xref: /llvm-project-15.0.7/llvm/test/Transforms/LoopPredication/reverse.ll (revision b2915971)

; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; RUN: opt -S -loop-predication -loop-predication-enable-count-down-loop=true < %s 2>&1 | FileCheck %s
; RUN: opt -S -passes='require<scalar-evolution>,loop-mssa(loop-predication)' -loop-predication-enable-count-down-loop=true < %s 2>&1 | FileCheck %s

declare void @llvm.experimental.guard(i1, ...)

define i32 @signed_reverse_loop_n_to_lower_limit(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @signed_reverse_loop_n_to_lower_limit(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = icmp sge i32 [[LOWERLIMIT:%.*]], 1
; CHECK-NEXT:    [[TMP3:%.*]] = and i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP3]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp sgt i32 [[I]], [[LOWERLIMIT]]
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp sgt i32 %i, %lowerlimit
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}

define i32 @unsigned_reverse_loop_n_to_lower_limit(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @unsigned_reverse_loop_n_to_lower_limit(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = icmp uge i32 [[LOWERLIMIT:%.*]], 1
; CHECK-NEXT:    [[TMP3:%.*]] = and i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP3]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ugt i32 [[I]], [[LOWERLIMIT]]
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp ugt i32 %i, %lowerlimit
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}


; if we predicated the loop, the guard will definitely fail and we will
; deoptimize early on.
define i32 @unsigned_reverse_loop_n_to_0(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @unsigned_reverse_loop_n_to_0(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = and i1 [[TMP1]], false
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP2]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ugt i32 [[I]], 0
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp ugt i32 %i, 0
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}

; do not loop predicate when the range has step -1 and latch has step 1.
define i32 @reverse_loop_range_step_increment(i32 %n, i32* %array, i32 %length) {
; CHECK-LABEL: @reverse_loop_range_step_increment(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[IRC:%.*]] = phi i32 [ [[I_INC:%.*]], [[LOOP]] ], [ 1, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_INC]] = add nuw nsw i32 [[IRC]], 1
; CHECK-NEXT:    [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[IRC]], [[LENGTH:%.*]]
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[WITHIN_BOUNDS]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[IRC]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ugt i32 [[I]], 65534
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %irc = phi i32 [ %i.inc, %loop ], [ 1, %loop.preheader ]
  %i.inc = add nuw nsw i32 %irc, 1
  %within.bounds = icmp ult i32 %irc, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %irc to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %i.next = add nsw i32 %i, -1
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp ugt i32 %i, 65534
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}

define i32 @signed_reverse_loop_n_to_lower_limit_equal(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @signed_reverse_loop_n_to_lower_limit_equal(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = icmp sgt i32 [[LOWERLIMIT:%.*]], 1
; CHECK-NEXT:    [[TMP3:%.*]] = and i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP3]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp sge i32 [[I]], [[LOWERLIMIT]]
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp sge i32 %i, %lowerlimit
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}

define i32 @unsigned_reverse_loop_n_to_lower_limit_equal(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @unsigned_reverse_loop_n_to_lower_limit_equal(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = icmp ugt i32 [[LOWERLIMIT:%.*]], 1
; CHECK-NEXT:    [[TMP3:%.*]] = and i1 [[TMP1]], [[TMP2]]
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP3]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp uge i32 [[I]], [[LOWERLIMIT]]
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp uge i32 %i, %lowerlimit
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}


; if we predicated the loop, the guard will definitely fail and we will
; deoptimize early on.
define i32 @unsigned_reverse_loop_n_to_1(i32* %array, i32 %length, i32 %n, i32 %lowerlimit) {
; CHECK-LABEL: @unsigned_reverse_loop_n_to_1(
; CHECK-NEXT:  entry:
; CHECK-NEXT:    [[TMP5:%.*]] = icmp eq i32 [[N:%.*]], 0
; CHECK-NEXT:    br i1 [[TMP5]], label [[EXIT:%.*]], label [[LOOP_PREHEADER:%.*]]
; CHECK:       loop.preheader:
; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N]], -1
; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[TMP0]], [[LENGTH:%.*]]
; CHECK-NEXT:    [[TMP2:%.*]] = and i1 [[TMP1]], false
; CHECK-NEXT:    br label [[LOOP:%.*]]
; CHECK:       loop:
; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[LOOP]] ], [ 0, [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[LOOP]] ], [ [[N]], [[LOOP_PREHEADER]] ]
; CHECK-NEXT:    [[I_NEXT]] = add nsw i32 [[I]], -1
; CHECK-NEXT:    call void (i1, ...) @llvm.experimental.guard(i1 [[TMP2]], i32 9) [ "deopt"() ]
; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I_NEXT]] to i64
; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I_I64]]
; CHECK-NEXT:    [[ARRAY_I:%.*]] = load i32, i32* [[ARRAY_I_PTR]], align 4
; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC]], [[ARRAY_I]]
; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp uge i32 [[I]], 1
; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
; CHECK:       exit.loopexit:
; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[LOOP]] ]
; CHECK-NEXT:    br label [[EXIT]]
; CHECK:       exit:
; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ 0, [[ENTRY:%.*]] ], [ [[LOOP_ACC_NEXT_LCSSA]], [[EXIT_LOOPEXIT]] ]
; CHECK-NEXT:    ret i32 [[RESULT]]
;
entry:
  %tmp5 = icmp eq i32 %n, 0
  br i1 %tmp5, label %exit, label %loop.preheader

loop.preheader:
  br label %loop

loop:
  %loop.acc = phi i32 [ %loop.acc.next, %loop ], [ 0, %loop.preheader ]
  %i = phi i32 [ %i.next, %loop ], [ %n, %loop.preheader ]
  %i.next = add nsw i32 %i, -1
  %within.bounds = icmp ult i32 %i.next, %length
  call void (i1, ...) @llvm.experimental.guard(i1 %within.bounds, i32 9) [ "deopt"() ]
  %i.i64 = zext i32 %i.next to i64
  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i.i64
  %array.i = load i32, i32* %array.i.ptr, align 4
  %loop.acc.next = add i32 %loop.acc, %array.i
  %continue = icmp uge i32 %i, 1
  br i1 %continue, label %loop, label %exit

exit:
  %result = phi i32 [ 0, %entry ], [ %loop.acc.next, %loop ]
  ret i32 %result
}