[llvm] [X86] Don't always seperate conditions in `(br (and/or cond0, cond1))` into seperate branches (PR #81689)

[Simon Pilgrim via llvm-commits]

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@@ -596,6 +596,13 @@ class TargetLoweringBase {
   /// avoided.
   bool isJumpExpensive() const { return JumpIsExpensive; }
 
+  virtual bool keepJumpConditionsTogether(const FunctionLoweringInfo &,
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RKSimon wrote:

Add doxygen description

https://github.com/llvm/llvm-project/pull/81689