This makes use of the recently-added @llvm.assume intrinsic to implement a
__builtin_assume(bool) intrinsic (to provide additional information to the
optimizer). This hooks up __assume in MS-compatibility mode to mirror
__builtin_assume (the semantics have been intentionally kept compatible), and
implements GCC's __builtin_assume_aligned as assume((p - o) & mask == 0). LLVM
now contains special logic to deal with assumptions of this form.
llvm-svn: 217349
Clang supports __assume, at least at the semantic level, when MS extensions are
enabled. Unfortunately, trying to actually compile code using __assume would
result in this error:
error: cannot compile this builtin function yet
__assume is an optimizer hint, and can be ignored at the IR level. Until LLVM
supports assumptions at the IR level, a noop lowering is valid, and that is
what is done here.
llvm-svn: 213206