[SLP]Fix PR89614: phis can be reordered, if reuses are not empty.

Need to relax assertion and check ReuseShuffleIndices is not empty, if
the root phi node has reorder indices.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -12229,7 +12229,7 @@ Value *BoUpSLP::vectorizeTree(TreeEntry *E, bool PostponedPHIs) {
   auto *VecTy = FixedVectorType::get(ScalarTy, E->Scalars.size());
   switch (ShuffleOrOp) {
     case Instruction::PHI: {
-      assert((E->ReorderIndices.empty() ||
+      assert((E->ReorderIndices.empty() || !E->ReuseShuffleIndices.empty() ||
               E != VectorizableTree.front().get() ||
               !E->UserTreeIndices.empty()) &&
              "PHI reordering is free.");

llvm/test/Transforms/SLPVectorizer/X86/phi-reordered-reshuffled.ll

@@ -0,0 +1,57 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 4
+; RUN: opt -S --passes=slp-vectorizer -mtriple=x86_64-unknown-linux-gnu -mcpu=znver2 < %s | FileCheck %s
+
+define void @test() {
+; CHECK-LABEL: define void @test(
+; CHECK-SAME: ) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  bb:
+; CHECK-NEXT:    br label [[BB1:%.*]]
+; CHECK:       bb1:
+; CHECK-NEXT:    [[PHI:%.*]] = phi i32 [ 0, [[BB:%.*]] ], [ [[TMP2:%.*]], [[BB1]] ]
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x i32> [ zeroinitializer, [[BB]] ], [ [[TMP3:%.*]], [[BB1]] ]
+; CHECK-NEXT:    [[TMP1:%.*]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <32 x i32> <i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 0, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1, i32 1>
+; CHECK-NEXT:    [[TMP2]] = call i32 @llvm.vector.reduce.mul.v32i32(<32 x i32> [[TMP1]])
+; CHECK-NEXT:    [[TMP3]] = shufflevector <2 x i32> [[TMP0]], <2 x i32> poison, <2 x i32> <i32 1, i32 0>
+; CHECK-NEXT:    br label [[BB1]]
+;
+bb:
+  br label %bb1
+
+bb1:
+  %phi = phi i32 [ 0, %bb ], [ %mul33, %bb1 ]
+  %phi2 = phi i32 [ 0, %bb ], [ %phi3, %bb1 ]
+  %phi3 = phi i32 [ 0, %bb ], [ %phi2, %bb1 ]
+  %mul = mul i32 %phi2, %phi2
+  %mul4 = mul i32 %phi3, %mul
+  %mul5 = mul i32 %phi2, %mul4
+  %mul6 = mul i32 %phi3, %mul5
+  %mul7 = mul i32 %phi2, %mul6
+  %mul8 = mul i32 %phi3, %mul7
+  %mul9 = mul i32 %phi2, %mul8
+  %mul10 = mul i32 %phi3, %mul9
+  %mul11 = mul i32 %phi2, %mul10
+  %mul12 = mul i32 %phi3, %mul11
+  %mul13 = mul i32 %phi2, %mul12
+  %mul14 = mul i32 %phi3, %mul13
+  %mul15 = mul i32 %phi2, %mul14
+  %mul16 = mul i32 %phi3, %mul15
+  %mul17 = mul i32 %phi2, %mul16
+  %mul18 = mul i32 %phi3, %mul17
+  %mul19 = mul i32 %phi2, %mul18
+  %mul20 = mul i32 %phi3, %mul19
+  %mul21 = mul i32 %phi2, %mul20
+  %mul22 = mul i32 %phi3, %mul21
+  %mul23 = mul i32 %phi2, %mul22
+  %mul24 = mul i32 %phi3, %mul23
+  %mul25 = mul i32 %phi2, %mul24
+  %mul26 = mul i32 %phi3, %mul25
+  %mul27 = mul i32 %phi2, %mul26
+  %mul28 = mul i32 %phi3, %mul27
+  %mul29 = mul i32 %phi2, %mul28
+  %mul30 = mul i32 %phi3, %mul29
+  %mul31 = mul i32 %phi2, %mul30
+  %mul32 = mul i32 %phi3, %mul31
+  %mul33 = mul i32 %phi2, %mul32
+  br label %bb1
+}
+