[llvm] [DAG] Lower frem of power-2 using div/trunc/mul+sub (PR #91148)

[Matt Arsenault via llvm-commits]

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@@ -2111,6 +2115,10 @@ class SelectionDAG {
   /// Test whether the given SDValue is known to contain non-zero value(s).
   bool isKnownNeverZero(SDValue Op, unsigned Depth = 0) const;
 
+  /// Test whether the given float value is known to not be negative. 0.0 is
+  /// considered non-negative, -0.0 is considered negative.
+  bool isKnownNonNegativeFP(SDValue Op) const;
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arsenm wrote:

Someday we'll have to reinvent computeKnownFPClass in the DAG... (maybe we could do this in CGP to avoid that) 

https://github.com/llvm/llvm-project/pull/91148