forked from OSchip/llvm-project
5264cc772c
This is a fix for: https://llvm.org/bugs/show_bug.cgi?id=26308 With the switch to using the TTI cost model in: http://reviews.llvm.org/rL228826 ...it became possible to hit a zero-cost cycle of instructions (gep -> phi -> gep...), so we need a cap for the recursion in DominatesMergePoint(). A recursion depth parameter was already added for a different reason in: http://reviews.llvm.org/rL255660 ...so we can just set a limit for it. I pulled "10" out of the air and made it an independent parameter that we can play with. It might be higher than it needs to be given the currently low default value of PHINodeFoldingThreshold (2). That's the starting cost value that we enter the recursion with, and most instructions have cost set to TCC_Basic (1), so I don't think we're going to speculate more than 2 instructions with the current parameters. As noted in the review and the TODO comment, we can do better than just limiting recursion depth. Differential Revision: http://reviews.llvm.org/D16637 llvm-svn: 258971 |
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