[PATCH] D26196: Add support for non-zero null pointers

[Yaxun Liu via cfe-commits]

yaxunl added inline comments.


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Comment at: lib/CodeGen/CodeGenTypes.cpp:743
+    auto NullPtr = CGM.getNullPtr(LLPT, T);
+    return isa<llvm::ConstantPointerNull>(NullPtr);
+  }
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tony-tye wrote:
> Is this correct if the target does not represent a NULL pointer as the address with value 0? Or should this be asking the target if this null pointer is represented by an address value of 0?
Currently this is correct even if the target does not represent a null pointer as address with value 0. The purpose of this line is to check if NullPtr has zero value at compile time. In LLVM checking whether a pointer having zero value at compile time is by checking if it is ConstantPointerNull.

However, if in the future LLVM no longer assumes ConstantPointerNull having zero value, then this will become incorrect. To be future proof, I think I'd better add a member function isPtrZero to TargetCodeGenInfo and use it to check if a pointer has zero value.


https://reviews.llvm.org/D26196