[llvm-commits] add nounwind flag to BasicBlock

[Nick Lewycky]

This adds the nounwind flag (as seen on CallInst and Function) to basic 
blocks.

Why not just leave the unwind-dest null? That could mean one of two 
things, either that an unwind should propagate up or that the basic 
block will never unwind. In the second case, simplifycfg could merge it 
with another BB that has an 'unwinds to', but in the first case merging 
them would change the actual behaviour of the code.

Like the nounwind flag on call and functions, this flag can be computed 
by looking at the instructions inside the block, we just don't want to 
do that computation every time. This just memoizes that analysis for 
other consumers.

Please review this patch.

Nick
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