fix latest LLVM 11 compatibility issues

[yhls]

• CompositeType class has been removed
• FileLineInfoSpecifier::Default has been renamed to RawValue

@vchuravy

[yhls]

• SequentialType class has been removed
• CreateMemCpy now takes MaybeAligns instead of unsigneds

[vtjnash]

/Users/julia/buildbot/worker/package_macos64/build/src/llvm-late-gc-lowering.cpp:414:1: warning: control may reach end of non-void function [-Wreturn-type]
}
^
1 warning generated.
In file included from /Users/julia/buildbot/worker/package_macos64/build/src/codegen.cpp:853:
./cgutils.cpp:1349:28: warning: variable 'num_elements' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized]
            else if (auto *VT = dyn_cast<VectorType>(T))
                           ^~
./cgutils.cpp:1351:17: note: uninitialized use occurs here
            if (num_elements == 0)
                ^~~~~~~~~~~~
./cgutils.cpp:1349:18: note: remove the 'if' if its condition is always true
            else if (auto *VT = dyn_cast<VectorType>(T))
                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./cgutils.cpp:1346:34: note: initialize the variable 'num_elements' to silence this warning
            uint64_t num_elements;
                                 ^
                                  = 0
1 warning generated.

Need to fix the generated warnings, but otherwise lgtm

[yhls]

I've fixed the warnings, and addressed the following change in LLVM

• deprecated overloads of IRBuilder::CreateCall and CallInst::Create have been removed

by making prepare_call_in in cgutils.cpp return a FunctionCallee instead of a Value*.

[yhls]

• CallSite class has been removed

[vchuravy]

To use getNumElements, I'd have to explicitly cast T to StructType like in the following cases--do you suggest that I do this?

Probably want to use a dyn_cast then.

[yhls]

To use getNumElements, I'd have to explicitly cast T to StructType like in the following cases--do you suggest that I do this?

Probably want to use a dyn_cast then.

I meant to say that using getStructNumElements allows us to avoid having to cast explicitly, as opposed to using getNumElements with a dyn_cast, so is probably preferable. But I'm pretty indifferent about one over the other here.

[vchuravy]

I meant to say that using getStructNumElements allows us to avoid having to cast explicitly, as opposed to using getNumElements with a dyn_cast, so is probably preferable. But I'm pretty indifferent about one over the other here.

It looks like LLVM is removing all the convenience getters, and it is cheaper to do the dyn_cast then to do an isa check and then do the cast inside getStructNumElements (which will do another isa check.)

[yhls]

Ah, ok, changed to use getNumElements.