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

[Jay Foad via llvm-commits]

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@@ -2159,36 +2159,38 @@ class SelectionDAG {
   /// splatted value it will return SDValue().
   SDValue getSplatValue(SDValue V, bool LegalTypes = false);
 
-  /// If a SHL/SRA/SRL node \p V has a constant or splat constant shift amount
+  /// If a SHL/SRA/SRL node \p V has an uniform shift amount
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jayfoad wrote:

"a uniform" here and below.

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