[llvm] [ReachingDefAnalysis] Track function live-in registers. (PR #177012)

[Mikhail Gudim via llvm-commits]

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@@ -152,8 +152,8 @@ class ReachingDefInfo {
 
   /// Default values are 'nothing happened a long time ago'.
   static constexpr int ReachingDefDefaultVal = -(1 << 21);
-  /// Special values for function live-ins.
-  static constexpr int FunctionLiveInMarker = -1;
+  /// Clearance of live-in registers
+  static constexpr int LiveInClearance = 1;
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mgudim wrote:

so the previous approach didn't quite work because I was trying to stick some other negative number in the defs vector.

https://github.com/llvm/llvm-project/pull/177012