Revert "[SLP] Improve gather tree nodes matching when users are PHIs. (#69392)"

This reverts commit c80b503.

This change causes a fatal error in the backend and is filed as issue #69670.

Author: dyung

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -9043,7 +9043,6 @@ BoUpSLP::isGatherShuffledEntry(const TreeEntry *TE, ArrayRef<Value *> VL,
   // blocks.
   if (auto *PHI = dyn_cast<PHINode>(TEUseEI.UserTE->getMainOp())) {
     TEInsertBlock = PHI->getIncomingBlock(TEUseEI.EdgeIdx);
-    TEInsertPt = TEInsertBlock->getTerminator();
   } else {
     TEInsertBlock = TEInsertPt->getParent();
   }
@@ -9107,10 +9106,9 @@ BoUpSLP::isGatherShuffledEntry(const TreeEntry *TE, ArrayRef<Value *> VL,
       const Instruction *InsertPt =
           UserPHI ? UserPHI->getIncomingBlock(UseEI.EdgeIdx)->getTerminator()
                   : &getLastInstructionInBundle(UseEI.UserTE);
-      if (TEInsertPt == InsertPt) {
-        // If 2 gathers are operands of the same entry (regardless of wether
-        // user is PHI or else), compare operands indices, use the earlier one
-        // as the base.
+      if (!UserPHI && TEInsertPt == InsertPt) {
+        // If 2 gathers are operands of the same non-PHI entry,
+        // compare operands indices, use the earlier one as the base.
         if (TEUseEI.UserTE == UseEI.UserTE && TEUseEI.EdgeIdx < UseEI.EdgeIdx)
           continue;
         // If the user instruction is used for some reason in different

llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll

@@ -8,7 +8,7 @@
 ; YAML: Function:        test
 ; YAML: Args:
 ; YAML:   - String:          'Stores SLP vectorized with cost '
-; YAML:   - Cost:            '-6'
+; YAML:   - Cost:            '-3'
 ; YAML:   - String:          ' and with tree size '
 ; YAML:   - TreeSize:        '14'
 ; YAML: ...