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Add utility function to IRBuilder that takes the difference between two 

pointers, taking into account the size of the pointed-to object.
Patch by Jeffrey Yasskin!

llvm-svn: 68768
This commit is contained in:
Nick Lewycky 2009-04-10 05:30:48 +00:00
parent ffb1fdf25b
commit b0001322e0
1 changed files with 14 additions and 0 deletions
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14
llvm/include/llvm/Support/IRBuilder.h
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@ -681,6 +681,20 @@ public:
Name); Name);
} }
/// CreatePtrDiff - Return the i64 difference between two pointer values,
/// dividing out the size of the pointed-to objects. This is intended to
/// implement C-style pointer subtraction.
Value *CreatePtrDiff(Value *LHS, Value *RHS, const char *Name = "") {
assert(LHS->getType() == RHS->getType() &&
"Pointer subtraction operand types must match!");
const PointerType *ArgType = cast<PointerType>(LHS->getType());
Value *LHS_int = CreatePtrToInt(LHS, Type::Int64Ty);
Value *RHS_int = CreatePtrToInt(RHS, Type::Int64Ty);
Value *Difference = CreateSub(LHS_int, RHS_int);
return CreateSDiv(Difference,
ConstantExpr::getSizeOf(ArgType->getElementType()),
Name);
}
}; };
} }