[PATCH] D111117: [RISCV] Optimize (add (shl x, c0), c1)

[Craig Topper via Phabricator via llvm-commits]

craig.topper added inline comments.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:6474
+      DAG.getNode(ISD::SHL, DL, VT, New0, DAG.getConstant(C0, DL, VT));
+  if (C1 - (C1 >> C0 << C0) == 0)
+    return New1;
----------------
I think you can drop this if, getNode will see the constant is 0 and not produce an ADD node.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:6482
                                  const RISCVSubtarget &Subtarget) {
+  // Transform (add (shl x, c0), c1) ->
+  //           (add (shl (add x, c1>>c0), c0), c1-(c1>>c0<<c0)),
----------------
This comment is already above transformAddImmShlImm, we don't need to repeat it.


================
Comment at: llvm/lib/Target/RISCV/RISCVISelLowering.cpp:6491
+    return V;
   // Transform (add (mul x, c0), c1) ->
   //           (add (mul (add x, c1/c0), c0), c1%c0).
----------------
Just drop this comment. It's already above transformAddImmMulImm.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D111117/new/

https://reviews.llvm.org/D111117