[SLP]Check the MainOp matches the requirements for the instructions

Need to include MainOp into the analysis of the instructions in
getSameOpcode to be sure that it is checked for the requirements to
prevent crashes during further analysis.

Author: alexey-bataev

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -963,8 +963,9 @@ static InstructionsState getSameOpcode(ArrayRef<Value *> VL,
       return InstructionsState::invalid();
   }
   bool AnyPoison = InstCnt != VL.size();
-  // Skip MainOp.
-  for (Value *V : iterator_range(It + 1, VL.end())) {
+  // Check MainOp too to be sure that it matches the requirements for the
+  // instructions.
+  for (Value *V : iterator_range(It, VL.end())) {
     auto *I = dyn_cast<Instruction>(V);
     if (!I)
       continue;

llvm/test/Transforms/SLPVectorizer/ARM/main-gep-with-non-matching-reqs.ll

@@ -0,0 +1,22 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S --passes=slp-vectorizer -mtriple=thumb7 -mcpu=swift < %s | FileCheck %s
+
+define i32 @test(ptr  %0) {
+; CHECK-LABEL: define i32 @test(
+; CHECK-SAME: ptr [[TMP0:%.*]]) #[[ATTR0:[0-9]+]] {
+; CHECK-NEXT:  [[CONT2:.*:]]
+; CHECK-NEXT:    [[ARRAYIDX518:%.*]] = getelementptr i16, ptr [[TMP0]], i32 0
+; CHECK-NEXT:    [[CMP524_NOT:%.*]] = icmp eq ptr [[ARRAYIDX518]], null
+; CHECK-NEXT:    [[ARRAYIDX482_2:%.*]] = getelementptr [4 x i16], ptr null, i32 0, i32 0
+; CHECK-NEXT:    [[CMP487_NOT_2:%.*]] = icmp eq ptr [[ARRAYIDX482_2]], null
+; CHECK-NEXT:    ret i32 0
+;
+cont2:
+  %arrayidx518 = getelementptr i16, ptr  %0, i32 0
+  %cmp524.not = icmp eq ptr  %arrayidx518, null
+  %cmp487.not.3 = icmp eq ptr  null, null
+  %arrayidx482.2 = getelementptr [4 x i16], ptr  null, i32 0, i32 0
+  %cmp487.not.2 = icmp eq ptr  %arrayidx482.2, null
+  %cmp487.not.1 = icmp eq ptr  null, null
+  ret i32 0
+}