Hello all,
I am trying to get LLVM to optimize an indirect call to a branching control flow with a direct call and an indirect call.
What I mean is, transform this:
%funcptr = select i1 %condition, void()* @known_function, void ()* %loaded_address
%result = tail call void %funcptr()
into this:
br i1 %condition, label %if.true, label %if.false
if.true:
tail call void @ known_function()
br label %if.end
if.false:
tail call void %loaded_address()
br label %if.end
if.end:
Can LLVM do this perhaps when I add metadata about probabilities of %condition being true or not, or is this not possible at all?
(The reason for my question is a virtual call optimization after profiling. @known_function is simple and inlinable, which I think results in a faster code path when %condition is almost always true. It is very similar to the Indirect Call Promotion currently being implemented as PGO option.)
Thanks,
Johan