[llvm] 5f928a2 - [SLP]Properly define incoming block for user PHI nodes.

[Alexey Bataev via llvm-commits]

Author: Alexey Bataev
Date: 2023-02-21T08:01:24-08:00
New Revision: 5f928a223ef2c14701eab3077a534c1e49269a51

URL: https://github.com/llvm/llvm-project/commit/5f928a223ef2c14701eab3077a534c1e49269a51
DIFF: https://github.com/llvm/llvm-project/commit/5f928a223ef2c14701eab3077a534c1e49269a51.diff

LOG: [SLP]Properly define incoming block for user PHI nodes.

MainOp of the PHI vectorizable entries contains the proper order of
incoming blocks, not the last instruction in the block.

Added: 
    llvm/test/Transforms/SLPVectorizer/phi-not-ordered.ll

Modified: 
    llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
index 3ff40b5c9247e..b0c0c5ff0d2da 100644
--- a/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
+++ b/llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
@@ -8260,10 +8260,16 @@ BoUpSLP::isGatherShuffledEntry(const TreeEntry *TE, ArrayRef<Value *> VL,
   // reused elements too for better cost estimation.
   Instruction &UserInst =
       getLastInstructionInBundle(TE->UserTreeIndices.front().UserTE);
-  auto *PHI = dyn_cast<PHINode>(&UserInst);
-  auto *NodeUI = DT->getNode(
-      PHI ? PHI->getIncomingBlock(TE->UserTreeIndices.front().EdgeIdx)
-          : UserInst.getParent());
+  BasicBlock *ParentBB = nullptr;
+  // Main node of PHI entries keeps the correct order of operands/incoming
+  // blocks.
+  if (auto *PHI =
+          dyn_cast<PHINode>(TE->UserTreeIndices.front().UserTE->getMainOp())) {
+    ParentBB = PHI->getIncomingBlock(TE->UserTreeIndices.front().EdgeIdx);
+  } else {
+    ParentBB = UserInst.getParent();
+  }
+  auto *NodeUI = DT->getNode(ParentBB);
   assert(NodeUI && "Should only process reachable instructions");
   SmallPtrSet<Value *, 4> GatheredScalars(VL.begin(), VL.end());
   auto CheckOrdering = [&](Instruction *LastEI) {

diff  --git a/llvm/test/Transforms/SLPVectorizer/phi-not-ordered.ll b/llvm/test/Transforms/SLPVectorizer/phi-not-ordered.ll
new file mode 100644
index 0000000000000..9ccadf69c26be
--- /dev/null
+++ b/llvm/test/Transforms/SLPVectorizer/phi-not-ordered.ll
@@ -0,0 +1,32 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -passes=slp-vectorizer -S < %s | FileCheck %s
+
+define void @f(i16 %0) {
+; CHECK-LABEL: @f(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    br label [[FOR_COND:%.*]]
+; CHECK:       for.cond:
+; CHECK-NEXT:    [[TMP1:%.*]] = phi i16 [ 0, [[FOR_END5:%.*]] ], [ [[TMP0:%.*]], [[ENTRY:%.*]] ]
+; CHECK-NEXT:    [[B_0:%.*]] = phi i16 [ 0, [[ENTRY]] ], [ [[INC:%.*]], [[FOR_END5]] ]
+; CHECK-NEXT:    [[INC]] = add i16 0, 0
+; CHECK-NEXT:    br label [[FOR_BODY2:%.*]]
+; CHECK:       for.body2:
+; CHECK-NEXT:    br label [[FOR_BODY2]]
+; CHECK:       for.end5:
+; CHECK-NEXT:    br label [[FOR_COND]]
+;
+entry:
+  br label %for.cond
+
+for.cond:
+  %1 = phi i16 [ 0, %for.end5 ], [ %0, %entry ]
+  %b.0 = phi i16 [ 0, %entry ], [ %inc, %for.end5 ]
+  %inc = add i16 0, 0
+  br label %for.body2
+
+for.body2:
+  br label %for.body2
+
+for.end5:
+  br label %for.cond
+}