forked from OSchip/llvm-project
b32f3656d2
Currently, an instruction setting the condition code is linked to the instruction using the condition code via a "glue" link in the SelectionDAG. This has a number of drawbacks; in particular, it means the same CC cannot be used by multiple users. It also makes it more difficult to efficiently implement SADDO et. al. This patch changes the back-end to represent CC dependencies as normal values during SelectionDAG matching, along the lines of how this is handled in the X86 back-end already. In addition to the core mechanics of updating all relevant patterns, this requires a number of additional changes: - We now need to be able to spill/restore a CC value into a GPR if necessary. This means providing a copyPhysReg implementation for moves involving CC, and defining getCrossCopyRegClass. - Since we still prefer to avoid such spills, we provide an override for IsProfitableToFold to avoid creating a merged LOAD / ICMP if this would result in multiple users of the CC. - combineCCMask no longer requires a single CC user, and no longer need to be careful about preventing invalid glue/chain cycles. - emitSelect needs to be more careful in marking CC live-in to the basic block it generates. Also, we can now optimize the case of multiple subsequent selects with the same condition just like X86 does. llvm-svn: 331202 |
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| Analysis | ||
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| BinaryFormat | ||
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| CodeGen | ||
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| Demangle | ||
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| IRReader | ||
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| LineEditor | ||
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| Passes | ||
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| WindowsManifest | ||
| XRay | ||
| CMakeLists.txt | ||
| LLVMBuild.txt | ||