[SLP]Ignore root gather node, when searching for reuses

Root gather/buildvector node should be ignored when SLP vectorizer tries
to find matching gather nodes, vectorized earlier. This node is
definitely the last one in the pipeline and it does not have users. It
may cause the compiler crash

Fixes #113143

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -12466,7 +12466,7 @@ BoUpSLP::isGatherShuffledSingleRegisterEntry(
     // Build a list of tree entries where V is used.
     SmallPtrSet<const TreeEntry *, 4> VToTEs;
     for (const TreeEntry *TEPtr : ValueToGatherNodes.find(V)->second) {
-      if (TEPtr == TE)
+      if (TEPtr == TE || TEPtr->Idx == 0)
         continue;
       assert(any_of(TEPtr->Scalars,
                     [&](Value *V) { return GatheredScalars.contains(V); }) &&

llvm/test/Transforms/SLPVectorizer/X86/root-gather-reused-scalar.ll

@@ -0,0 +1,40 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S --passes=slp-vectorizer -mtriple=x86_64-unknown-linux-gnu < %s | FileCheck %s
+
+define void @test(ptr %a, i32 %0, i32 %1, i1 %cmp1) {
+; CHECK-LABEL: define void @test(
+; CHECK-SAME: ptr [[A:%.*]], i32 [[TMP0:%.*]], i32 [[TMP1:%.*]], i1 [[CMP1:%.*]]) {
+; CHECK-NEXT:  [[ENTRY:.*:]]
+; CHECK-NEXT:    [[TMP2:%.*]] = load i32, ptr [[A]], align 4
+; CHECK-NEXT:    [[TOBOOL10_NOT:%.*]] = icmp eq i32 [[TMP0]], 0
+; CHECK-NEXT:    [[CMP4_3:%.*]] = icmp ne i32 [[TMP1]], 0
+; CHECK-NEXT:    [[TMP3:%.*]] = and i1 [[CMP4_3]], [[TOBOOL10_NOT]]
+; CHECK-NEXT:    [[CMP2_2:%.*]] = xor i1 [[TOBOOL10_NOT]], true
+; CHECK-NEXT:    [[CONV3_2:%.*]] = zext i1 [[CMP2_2]] to i32
+; CHECK-NEXT:    [[CMP4_2:%.*]] = icmp ne i32 [[TMP2]], [[CONV3_2]]
+; CHECK-NEXT:    [[CMP2_1:%.*]] = xor i1 [[CMP1]], true
+; CHECK-NEXT:    [[CONV3_1:%.*]] = zext i1 [[CMP2_1]] to i32
+; CHECK-NEXT:    [[CMP4_1:%.*]] = icmp ne i32 [[TMP2]], [[CONV3_1]]
+; CHECK-NEXT:    [[TMP4:%.*]] = select i1 [[TMP3]], i1 [[CMP4_2]], i1 false
+; CHECK-NEXT:    [[TMP5:%.*]] = select i1 [[TMP4]], i1 [[CMP4_1]], i1 false
+; CHECK-NEXT:    [[AND_3:%.*]] = zext i1 [[TMP5]] to i32
+; CHECK-NEXT:    store i32 [[AND_3]], ptr [[A]], align 4
+; CHECK-NEXT:    ret void
+;
+entry:
+  %2 = load i32, ptr %a, align 4
+  %tobool10.not = icmp eq i32 %0, 0
+  %cmp4.3 = icmp ne i32 %1, 0
+  %3 = and i1 %cmp4.3, %tobool10.not
+  %cmp2.2 = xor i1 %tobool10.not, true
+  %conv3.2 = zext i1 %cmp2.2 to i32
+  %cmp4.2 = icmp ne i32 %2, %conv3.2
+  %cmp2.1 = xor i1 %cmp1, true
+  %conv3.1 = zext i1 %cmp2.1 to i32
+  %cmp4.1 = icmp ne i32 %2, %conv3.1
+  %4 = select i1 %3, i1 %cmp4.2, i1 false
+  %5 = select i1 %4, i1 %cmp4.1, i1 false
+  %and.3 = zext i1 %5 to i32
+  store i32 %and.3, ptr %a, align 4
+  ret void
+}