[SLP]Fix PR107198: add a check for empty complex type

Need to check if the complex type is empty before trying to dig in,
trying to find vectorizable type

Fixes llvm#107198

llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

@@ -7780,6 +7780,8 @@ unsigned BoUpSLP::canMapToVector(Type *T) const {
   Type *EltTy = T;
 
   while (isa<StructType, ArrayType, FixedVectorType>(EltTy)) {
+    if (EltTy->isEmptyTy())
+      return 0;
     if (auto *ST = dyn_cast<StructType>(EltTy)) {
       // Check that struct is homogeneous.
       for (const auto *Ty : ST->elements())

llvm/test/Transforms/SLPVectorizer/empty-struct.ll

@@ -0,0 +1,14 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S --passes=slp-vectorizer < %s | FileCheck %s
+
+define { { {}, {}, {}, {}, {}, {}, {} } } @test({ {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, { {}, {}, {}, {}, {}, {}, {} }, { {} } } %0) {
+; CHECK-LABEL: define { { {}, {}, {}, {}, {}, {}, {} } } @test(
+; CHECK-SAME: { {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, { {}, {}, {}, {}, {}, {}, {} }, { {} } } [[TMP0:%.*]]) {
+; CHECK-NEXT:    [[TMP2:%.*]] = extractvalue { {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, { {}, {}, {}, {}, {}, {}, {} }, { {} } } [[TMP0]], 18
+; CHECK-NEXT:    [[TMP3:%.*]] = insertvalue { { {}, {}, {}, {}, {}, {}, {} } } undef, { {}, {}, {}, {}, {}, {}, {} } [[TMP2]], 0
+; CHECK-NEXT:    ret { { {}, {}, {}, {}, {}, {}, {} } } [[TMP3]]
+;
+  %2 = extractvalue { {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, {}, { {}, {}, {}, {}, {}, {}, {} }, { {} } } %0, 18
+  %3 = insertvalue { { {}, {}, {}, {}, {}, {}, {} } } undef, { {}, {}, {}, {}, {}, {}, {} } %2, 0
+  ret { { {}, {}, {}, {}, {}, {}, {} } } %3
+}