[llvm] [InstCombine] Optimistically allow multiple shufflevector uses in foldOpPhi (PR #114278)

[Matthias Braun via llvm-commits]

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@@ -1773,17 +1773,33 @@ Instruction *InstCombinerImpl::foldOpIntoPhi(Instruction &I, PHINode *PN) {
   if (NumPHIValues == 0)
     return nullptr;
 
-  // We normally only transform phis with a single use.  However, if a PHI has
-  // multiple uses and they are all the same operation, we can fold *all* of the
-  // uses into the PHI.
+  // We normally only transform phis with a single use.
+  bool AllUsesIdentical = false;
+  bool MultipleUses = false;
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MatzeB wrote:

In principle we can add more exceptions in the future to allow multiple uses in more situations, so I used the more generic name. Anyway will rename to `MultipleShuffleVectorUses` then as we can always rename in the future when someone actually allows more cases...

https://github.com/llvm/llvm-project/pull/114278