[PATCH] D134706: [AArch64] Lower multiplication by a constant int to shl+sub+shl

[Eli Friedman via Phabricator via llvm-commits]

efriedma added inline comments.


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Comment at: llvm/lib/Target/AArch64/AArch64ISelLowering.cpp:14849
+      AddSubOpc = ISD::SUB;
+      Sub2Shift = true;
     } else
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The use of all these booleans makes the actual code generation difficult to understand.

Maybe we can simplify with a few lambdas?  Name them Shl, Add, Sub, Negate.  Then for each case, write out the operations explicitly.  For example, in this case, instead of setting AddSubOpc  and Sub2Shift, you can write `return Sub(Shl(N0, ShiftAmt), Shl(N0, TrailingZeroes))`.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D134706/new/

https://reviews.llvm.org/D134706