llvm/test/Transforms/SimpleLoopUnswitch/update-scev-2.ll

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 2
; RUN: opt < %s -passes='print<scalar-evolution>,simple-loop-unswitch<no-nontrivial>,print<scalar-evolution>' -disable-output 2>&1 | FileCheck -check-prefix CHECK-SCEV %s
; RUN: opt < %s -passes='function(loop-deletion,simple-loop-unswitch<no-nontrivial>),verify<scalar-evolution>' -S | FileCheck -check-prefix CHECK-IR %s

; These tests used to hit an assertion failure in llvm::ScalarEvolution::BackedgeTakenInfo::getExact:
;    "We should only have known counts for exiting blocks that dominate latch!"' failed.
;
; Verify that we no longer hit that assert, while we expect to have forgotten SCEV for the outer loop.
; Also added checks to show and verify the IR transformation.


; Before the unswitch:
;
; CHECK-SCEV: Classifying expressions for: @f4
; CHECK-SCEV-NEXT:   %j.0 = phi i16 [ 0, %entry ], [ %0, %sw.bb2 ]
; CHECK-SCEV-NEXT:   -->  {0,+,1}<nuw><nsw><%lbl1> U: [0,3) S: [0,3)               Exits: 2                LoopDispositions: { %lbl1: Computable, %lbl2: Invariant }
; CHECK-SCEV-NEXT:   %0 = add i16 %j.0, 1
; CHECK-SCEV-NEXT:   -->  {1,+,1}<nuw><nsw><%lbl1> U: [1,4) S: [1,4)               Exits: 3                LoopDispositions: { %lbl1: Computable, %lbl2: Invariant }
; CHECK-SCEV-DAG: Loop %lbl2: Unpredictable backedge-taken count.
; CHECK-SCEV-DAG: Loop %lbl1: backedge-taken count is i16 2
;
; After the unswitch:
;
; CHECK-SCEV: Classifying expressions for: @f4
; CHECK-SCEV-NEXT:  %j.0 = phi i16 [ 0, %entry ], [ %0, %sw.bb2 ]
; CHECK-SCEV-NEXT:  -->  {0,+,1}<nuw><nsw><%lbl1> U: [0,-32768) S: [0,-32768)             Exits: <<Unknown>>              LoopDispositions: { %lbl1: Computable }
; CHECK-SCEV-NEXT:  %0 = add i16 %j.0, 1
; CHECK-SCEV-NEXT:  -->  {1,+,1}<nuw><nsw><%lbl1> U: [1,-32768) S: [1,-32768)             Exits: <<Unknown>>              LoopDispositions: { %lbl1: Computable }
; CHECK-SCEV-DAG: Loop %lbl1: Unpredictable backedge-taken count.
; CHECK-SCEV-DAG: Loop %lbl2: <multiple exits> Unpredictable backedge-taken count.


define i16 @f4() {
; CHECK-IR-LABEL: define i16 @f4() {
; CHECK-IR-NEXT:  entry:
; CHECK-IR-NEXT:    br label [[LBL1:%.*]]
; CHECK-IR:       lbl1:
; CHECK-IR-NEXT:    [[J_0:%.*]] = phi i16 [ 0, [[ENTRY:%.*]] ], [ [[TMP0:%.*]], [[SW_BB2:%.*]] ]
; CHECK-IR-NEXT:    switch i16 [[J_0]], label [[LBL1_SPLIT:%.*]] [
; CHECK-IR-NEXT:    i16 0, label [[SW_BB2]]
; CHECK-IR-NEXT:    i16 1, label [[SW_BB2]]
; CHECK-IR-NEXT:    i16 2, label [[LBL3:%.*]]
; CHECK-IR-NEXT:    ]
; CHECK-IR:       lbl1.split:
; CHECK-IR-NEXT:    br label [[LBL2:%.*]]
; CHECK-IR:       lbl2:
; CHECK-IR-NEXT:    br label [[LBL2]]
; CHECK-IR:       sw.bb2:
; CHECK-IR-NEXT:    [[TMP0]] = add i16 [[J_0]], 1
; CHECK-IR-NEXT:    br label [[LBL1]]
; CHECK-IR:       lbl3:
; CHECK-IR-NEXT:    ret i16 0
;
entry:
  br label %lbl1

lbl1:                                             ; preds = %sw.bb2, %entry
  %j.0 = phi i16 [ 0, %entry ], [ %0, %sw.bb2 ]
  br label %lbl2

lbl2:                                             ; preds = %lbl2, %lbl1
  switch i16 %j.0, label %lbl2 [
  i16 0, label %sw.bb2
  i16 1, label %sw.bb2
  i16 2, label %lbl3
  ]

sw.bb2:                                           ; preds = %lbl2, %lbl2
  %0 = add i16 %j.0, 1
  br label %lbl1

lbl3:                                             ; preds = %lbl2
  ret i16 0
}