1 files changed, 790 insertions, 0 deletions
diff --git a/llvm/test/Transforms/IndVarSimplify/loop-predication.ll b/llvm/test/Transforms/IndVarSimplify/loop-predication.ll
new file mode 100644
index 00000000000..c5fe11a3446
--- /dev/null
+++ b/llvm/test/Transforms/IndVarSimplify/loop-predication.ll
@@ -0,0 +1,790 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt < %s -indvars -indvars-predicate-loops=1 -S | FileCheck %s
+
+declare void @prevent_merging()
+
+; Base case
+define i32 @test1(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @test1(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ugt i32 [[N:%.*]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP0]], i32 [[N]], i32 1
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ult i32 [[LENGTH:%.*]], [[TMP1]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP2]], i32 [[LENGTH]], i32 [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[LENGTH]], [[UMIN]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP3]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] 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:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i 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
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+; Has side effect which must be reflected
+define i32 @neg_store(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @neg_store(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[I]], [[LENGTH:%.*]]
+; CHECK-NEXT:    br i1 [[WITHIN_BOUNDS]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] 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:    store i32 0, i32* [[ARRAY_I_PTR]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i 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
+  store i32 0, i32* %array.i.ptr
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+declare void @maythrow()
+
+; May exit through implicit exception edge
+define i32 @neg_implicit_exit(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @neg_implicit_exit(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    call void @maythrow()
+; CHECK-NEXT:    [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[I]], [[LENGTH:%.*]]
+; CHECK-NEXT:    br i1 [[WITHIN_BOUNDS]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] 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:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N:%.*]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  call void @maythrow()
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i 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
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+
+
+; Base case, but in LFTR form (just for sanity checking)
+define i32 @test2(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @test2(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = add i32 [[N:%.*]], -1
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[LENGTH:%.*]], [[TMP0]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP1]], i32 [[LENGTH]], i32 [[TMP0]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ne i32 [[LENGTH]], [[UMIN]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP2]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] 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:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ne i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds = icmp ne i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i 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
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ne i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+; br (and rcheck1, rcheck2)
+define i32 @two_range_checks(i32* %array.1, i32 %length.1, i32* %array.2, i32 %length.2, i32 %n) {
+; CHECK-LABEL: @two_range_checks(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[LENGTH_2:%.*]], [[LENGTH_1:%.*]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP0]], i32 [[LENGTH_2]], i32 [[LENGTH_1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[LENGTH_2]], [[LENGTH_1]]
+; CHECK-NEXT:    [[UMIN1:%.*]] = select i1 [[TMP1]], i32 [[LENGTH_2]], i32 [[LENGTH_1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ugt i32 [[N:%.*]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP2]], i32 [[N]], i32 1
+; CHECK-NEXT:    [[TMP3:%.*]] = add i32 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ult i32 [[UMIN1]], [[TMP3]]
+; CHECK-NEXT:    [[UMIN2:%.*]] = select i1 [[TMP4]], i32 [[UMIN1]], i32 [[TMP3]]
+; CHECK-NEXT:    [[TMP5:%.*]] = icmp ne i32 [[UMIN]], [[UMIN2]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP5]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] to i64
+; CHECK-NEXT:    [[ARRAY_1_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_1:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_1_I:%.*]] = load i32, i32* [[ARRAY_1_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_1:%.*]] = add i32 [[LOOP_ACC]], [[ARRAY_1_I]]
