forked from OSchip/llvm-project
9f155bc6e5
Summary: DAGCombine will normally turn a `(shl (add x, c1), c2)` into `(add (shl x, c2), c1 << c2)`, where `c1` and `c2` are constants. This can be prevented by a callback in TargetLowering. On RISC-V, materialising the constant `c1 << c2` can be more expensive than materialising `c1`, because materialising the former may take more instructions, and may use a register, where materialising the latter would not. This patch implements the hook in RISCVTargetLowering to prevent this transform, in the cases where: - `c1` fits into the immediate field in an `addi` instruction. - `c1` takes fewer instructions to materialise than `c1 << c2`. In future, DAGCombine could do the check to see whether `c1` fits into an add immediate, which might simplify more targets hooks than just RISC-V. Reviewers: asb, luismarques, efriedma Reviewed By: asb Subscribers: xbolva00, lebedev.ri, craig.topper, lewis-revill, Jim, hiraditya, rbar, johnrusso, simoncook, apazos, sabuasal, niosHD, kito-cheng, shiva0217, jrtc27, zzheng, edward-jones, rogfer01, MartinMosbeck, brucehoult, the_o, rkruppe, PkmX, jocewei, psnobl, benna, llvm-commits Tags: #llvm Differential Revision: https://reviews.llvm.org/D62857 llvm-svn: 363736 |
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| Analysis | ||
| AsmParser | ||
| BinaryFormat | ||
| Bitcode | ||
| CodeGen | ||
| DebugInfo | ||
| Demangle | ||
| ExecutionEngine | ||
| FuzzMutate | ||
| Fuzzer | ||
| IR | ||
| IRReader | ||
| LTO | ||
| LineEditor | ||
| Linker | ||
| MC | ||
| MCA | ||
| Object | ||
| ObjectYAML | ||
| Option | ||
| Passes | ||
| ProfileData | ||
| Remarks | ||
| Support | ||
| TableGen | ||
| Target | ||
| Testing | ||
| TextAPI | ||
| ToolDrivers | ||
| Transforms | ||
| WindowsManifest | ||
| XRay | ||
| CMakeLists.txt | ||
| LLVMBuild.txt | ||