[llvm] [SandboxVec] Add a simple pack reuse pass (PR #141848)

[via llvm-commits]

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@@ -179,13 +197,61 @@ class VecUtils {
   /// \Returns the first integer power of 2 that is <= Num.
   static unsigned getFloorPowerOf2(unsigned Num);
 
+  /// If \p I is the last instruction of a pack pattern, then this function
+  /// returns the instructions in the pack and the operands in the pack, else
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vporpo wrote:

I agree, I documented this in the description of the `PackPattern` struct.

https://github.com/llvm/llvm-project/pull/141848