[llvm] Reland "[NVPTX] Support copysign PTX instruction" (PR #108125)

[Matt Arsenault via llvm-commits]

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@@ -4401,6 +4401,10 @@ class TargetLowering : public TargetLoweringBase {
   /// Return true if the target supports ptrauth operand bundles.
   virtual bool supportPtrAuthBundles() const { return false; }
 
+  /// Return true if the target supports FCOPYSIGN nodes with operands of
+  /// mismatched types.
+  virtual bool supportMismatchCopysign() const { return true; }
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arsenm wrote:

This is mostly yet another instance of SDAG being bad with legality rules that aren't expressive enough. globalisel fixes this by having 2 type parameters for copysign 

https://github.com/llvm/llvm-project/pull/108125