[llvm] [GlobalISel] Add iterative known-bits evaluation to GISelValueTracking (PR #221755)

[Matt Arsenault via llvm-commits]

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@@ -64,8 +66,9 @@ class LLVM_ABI GISelValueTracking : public GISelChangeObserver {
 
   const DataLayout &getDataLayout() const { return DL; }
 
-  void computeKnownBitsImpl(Register R, KnownBits &Known,
-                            const APInt &DemandedElts, unsigned Depth = 0);
+  virtual void computeKnownBitsImpl(Register R, KnownBits &Known,
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arsenm wrote:

If we're going to do this, we should have one iterative implementation. No retention of the old recursion 

https://github.com/llvm/llvm-project/pull/221755