[PATCH] Implement __builtin_stack_pointer

[Tim Northover]

  Hi Renato,

  The code changes look innocuous enough, but I think the documentation may be a bit over-enthusiastic in its guarantees:


================
Comment at: docs/LangRef.rst:6802-6803
@@ +6801,4 @@
+
+The '``llvm.stackpointer``' intrinsic returns the current value of the
+stack pointer register.
+
----------------
Isn't that a bit strong? I think things like VLAs can cause sp to change in the middle of a function and I dread to think what it'll return in those cases.


http://llvm-reviews.chandlerc.com/D3184