forked from OSchip/llvm-project
7fe6a5390f
Aggressive anti-dependency breaking is enabled by default for all PPC cores. This provides a general speedup on the P7 and other platforms (among other factors, the instruction group formation for the non-embedded PPC cores is done during post-RA scheduling). In order to do this safely, the incompatibility between uses of the MFOCRF instruction and anti-dependency breaking are resolved by marking MFOCRF with hasExtraSrcRegAllocReq. As noted in the removed FIXME, the problem was that MFOCRF's output is sensitive to the identify of the source register, and always paired with a shift to undo this effect. Because anti-dependency breaking is unaware of this hidden dependency of the shift amount on the source register of the MFOCRF instruction, changing that register must be inhibited. Two test cases were adjusted: The SjLj test was made more insensitive to register choices and scheduling; the saveCR test disabled anti-dependency breaking because part of what it is testing is proper register reuse. llvm-svn: 190587 |
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