[PATCH] D100769: [RISCV] Optimize addition with immediate

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


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Comment at: llvm/lib/Target/RISCV/RISCVInstrInfo.td:1298
+let Predicates = [IsRV64] in
+def : Pat<(sext_inreg (add GPR:$rs1, (AddiPair GPR:$rs2)), i32),
+          (ADDIW (ADDIW GPR:$rs1, (AddiPairImmB GPR:$rs2)),
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craig.topper wrote:
> Do we need to make sure sext_inreg is the only user of the add? Otherwise we’ll emit two ADDIWs and two ADDIs.
I think if we emitted ADDI followed by ADDIW for sign_ext case, the first ADDI would CSE with the first ADDI from a non-sext case if there were multiple uses. Then we wouldn't need to check for multiple uses.


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  https://reviews.llvm.org/D100769/new/

https://reviews.llvm.org/D100769