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Pietro Fezzardi
67523ec115
The current implementation DLA cannot reason about function pointers, because function types have zero size. Given this shortcoming, llvm::Functions are used (as a hack) to represent their Functions' return types. This representation is a key factor of how DLA is able to piece information together interprocedurally. This hack has consequences. Assume we're setting up the DLA graph, and we're looking at a use of an llvm::Function that is inside the body of an llvm::Function and is not the callee-operand of a Call. That use is obviously function-pointer typed. But if we try to create a LayoutTypeSystemNode for the llvm::Value of the used llvm::Function, the inner machinery of how the DLA graph is set up will treat is as the return type of the function, which is obviously wrong. So we have to prevent that creation at all costs. Basically creation of LayoutTypeSystemNodes in the DLA graph associated with llvm::Functions are valid only for representing return types. This shortcoming does not affect the power of DLA. In its current form, it doesn't represent function types at all. The problem is that until we undo this hack we will not be able to properly support function types in DLA. This will have to be fixed in the future. In the meantime, this commit provides an helper function to centralize how we detect the offending uses of llvm::Functions. In this way, all the points of the codebase that are affected by this hack are clearly marked.