From 734b016b66c7bc1ef93b294c9bf7bbbd2c02a044 Mon Sep 17 00:00:00 2001
From: Douglas Yung <douglas.yung@sony.com>
Date: Fri, 20 Oct 2023 10:59:07 -0700
Subject: [PATCH] Revert "[SLP] Improve gather tree nodes matching when users
 are PHIs. (#69392)"

This reverts commit c80b50349648dcf7fcbf4ae69c62b3d34bee0c70.

This change causes a fatal error in the backend and is filed as issue #69670.
---
 llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp           | 8 +++-----
 .../SLPVectorizer/X86/matching-gather-nodes-phi-users.ll  | 2 +-
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 1142d2112803..f694ab88ccab 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/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
diff --git a/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll b/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll
index e5d7ad138b4d..28e0b06f6967 100644
--- a/llvm/test/Transforms/SLPVectorizer/X86/matching-gather-nodes-phi-users.ll
+++ b/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: ...