[Mlir-commits] [mlir] [mlir][ptr] Add `ptr.ptr_diff` operation (PR #157354)

[Fabian Mora]

================
@@ -415,6 +415,63 @@ def Ptr_PtrAddOp : Pointer_Op<"ptr_add", [
   }];
 }
 
+//===----------------------------------------------------------------------===//
+// PtrDiffOp
+//===----------------------------------------------------------------------===//
+
+def Ptr_PtrDiffOp : Pointer_Op<"ptr_diff", [
+    Pure, AllTypesMatch<["lhs", "rhs"]>, SameOperandsAndResultShape
+  ]> {
+  let summary = "Pointer difference operation";
+  let description = [{
+    The `ptr_diff` operation computes the difference between two pointers,
+    returning an integer or index value representing the number of bytes
+    between them. This difference is always computed using signed arithmetic.
----------------
fabianmcg wrote:

Negative pointers no, but take: (ptr + 16) - (ptr + 32), the result will be negative.

I took as rationale the existence of `ptrdiff_t` in C https://en.cppreference.com/w/c/types/ptrdiff_t.html

I'll clarify the comment.

https://github.com/llvm/llvm-project/pull/157354