+; CHECK-NEXT:    [[ARRAY_2_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_2:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_2_I:%.*]] = load i32, i32* [[ARRAY_2_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC_1]], [[ARRAY_2_I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds.1 = icmp ult i32 %i, %length.1
+  %within.bounds.2 = icmp ult i32 %i, %length.2
+  %within.bounds = and i1 %within.bounds.1, %within.bounds.2
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i to i64
+  %array.1.i.ptr = getelementptr inbounds i32, i32* %array.1, i64 %i.i64
+  %array.1.i = load i32, i32* %array.1.i.ptr, align 4
+  %loop.acc.1 = add i32 %loop.acc, %array.1.i
+  %array.2.i.ptr = getelementptr inbounds i32, i32* %array.2, i64 %i.i64
+  %array.2.i = load i32, i32* %array.2.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc.1, %array.2.i
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+define i32 @three_range_checks(i32* %array.1, i32 %length.1, i32* %array.2, i32 %length.2, i32* %array.3, i32 %length.3, i32 %n) {
+; CHECK-LABEL: @three_range_checks(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[LENGTH_3:%.*]], [[LENGTH_2:%.*]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP0]], i32 [[LENGTH_3]], i32 [[LENGTH_2]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ult i32 [[UMIN]], [[LENGTH_1:%.*]]
+; CHECK-NEXT:    [[UMIN1:%.*]] = select i1 [[TMP1]], i32 [[UMIN]], i32 [[LENGTH_1]]
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ult i32 [[LENGTH_3]], [[LENGTH_2]]
+; CHECK-NEXT:    [[UMIN2:%.*]] = select i1 [[TMP2]], i32 [[LENGTH_3]], i32 [[LENGTH_2]]
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ult i32 [[UMIN2]], [[LENGTH_1]]
+; CHECK-NEXT:    [[UMIN3:%.*]] = select i1 [[TMP3]], i32 [[UMIN2]], i32 [[LENGTH_1]]
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ugt i32 [[N:%.*]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP4]], i32 [[N]], i32 1
+; CHECK-NEXT:    [[TMP5:%.*]] = add i32 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP6:%.*]] = icmp ult i32 [[UMIN3]], [[TMP5]]
+; CHECK-NEXT:    [[UMIN4:%.*]] = select i1 [[TMP6]], i32 [[UMIN3]], i32 [[TMP5]]
+; CHECK-NEXT:    [[TMP7:%.*]] = icmp ne i32 [[UMIN1]], [[UMIN4]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP7]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] to i64
+; CHECK-NEXT:    [[ARRAY_1_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_1:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_1_I:%.*]] = load i32, i32* [[ARRAY_1_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_1:%.*]] = add i32 [[LOOP_ACC]], [[ARRAY_1_I]]
+; CHECK-NEXT:    [[ARRAY_2_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_2:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_2_I:%.*]] = load i32, i32* [[ARRAY_2_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_2:%.*]] = add i32 [[LOOP_ACC_1]], [[ARRAY_2_I]]
+; CHECK-NEXT:    [[ARRAY_3_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_3:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_3_I:%.*]] = load i32, i32* [[ARRAY_3_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC_2]], [[ARRAY_3_I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds.1 = icmp ult i32 %i, %length.1
+  %within.bounds.2 = icmp ult i32 %i, %length.2
+  %within.bounds.3 = icmp ult i32 %i, %length.3
+  %within.bounds.1.and.2 = and i1 %within.bounds.1, %within.bounds.2
+  %within.bounds = and i1 %within.bounds.1.and.2, %within.bounds.3
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i to i64
+  %array.1.i.ptr = getelementptr inbounds i32, i32* %array.1, i64 %i.i64
+  %array.1.i = load i32, i32* %array.1.i.ptr, align 4
+  %loop.acc.1 = add i32 %loop.acc, %array.1.i
+  %array.2.i.ptr = getelementptr inbounds i32, i32* %array.2, i64 %i.i64
+  %array.2.i = load i32, i32* %array.2.i.ptr, align 4
+  %loop.acc.2 = add i32 %loop.acc.1, %array.2.i
+  %array.3.i.ptr = getelementptr inbounds i32, i32* %array.3, i64 %i.i64
+  %array.3.i = load i32, i32* %array.3.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc.2, %array.3.i
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded, %entry
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+; Analogous to the above, but with two distinct branches (on different conditions)
+define i32 @distinct_checks(i32* %array.1, i32 %length.1, i32* %array.2, i32 %length.2, i32* %array.3, i32 %length.3, i32 %n) {
+; CHECK-LABEL: @distinct_checks(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ult i32 [[LENGTH_2:%.*]], [[LENGTH_1:%.*]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP0]], i32 [[LENGTH_2]], i32 [[LENGTH_1]]
+; CHECK-NEXT:    [[TMP1:%.*]] = icmp ugt i32 [[N:%.*]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP1]], i32 [[N]], i32 1
+; CHECK-NEXT:    [[TMP2:%.*]] = add i32 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ult i32 [[UMIN]], [[TMP2]]
+; CHECK-NEXT:    [[UMIN1:%.*]] = select i1 [[TMP3]], i32 [[UMIN]], i32 [[TMP2]]
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ne i32 [[LENGTH_1]], [[UMIN1]]
