[PATCH] Added llvm.is.constant intrinsic

[Renato Golin]

Thanks Janusz,

I'm adding Owen to review this patch, since it's not my area, but overall, the patch looks good.

About the tests, though the inline check is important, I was thinking something more elaborate.

Some examples that come to mind:

* static initializer
* generic function arguments
* function arguments where the function is static and only called one with a constant argument
* function arguments where the function is static and only called one with a variable argument
* expressions that will be simplified as constant because all variables were initialised with constants
* expressions that will NOT be simplified as constant because NOT all variables were initialised with constants

Those examples that *should* be constant and are not, should be marked as FIXME. Those examples that *should* NOT be constant and are, should be fixed before commit.

cheers,
--renato

================
Comment at: test/CodeGen/Generic/inline-is-constant.ll:4
@@ +3,3 @@
+; Expected outcome: @fun is inlined and @llvm.is.constant is resolved to TRUE
+; Without inlining @llvm.is.constant would resolve to FALSE.
+
----------------
a more robust way would be to have two run lines, one with O0, another with O3, and use FileCheck for the True/False results.

http://reviews.llvm.org/D4276