[TableGen] Add more checks to the subtarget emitter to validate scheduling information.

[llvmbot]

Bugzilla Link	37310
Version	unspecified
OS	Linux
Blocks	#31672 #34991
Reporter	LLVM Bugzilla Contributor
CC	@adibiagio,@topperc,@filcab,@gregbedwell,@RKSimon

Extended Description

Some scheduling information makes no sense but makes it through the SubtargetEmitter without any warnings. We should add more validation.
Stuff that makes absolutely no sense should trigger fatal errors.

One example I stumbled upon is inconsistencies in resource units vs resource cycles: The cycles are optional and default to all ones, opening up to various miserpretations by the developers that are not caught at compile time. This happens at least on Arm/AArch64 and X86.

[llvmbot]

https://reviews.llvm.org/D46356

[thanm]

*** Bug #18016 has been marked as a duplicate of this bug. ***