+; CHECK-NEXT:    [[TMP5:%.*]] = icmp ne i32 [[LENGTH_2]], [[UMIN1]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED1:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED1]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP4]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] to i64
+; CHECK-NEXT:    [[ARRAY_1_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_1:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_1_I:%.*]] = load i32, i32* [[ARRAY_1_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_1:%.*]] = add i32 [[LOOP_ACC]], [[ARRAY_1_I]]
+; CHECK-NEXT:    br i1 [[TMP5]], label [[GUARDED1]], label [[DEOPT2:%.*]], !prof !0
+; CHECK:       deopt2:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded1:
+; CHECK-NEXT:    [[ARRAY_3_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_3:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_3_I:%.*]] = load i32, i32* [[ARRAY_3_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC_1]], [[ARRAY_3_I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED1]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded4, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded1 ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded1 ], [ 0, %loop.preheader ]
+  %within.bounds.1 = icmp ult i32 %i, %length.1
+  br i1 %within.bounds.1, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i to i64
+  %array.1.i.ptr = getelementptr inbounds i32, i32* %array.1, i64 %i.i64
+  %array.1.i = load i32, i32* %array.1.i.ptr, align 4
+  %loop.acc.1 = add i32 %loop.acc, %array.1.i
+  %within.bounds.2 = icmp ult i32 %i, %length.2
+  br i1 %within.bounds.2, label %guarded1, label %deopt2, !prof !0
+
+deopt2:                                           ; preds = %guarded
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded1:                                         ; preds = %guarded1
+  %array.3.i.ptr = getelementptr inbounds i32, i32* %array.3, i64 %i.i64
+  %array.3.i = load i32, i32* %array.3.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc.1, %array.3.i
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ %loop.acc.next, %guarded1 ]
+  ret i32 %result
+}
+
+define i32 @duplicate_checks(i32* %array.1, i32* %array.2, i32* %array.3, i32 %length, i32 %n) {
+; CHECK-LABEL: @duplicate_checks(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ugt i32 [[N:%.*]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP0]], i32 [[N]], i32 1
+; CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP2:%.*]] = icmp ult i32 [[LENGTH:%.*]], [[TMP1]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP2]], i32 [[LENGTH]], i32 [[TMP1]]
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ne i32 [[LENGTH]], [[UMIN]]
+; CHECK-NEXT:    [[TMP4:%.*]] = icmp ne i32 [[LENGTH]], [[UMIN]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED1:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED1]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP3]], label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] to i64
+; CHECK-NEXT:    [[ARRAY_1_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_1:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_1_I:%.*]] = load i32, i32* [[ARRAY_1_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_1:%.*]] = add i32 [[LOOP_ACC]], [[ARRAY_1_I]]
+; CHECK-NEXT:    br i1 [[TMP4]], label [[GUARDED1]], label [[DEOPT2:%.*]], !prof !0
+; CHECK:       deopt2:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded1:
+; CHECK-NEXT:    [[ARRAY_3_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY_3:%.*]], i64 [[I_I64]]
+; CHECK-NEXT:    [[ARRAY_3_I:%.*]] = load i32, i32* [[ARRAY_3_I_PTR]], align 4
+; CHECK-NEXT:    [[LOOP_ACC_NEXT]] = add i32 [[LOOP_ACC_1]], [[ARRAY_3_I]]
+; CHECK-NEXT:    [[I_NEXT]] = add nuw i32 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i32 [[I_NEXT]], [[N]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED1]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:                                   ; preds = %entry
+  br label %loop
+
+loop:                                             ; preds = %guarded4, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded1 ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded1 ], [ 0, %loop.preheader ]
+  %within.bounds.1 = icmp ult i32 %i, %length
+  br i1 %within.bounds.1, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i to i64
+  %array.1.i.ptr = getelementptr inbounds i32, i32* %array.1, i64 %i.i64
+  %array.1.i = load i32, i32* %array.1.i.ptr, align 4
+  %loop.acc.1 = add i32 %loop.acc, %array.1.i
+  %within.bounds.2 = icmp ult i32 %i, %length
+  br i1 %within.bounds.2, label %guarded1, label %deopt2, !prof !0
+
+deopt2:                                           ; preds = %guarded
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded1:                                         ; preds = %guarded1
+  %array.3.i.ptr = getelementptr inbounds i32, i32* %array.3, i64 %i.i64
+  %array.3.i = load i32, i32* %array.3.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc.1, %array.3.i
