forked from OSchip/llvm-project
e7e9c04ddf
pool data being loaded into a vector register. The comments take the form of: # ymm0 = [a,b,c,d,...] # xmm1 = <x,y,z...> The []s are used for generic sequential data and the <>s are used for specifically ConstantVector loads. Undef elements are printed as the letter 'u', integers in decimal, and floating point values as floating point values. Suggestions on improving the formatting or other aspects of the display are very welcome. My primary use case for this is to be able to FileCheck test masks passed to vector shuffle instructions in-register. It isn't fantastic for that (no decoding special zeroing semantics or other tricks), but it at least puts the mask onto an instruction line that could reasonably be checked. I've updated many of the new vector shuffle lowering tests to leverage this in their test cases so that we're actually checking the shuffle masks remain as expected. Before implementing this, I tried a *bunch* of different approaches. I looked into teaching the MCInstLower code to scan up the basic block and find a definition of a register used in a shuffle instruction and then decode that, but this seems incredibly brittle and complex. I talked to Hal a lot about the "right" way to do this: attach the raw shuffle mask to the instruction itself in some form of unencoded operands, and then use that to emit the comments. I still think that's the optimal solution here, but it proved to be beyond what I'm up for here. In particular, it seems likely best done by completing the plumbing of metadata through these layers and attaching the shuffle mask in metadata which could have fully automatic dropping when encoding an actual instruction. llvm-svn: 218377 |
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