[llvm] [DAGCombine] Remove oneuse restrictions for RISCV in folding (shl (add_nsw x, c1)), c2) and folding (shl(sext(add x, c1)), c2) in some scenarios (PR #101294)

[Craig Topper via llvm-commits]

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@@ -18151,8 +18151,46 @@ bool RISCVTargetLowering::isDesirableToCommuteWithShift(
   //   (shl (or x, c1), c2) -> (or (shl x, c2), c1 << c2)
   SDValue N0 = N->getOperand(0);
   EVT Ty = N0.getValueType();
+
+  // LD/ST will optimize constant Offset extraction, so when AddNode is used by
+  // LD/ST, it can still complete the folding optimization operation performed
+  // above.
+  auto isLDST = [&]() {
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topperc wrote:

This function name isn't great. Should it be `isUsedByLdSt`?

https://github.com/llvm/llvm-project/pull/101294