[SLP]Check if the user node has instructions, used only outside

Gather nodes with parents, which scalar instructions are used only
outside, are generated before the whole tree vectorization. Need to
teach isGatherShuffledSingleRegisterEntry to check that such nodes are
emitted first and they cannot depend on other nodes, which are emitted
later.

Fixes #141628

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -15317,6 +15317,20 @@ BoUpSLP::isGatherShuffledSingleRegisterEntry(
           UserPHI ? UserPHI->getIncomingBlock(UseEI.EdgeIdx)->getTerminator()
                   : &getLastInstructionInBundle(UseEI.UserTE);
       if (TEInsertPt == InsertPt) {
+        // Check nodes, which might be emitted first.
+        if (TEUseEI.UserTE->State == TreeEntry::Vectorize &&
+            (TEUseEI.UserTE->getOpcode() != Instruction::PHI ||
+             TEUseEI.UserTE->isAltShuffle()) &&
+            all_of(TEUseEI.UserTE->Scalars,
+                   [](Value *V) { return isUsedOutsideBlock(V); })) {
+          if (UseEI.UserTE->State != TreeEntry::Vectorize ||
+              (UseEI.UserTE->getOpcode() == Instruction::PHI &&
+               !UseEI.UserTE->isAltShuffle()) ||
+              any_of(UseEI.UserTE->Scalars,
+                     [](Value *V) { return !isUsedOutsideBlock(V); }))
+            continue;
+        }
+
         // If the schedulable insertion point is used in multiple entries - just
         // exit, no known ordering at this point, available only after real
         // scheduling.