[SLP] Precommit test demonstrating catchswitch crash.

In SLPVectorizer, when computing spill costs for a tree, we call
`BasicBlock::getFirstNonPHIOrDbgOrAlloca()` without checking if its
return value is an end iterator. This can occur if the basic block is a
`catchswitch` block. Dereferencing this iterator in an assertions build
with sentinel-tracking causes a crash. This patch commits a test which
demonstrates this issue.

Author: Tyler Lanphear

llvm/test/Transforms/SLPVectorizer/catchswitch2.ll

@@ -0,0 +1,72 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; REQUIRES: asserts
+; RUN: opt -passes=slp-vectorizer -S < %s | FileCheck %s
+
+; This test demonstrates a crash when trying to compute spill costs when
+; vectorizing a tree in a function which contains a `catchswitch` block.
+
+; XFAIL: *
+
+target triple = "x86_64-pc-windows-msvc19.40.33811"
+
+%"class.boost::execution_exception" = type { i32, %"class.boost::unit_test::basic_cstring", %"struct.boost::execution_exception::location" }
+%"class.boost::unit_test::basic_cstring" = type { ptr, ptr }
+%"struct.boost::execution_exception::location" = type { %"class.boost::unit_test::basic_cstring", i64, %"class.boost::unit_test::basic_cstring" }
+
+define void @foo() personality ptr null {
+; CHECK-LABEL: define void @foo() personality ptr null {
+; CHECK-NEXT:  [[ENTRY:.*]]:
+; CHECK-NEXT:    br label %[[FOR_COND109:.*]]
+; CHECK:       [[FOR_COND109]]:
+; CHECK-NEXT:    [[TMP0:%.*]] = phi <2 x ptr> [ zeroinitializer, %[[ENTRY]] ], [ zeroinitializer, %[[IF_END153:.*]] ]
+; CHECK-NEXT:    br label %[[INIT_ATTEMPT_I664:.*]]
+; CHECK:       [[INIT_ATTEMPT_I664]]:
+; CHECK-NEXT:    [[CALL_I666:%.*]] = invoke ptr null(ptr null)
+; CHECK-NEXT:            to label %[[INVOKE_CONT_I668:.*]] unwind label %[[CATCH_DISPATCH:.*]]
+; CHECK:       [[INVOKE_CONT_I668]]:
+; CHECK-NEXT:    ret void
+; CHECK:       [[CATCH_DISPATCH]]:
+; CHECK-NEXT:    [[TMP1:%.*]] = catchswitch within none [label %catch] unwind to caller
+; CHECK:       [[CATCH:.*]]:
+; CHECK-NEXT:    [[TMP2:%.*]] = catchpad within [[TMP1]] [ptr null, i32 0, ptr null]
+; CHECK-NEXT:    br i1 false, label %[[IF_END153]], label %[[INVOKE_CONT149:.*]]
+; CHECK:       [[INVOKE_CONT149]]:
+; CHECK-NEXT:    [[TMP3:%.*]] = load <2 x ptr>, ptr null, align 8
+; CHECK-NEXT:    br label %[[IF_END153]]
+; CHECK:       [[IF_END153]]:
+; CHECK-NEXT:    [[TMP4:%.*]] = phi <2 x ptr> [ [[TMP0]], %[[CATCH]] ], [ [[TMP3]], %[[INVOKE_CONT149]] ]
+; CHECK-NEXT:    catchret from [[TMP2]] to label %[[FOR_COND109]]
+;
+entry:
+  br label %for.cond109
+
+for.cond109:                                      ; preds = %if.end153, %entry
+  %setup_error.sroa.0.1 = phi ptr [ null, %entry ], [ null, %if.end153 ]
+  %setup_error.sroa.6.1 = phi ptr [ null, %entry ], [ null, %if.end153 ]
+  br label %init.attempt.i664
+
+init.attempt.i664:                                ; preds = %for.cond109
+  %call.i666 = invoke ptr null(ptr null)
+  to label %invoke.cont.i668 unwind label %catch.dispatch
+
+invoke.cont.i668:                                 ; preds = %init.attempt.i664
+  ret void
+
+catch.dispatch:                                   ; preds = %init.attempt.i664
+  %0 = catchswitch within none [label %catch] unwind to caller
+
+catch:                                            ; preds = %catch.dispatch
+  %1 = catchpad within %0 [ptr null, i32 0, ptr null]
+  br i1 false, label %if.end153, label %invoke.cont149
+
+invoke.cont149:                                   ; preds = %catch
+  %m_begin2.i.i = getelementptr %"class.boost::execution_exception", ptr null, i64 0, i32 1, i32 0
+  %2 = load ptr, ptr %m_begin2.i.i, align 8
+  %3 = load ptr, ptr null, align 8
+  br label %if.end153
+
+if.end153:                                        ; preds = %invoke.cont149, %catch
+  %setup_error.sroa.0.2 = phi ptr [ %setup_error.sroa.0.1, %catch ], [ %2, %invoke.cont149 ]
+  %setup_error.sroa.6.2 = phi ptr [ %setup_error.sroa.6.1, %catch ], [ %3, %invoke.cont149 ]
+  catchret from %1 to label %for.cond109
+}