[PATCH] Added llvm.is.constant intrinsic

[Renato Golin]

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Comment at: docs/LangRef.rst:7164
@@ +7163,3 @@
+
+This is an overloaded intrinsic. You can use llvm.is.constant on any integer bit width.
+
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As I understand, __builtin_constant_p can be used with any valid expression, and "constant" is the C semantics, so a numeric expression is constant if all its arguments are, string literals are always constant, but pointers are a bit more complicated.

Since this is a GNU extension and we're trying to implement it, it would be wise to add a FIXME and some comments on this documentation to that effect, if our intentions is to not expand to full expresisons, or to do so in the future.

http://reviews.llvm.org/D4276