[PATCH] D132718: [LoongArch] Combine add + shl to alsl.[w/d/wu]

[WÁNG Xuěruì via Phabricator via llvm-commits]

xen0n added a comment.

For the patch title: not all shifted additions can be expressed with `alsl.*` due to the limited imm range, so we could say `Combine eligible add + shl ...` to better convey the meaning.

Also you could add some more tests covering other possible choices of the imm, and one negative test case showing non-powers-of-2 multipliers are not covered. It may or may not be complete (that would probably cause the testcase number to explode), just some coverage would be nice.



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Comment at: llvm/lib/Target/LoongArch/LoongArchInstrInfo.td:737
 
+/// Shift and add
+let Predicates = [IsLA32] in {
----------------
"Shifted addition"?


================
Comment at: llvm/lib/Target/LoongArch/LoongArchInstrInfo.td:745
+          (ALSL_D GPR:$rj, GPR:$rk, uimm2_plus1:$imm2)>;
+def : Pat<(loongarch_bstrpick (add GPR:$rk, (shl GPR:$rj, uimm2_plus1:$imm2)),
+                              (i64 31), (i64 0)),
----------------
This feels a bit weird, could a more generic node be used here instead of the rather concrete `bstrpick` one?


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https://reviews.llvm.org/D132718