[llvm] [DAG] Replace getValid*ShiftAmountConstant helpers with getValid*ShiftAmount helpers to support KnownBits analysis (PR #93182)

[Simon Pilgrim via llvm-commits]

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@@ -2598,11 +2595,11 @@ bool TargetLowering::SimplifyDemandedBits(
         break;
 
       if (Src.getNode()->hasOneUse()) {
-        const APInt *ShAmtC =
-            TLO.DAG.getValidShiftAmountConstant(Src, DemandedElts);
-        if (!ShAmtC || ShAmtC->uge(BitWidth))
+        std::optional<uint64_t> ShAmtC =
+            TLO.DAG.getValidShiftAmount(Src, DemandedElts, Depth + 2);
+        if (!ShAmtC || *ShAmtC >= BitWidth)
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RKSimon wrote:

These are 'inner' shifts of shifts. The originals should have used Depth+1 but that was missed. 

https://github.com/llvm/llvm-project/pull/93182