Currently Clang does not add mustprogress to inifinite loops with a
known constant condition, matching C11 behavior. The forward progress
guarantee in C++11 and later should allow us to add mustprogress to any
loop (http://eel.is/c++draft/intro.progress#1).
This allows us to simplify the code dealing with adding mustprogress a
bit.
Reviewed By: aaron.ballman, lebedev.ri
Differential Revision: https://reviews.llvm.org/D96418
This patch adds 2 new options to control when Clang adds `mustprogress`:
1. -ffinite-loops: assume all loops are finite; mustprogress is added
to all loops, regardless of the selected language standard.
2. -fno-finite-loops: assume no loop is finite; mustprogress is not
added to any loop or function. We could add mustprogress to
functions without loops, but we would have to detect that in Clang,
which is probably not worth it.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D96419
Florian Hahn