[PATCH] D107711: [DAGCombiner] Add target hook function to decide folding (mul (add x, c1), c2)

[Ben Shi via Phabricator via llvm-commits]

benshi001 added inline comments.


================
Comment at: llvm/test/CodeGen/RISCV/addimm-mulimm.ll:305
+; RV64IM-NEXT:    addi a1, zero, 192
+; RV64IM-NEXT:    mulw a0, a0, a1
 ; RV64IM-NEXT:    ret
----------------
benshi001 wrote:
> This can be further optimized to
> 
> (SLLIW (SH1ADD a0, a0, a0), 6).
> 
> I will make another patch for this optimization.
The best form should be

; RV64IM-NEXT:    addi a0, a0, 1000
; RV64IM-NEXT:    sh1add a0, a0, a0
; RV64IM-NEXT:    slliw a0, a0, 6

It can be done via new rules in RISCVInstrInfoB.td


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  https://reviews.llvm.org/D107711/new/

https://reviews.llvm.org/D107711