[PATCH] D27990: [Thumb] Add support for tMUL in the compare instruction peephole optimizer

[Diana Picus via Phabricator via llvm-commits]

rovka added a comment.

Right, sorry, I was thinking about Thumb2, where MOV doesn't touch the flags.

I guess reordering isn't so bad in this case, but it will affect the registers that you have available. Before, if the operands for tMUL weren't needed elsewhere you could reuse their registers for the constants, now you might need extra regs for them. E.g. in the first example from the test, you end up using up to r3 instead of just up to r2. I think it would be useful to run some benchmarks with this change, to make sure we're not causing trouble in more complicated cases.

Thanks.


https://reviews.llvm.org/D27990