Verifier: Don't reject varargs callee cleanup functions

We've rejected these kinds of functions since r28405 in 2006 because
it's impossible to lower the return of a callee cleanup varargs
function. However there are lots of legal ways to leave such a function
without returning, such as aborting. Today we can leave a function with
a musttail call to another function with the correct prototype, and
everything works out.

I'm removing the verifier check declaring that a normal return from such
a function is UB.

Reviewed By: nlewycky

Differential Revision: http://reviews.llvm.org/D5059

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216779 91177308-0d34-0410-b5e6-96231b3b80d8
musttail: Forward regparms of variadic functions on x86_64

Summary:
If a variadic function body contains a musttail call, then we copy all
of the remaining register parameters into virtual registers in the
function prologue. We track the virtual registers through the function
body, and add them as additional registers to pass to the call. Because
this is all done in virtual registers, the register allocator usually
gives us good code. If the function does a call, however, it will have
to spill and reload all argument registers (ew).

Forwarding regparms on x86_32 is not implemented because most compilers
don't support varargs in 32-bit with regparms.

Reviewers: majnemer

Subscribers: aemerson, llvm-commits

Differential Revision: http://reviews.llvm.org/D5060

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216780 91177308-0d34-0410-b5e6-96231b3b80d8
Add a const and munge some comments

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216781 91177308-0d34-0410-b5e6-96231b3b80d8
Fix typos in comments, NFC

Summary: Just fixing comments, no functional change.

Test Plan: N/A

Reviewers: jfb

Subscribers: mcrosier, llvm-commits

Differential Revision: http://reviews.llvm.org/D5130

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216784 91177308-0d34-0410-b5e6-96231b3b80d8
Stuff

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216787 91177308-0d34-0410-b5e6-96231b3b80d8
Omit dwarf::DW_AT_frame_base under -gmlt

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216788 91177308-0d34-0410-b5e6-96231b3b80d8
Omit DW_AT_artificial, DW_AT_external, and similar attributes under -gmlt

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216789 91177308-0d34-0410-b5e6-96231b3b80d8
Add a trivial functor for use with unique_ptrs managing memory that needs to be freed rather than deleted.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216790 91177308-0d34-0410-b5e6-96231b3b80d8
Revert accidentally committed patches r216787-r216789

Rushed when I realized I hadn't committed the FreeDeleter for a clang
change I'd committed, and didn't check that I had things lying around in
my client.

Apologies for the noise.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216792 91177308-0d34-0410-b5e6-96231b3b80d8
Speculative build fix for const, gcc, and ArrayRef overloads

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216793 91177308-0d34-0410-b5e6-96231b3b80d8
AArch64: Silence -Wabsolute-value warning with std::abs

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216794 91177308-0d34-0410-b5e6-96231b3b80d8