if this is more interesting to your logic.

In the LLVM CFG generation pass <code>-dot-cfg</code>, they always name the basic block using the BB's name (if any) or its representation as a string. This logic is present in the <code>CFGPrinter.h</code> header (<a href="http://llvm.org/doxygen/CFGPrinter_8h_source.html#l00063" rel="nofollow noreferrer">http://llvm.org/doxygen/CFGPrinter_8h_source.html#l00063</a>):

<pre><code>static std::string getSimpleNodeLabel(const BasicBlock *Node,
 const Function *) {
 if (!Node-&gt;getName().empty())
 return Node-&gt;getName().str();

 std::string Str;
 raw_string_ostream OS(Str);

 Node-&gt;printAsOperand(OS, false);
 return OS.str();
}
</code></pre>

You can use this logic to always return a valid name for the basic block.

blocks|key|64261|text|使用clang将源代码编译为bitcode时，请使用以下标志|type|unstyled|depth|inlineStyleRanges|entityRanges|data|64262|-fno-discard-value-names|code-block|syntax|javascript|64263|您将以唯一字符串的形式获得基本块的名称|64264|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

While compiling source code to bitcode using clang use the below flag
<pre><code>-fno-discard-value-names
</code></pre>
You will get the name of basic block as a unique string

I have written a pass to detect and print the label of basicblocks in a function, for I want to use <code>splitBasicBlock()</code> further. I wrote that like this:

<pre><code>virtual bool runOnModule(Module &amp;M)
{
 for(Module::iterator F = M.begin(), E = M.end(); F!= E; ++F)
 {
 errs()&lt;&lt;"Function:"&lt;&lt;F-&gt;getName()&lt;&lt;"\n";
 //for(Function::iterator BB = F-&gt;begin(), E = F-&gt;end(); BB != E; ++BB)
 for (iplist&lt;BasicBlock&gt;::iterator iter = F-&gt;getBasicBlockList().begin();
 iter != F-&gt;getBasicBlockList().end();
 iter++)
 {
 BasicBlock* currBB = iter;
 errs() &lt;&lt; "BasicBlock: " &lt;&lt; currBB-&gt;getName() &lt;&lt; "\n"; 
 }
 }
 return true;
}
</code></pre>

IR file looks like this:

<pre><code>; &lt;label&gt;:63 ; preds = %43
 %64 = load i32* %j, align 4
 %65 = sext i32 %64 to i64
 %66 = load i8** %tempdst, align 8
 %67 = getelementptr inbounds i8* %66, i64 %65
 store i8 -1, i8* %67, align 1
 br label %73

; &lt;label&gt;:68 ; preds = %43
 %69 = load i32* %j, align 4
 %70 = sext i32 %69 to i64
 %71 = load i8** %tempdst, align 8
 %72 = getelementptr inbounds i8* %71, i64 %70
 store i8 0, i8* %72, align 1
 br label %73

; &lt;label&gt;:73 ; preds = %68, %63
 br label %74
</code></pre>

However, I got nothing about the label:

<pre><code>Function:main
BasicBlock:
BasicBlock:
BasicBlock:
</code></pre>

What's wrong with these "unnamed" basic block? What should I do?

llvm: How to get the label of Basic Blocks

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我已经写了一个pass来检测和打印函数中基本块的标签，因为我想进一步使用splitBasicBlock()。我是这样写的：virtual bool runOnModule(Module &M){    for(Module::iterator F = M.begin(), E = M.end(); F!= E; ++F...

问llvm:如何获取基本块的标签
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问llvm:如何获取基本块的标签
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