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp ult i32 %i.next, %n
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ %loop.acc.next, %guarded1 ]
+  ret i32 %result
+}
+
+
+define i32 @provably_taken(i32* %array, i32* %length.ptr) {
+; CHECK-LABEL: @provably_taken(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 false, label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[I_I64:%.*]] = zext i32 [[I]] 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:    [[I_NEXT]] = add nuw nsw i32 [[I]], 1
+; CHECK-NEXT:    br i1 true, label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:
+  %length = load i32, i32* %length.ptr, !range !2
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i32 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.i64 = zext i32 %i 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
+  %i.next = add nuw i32 %i, 1
+  %continue = icmp slt i32 %i.next, 200
+  br i1 %continue, label %loop, label %exit
+
+exit:                                             ; preds = %guarded
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+; Non-latch exits can still be predicated
+define i32 @unconditional_latch(i32* %a, i32 %length) {
+; CHECK-LABEL: @unconditional_latch(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    br i1 false, label [[GUARDED:%.*]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    br label [[LOOP]]
+;
+loop.preheader:
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %i = phi i32 [ %i.next, %guarded ], [ 400, %loop.preheader ]
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  %i.next = add i32 %i, 1
+  br label %loop
+}
+
+; Side effect in loop must run proper number of times
+define i32 @unconditional_latch_with_side_effect(i32* %a, i32 %length) {
+; CHECK-LABEL: @unconditional_latch_with_side_effect(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[I:%.*]] = phi i32 [ [[I_NEXT:%.*]], [[GUARDED:%.*]] ], [ 400, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[I]], [[LENGTH:%.*]]
+; CHECK-NEXT:    br i1 [[WITHIN_BOUNDS]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    store volatile i32 0, i32* [[A:%.*]]
+; CHECK-NEXT:    [[I_NEXT]] = add i32 [[I]], 1
+; CHECK-NEXT:    br label [[LOOP]]
+;
+loop.preheader:
+  br label %loop
+
+loop:                                             ; preds = %guarded, %loop.preheader
+  %i = phi i32 [ %i.next, %guarded ], [ 400, %loop.preheader ]
+  %within.bounds = icmp ult i32 %i, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:                                            ; preds = %loop
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:                                          ; preds = %loop
+  store volatile i32 0, i32* %a
+  %i.next = add i32 %i, 1
+  br label %loop
+}
+
+; Demonstrate that this approach works with IVs of different steps, and types
+; This version uses a manually lftred exit condition to work around an issue described
+; in detail on next test.
+define i32 @different_ivs(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @different_ivs(
+; CHECK-NEXT:  loop.preheader:
+; CHECK-NEXT:    [[N64:%.*]] = zext i32 [[N:%.*]] to i64
+; CHECK-NEXT:    [[TMP0:%.*]] = icmp ugt i64 [[N64]], 1
+; CHECK-NEXT:    [[UMAX:%.*]] = select i1 [[TMP0]], i64 [[N64]], i64 1
+; CHECK-NEXT:    [[TMP1:%.*]] = add nsw i64 [[UMAX]], -1
+; CHECK-NEXT:    [[TMP2:%.*]] = zext i32 [[LENGTH:%.*]] to i64
+; CHECK-NEXT:    [[TMP3:%.*]] = icmp ult i64 [[TMP1]], [[TMP2]]
+; CHECK-NEXT:    [[UMIN:%.*]] = select i1 [[TMP3]], i64 [[TMP1]], i64 [[TMP2]]
+; CHECK-NEXT:    [[TMP4:%.*]] = zext i32 [[LENGTH]] to i64
+; CHECK-NEXT:    [[TMP5:%.*]] = icmp ne i64 [[TMP4]], [[UMIN]]
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER:%.*]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    br i1 [[TMP5]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I]]
+; 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:    [[I_NEXT]] = add nuw nsw i64 [[I]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i64 [[I_NEXT]], [[N64]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT:%.*]]
+; CHECK:       exit:
+; CHECK-NEXT:    [[RESULT:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; CHECK-NEXT:    ret i32 [[RESULT]]
+;
+loop.preheader:
+  %j.start = sub nuw nsw i32 %length, 1
+  %n64 = zext i32 %n to i64
+  br label %loop
+
+loop:
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i64 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %j = phi i32 [ %j.next, %guarded ], [ %j.start, %loop.preheader ]
+  %within.bounds = icmp ne i32 %j, -1
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:
+  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i
+  %array.i = load i32, i32* %array.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc, %array.i
+  %i.next = add nuw i64 %i, 1
+  %j.next = sub nuw i32 %j, 1
+  %continue = icmp ult i64 %i.next, %n64
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ %loop.acc.next, %guarded ]
+  ret i32 %result
+}
+
+; TODO: We're failing to compute an exit count for the bounds check.
