- RegisterPass<Hello> X("hello", "Hello World Pass");
+ RegisterPass<Hello> X("hello", "Hello World Pass",
+ false /* Only looks at CFG */,
+ false /* Analysis Pass */);
} // end of anonymous namespace
Lastly, we register our class Hello, giving it a command line -argument "hello", and a name "Hello World Pass".
+argument "hello", and a name "Hello World Pass". +Last two RegisterPass arguments are optional. Their default value is false. +If a pass walks CFG without modifying it then third argument is set to true. +If a pass is an analysis pass, for example dominator tree pass, then true +is supplied as fourth argument.As a whole, the .cpp file looks like:
@@ -320,6 +326,7 @@ argument "hello", and a name "Hello World Pass". } }; + char Hello::ID = 0; RegisterPass<Hello> X("hello", "Hello World Pass"); } @@ -995,7 +1002,7 @@ depended on.One of the main responsibilities of the PassManager is the make sure +
One of the main responsibilities of the PassManager is to make sure that passes interact with each other correctly. Because PassManager tries to optimize the execution of passes it must know how the passes interact with each other and what dependencies exist between @@ -1186,7 +1193,7 @@ it is active. For example:
Now that we understand the basics of how passes are defined, how the are +
Now that we understand the basics of how passes are defined, how they are used, and how they are required from other passes, it's time to get a little bit fancier. All of the pass relationships that we have seen so far are very simple: one pass depends on one other specific pass to be run before it can run. @@ -1375,7 +1382,8 @@ the LLVM program representation for a single function at a time, instead of traversing the entire program. It reduces the memory consumption of compiler, because, for example, only one DominatorSet -needs to be calculated at a time. This also makes it possible some interesting enhancements in the future.