forked from OSchip/llvm-project
985454e0ac
LiveIntervals due to the two-addr pass generating bogus MI code. The crux of the issue was a loop nesting problem. The intent of the code which attempts to transform instructions before converting them to two-addr form is to defer and reprocess any transformed instructions as the second processing is likely to have more opportunities to coalesce copies, etc. Unfortunately, there was one section of processing that was not deferred -- the INSERT_SUBREG rewriting. Due to quirks of how this rewriting proceeded, not only did it occur early, it removed the bits of information needed for the deferred processing to correctly generate the necessary two address form (specifically inserting a copy), but didn't trigger any immediate assertions and produced what appeared to be already valid two-address from code. Thus, the assertion only fired much later in the pipeline. The fix is to hoist the transformation logic up layer to where it can more firmly defer all further processing, and to teach the normal processing to handle an edge case previously handled as part of the transformation logic. This edge case (already matched tied register operands) needs to *not* defer any steps. As has been brought up repeatedly in the process: wow does this code need refactoring. I *may* squeeze in some time to at least bring sanity to this loop... but wow... =] Thanks to Jakob for helpful hints on the way here, and the review. llvm-svn: 160443 |
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