+; From some quick analysis, it looks like we don't handle -1 step
+; in howManyLessThans.  Should be a simple fix.
+define i32 @different_ivs2(i32* %array, i32 %length, i32 %n) {
+; CHECK-LABEL: @different_ivs2(
+; CHECK-NEXT:  entry:
+; CHECK-NEXT:    [[POS_LENGTH:%.*]] = icmp sgt i32 [[LENGTH:%.*]], 0
+; CHECK-NEXT:    br i1 [[POS_LENGTH]], label [[LOOP_PREHEADER:%.*]], label [[EXIT:%.*]]
+; CHECK:       loop.preheader:
+; CHECK-NEXT:    [[J_START:%.*]] = sub nuw nsw i32 [[LENGTH]], 1
+; CHECK-NEXT:    [[N64:%.*]] = zext i32 [[N:%.*]] to i64
+; CHECK-NEXT:    br label [[LOOP:%.*]]
+; CHECK:       loop:
+; CHECK-NEXT:    [[LOOP_ACC:%.*]] = phi i32 [ [[LOOP_ACC_NEXT:%.*]], [[GUARDED:%.*]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    [[I:%.*]] = phi i64 [ [[I_NEXT:%.*]], [[GUARDED]] ], [ 0, [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    [[J:%.*]] = phi i32 [ [[J_NEXT:%.*]], [[GUARDED]] ], [ [[J_START]], [[LOOP_PREHEADER]] ]
+; CHECK-NEXT:    [[WITHIN_BOUNDS:%.*]] = icmp ult i32 [[J]], [[LENGTH]]
+; CHECK-NEXT:    br i1 [[WITHIN_BOUNDS]], label [[GUARDED]], label [[DEOPT:%.*]], !prof !0
+; CHECK:       deopt:
+; CHECK-NEXT:    call void @prevent_merging()
+; CHECK-NEXT:    ret i32 -1
+; CHECK:       guarded:
+; CHECK-NEXT:    [[ARRAY_I_PTR:%.*]] = getelementptr inbounds i32, i32* [[ARRAY:%.*]], i64 [[I]]
+; 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:    [[I_NEXT]] = add nuw nsw i64 [[I]], 1
+; CHECK-NEXT:    [[J_NEXT]] = sub nuw i32 [[J]], 1
+; CHECK-NEXT:    [[CONTINUE:%.*]] = icmp ult i64 [[I_NEXT]], [[N64]]
+; CHECK-NEXT:    br i1 [[CONTINUE]], label [[LOOP]], label [[EXIT_LOOPEXIT:%.*]]
+; CHECK:       exit.loopexit:
+; CHECK-NEXT:    [[LOOP_ACC_NEXT_LCSSA:%.*]] = phi i32 [ [[LOOP_ACC_NEXT]], [[GUARDED]] ]
+; 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:
+  %pos_length = icmp sgt i32 %length, 0
+  br i1 %pos_length, label %loop.preheader, label %exit
+
+loop.preheader:
+  %j.start = sub nuw nsw i32 %length, 1
+  %n64 = zext i32 %n to i64
+  br label %loop
+
+loop:
+  %loop.acc = phi i32 [ %loop.acc.next, %guarded ], [ 0, %loop.preheader ]
+  %i = phi i64 [ %i.next, %guarded ], [ 0, %loop.preheader ]
+  %j = phi i32 [ %j.next, %guarded ], [ %j.start, %loop.preheader ]
+  %within.bounds = icmp ult i32 %j, %length
+  br i1 %within.bounds, label %guarded, label %deopt, !prof !0
+
+deopt:
+  call void @prevent_merging()
+  ret i32 -1
+
+guarded:
+  %array.i.ptr = getelementptr inbounds i32, i32* %array, i64 %i
+  %array.i = load i32, i32* %array.i.ptr, align 4
+  %loop.acc.next = add i32 %loop.acc, %array.i
+  %i.next = add nuw i64 %i, 1
+  %j.next = sub nuw i32 %j, 1
+  %continue = icmp ult i64 %i.next, %n64
+  br i1 %continue, label %loop, label %exit
+
+exit:
+  %result = phi i32 [ %loop.acc.next, %guarded ], [0, %entry]
+  ret i32 %result
+}
+
+
+
+declare i32 @llvm.experimental.deoptimize.i32(...)
+
+!0 = !{!"branch_weights", i32 1048576, i32 1}
+!1 = !{i32 1, i32 -2147483648}
+!2 = !{i32 0, i32 50}