third_party/llvm-7.0/llvm/test/Transforms/LoopDeletion/unreachable-loops.ll - SwiftShader - Git at Google

 ; RUN: opt < %s -loop-deletion -verify-dom-info -S | FileCheck %s

 ; Checking that we can delete loops that are never executed.
 ; We do not change the constant conditional branch statement (where the not-taken target
 ; is the loop) to an unconditional one.

 ; delete the infinite loop because it is never executed.
 define void @test1(i64 %n, i64 %m) nounwind {
 ; CHECK-LABEL: test1
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
 ; CHECK-NOT: bb:
 entry:
   br i1 true, label %return, label %bb

 bb:
   %x.0 = phi i64 [ 0, %entry ], [ %t0, %bb ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   %t3 = icmp sgt i64 %x.0, %m
   %t4 = and i1 %t1, %t3
   br i1 true, label %bb, label %return

 return:
   ret void
 }

 ; FIXME: We can delete this infinite loop. Currently we do not,
 ; because the infinite loop has no exit block.
 define void @test2(i64 %n, i64 %m) nounwind {
 ; CHECK-LABEL: test2
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
 ; CHECK-LABEL: bb:
 ; CHECK: br label %bb
 entry:
   br i1 true, label %return, label %bb

 bb:
   %x.0 = phi i64 [ 0, %entry ], [ %t0, %bb ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   %t3 = icmp sgt i64 %x.0, %m
   %t4 = and i1 %t1, %t3
   br label %bb

 return:
   ret void
 }

 ; There are multiple exiting blocks and a single exit block.
 ; Since it is a never executed loop, we do not care about the values
 ; from different exiting paths and we can
 ; delete the loop.
 define i64 @test3(i64 %n, i64 %m, i64 %maybe_zero) nounwind {

 ; CHECK-NOT: bb:
 ; CHECK-NOT: bb2:
 ; CHECK-NOT: bb3:
 ; CHECK-LABEL: return.loopexit:
 ; CHECK-NEXT: %x.lcssa.ph = phi i64 [ undef, %bb.preheader ]
 ; CHECK-NEXT: br label %return
 ; CHECK-LABEL: return:
 ; CHECK-NEXT: %x.lcssa = phi i64 [ 20, %entry ], [ %x.lcssa.ph, %return.loopexit ]
 ; CHECK-NEXT: ret i64 %x.lcssa
 entry:
   br i1 false, label %bb, label %return

 bb:
   %x.0 = phi i64 [ 0, %entry ], [ %t0, %bb3 ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   br i1 %t1, label %bb2, label %return

 bb2:
   %t2 = icmp slt i64 %x.0, %m
   %unused1 = udiv i64 42, %maybe_zero
   br i1 %t2, label %bb3, label %return

 bb3:
   %t3 = icmp slt i64 %x.0, %m
   %unused2 = sdiv i64 42, %maybe_zero
   br i1 %t3, label %bb, label %return

 return:
 ; the only valid value fo x.lcssa is 20.
   %x.lcssa = phi i64 [ 12, %bb ], [ 14, %bb2 ], [ 16, %bb3 ], [20, %entry ]
   ret i64 %x.lcssa
 }

 ; Cannot delete the loop, since it may be executed at runtime.
 define void @test4(i64 %n, i64 %m, i1 %cond) {
 ; CHECK-LABEL: test4
 ; CHECK-LABEL: bb:
 entry:
   br i1 %cond, label %looppred1, label %looppred2

 looppred1:
   br i1 true, label %return, label %bb

 looppred2:
   br i1 false, label %return, label %bb

 bb:
   %x.0 = phi i64 [ 0, %looppred1 ], [ 1, %looppred2 ], [ %t0, %bb ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   %t3 = icmp sgt i64 %x.0, %m
   %t4 = and i1 %t1, %t3
   br i1 true, label %bb, label %return

 return:
   ret void
 }

 ; multiple constant conditional branches with loop not-taken in all cases.
 define void @test5(i64 %n, i64 %m, i1 %cond) nounwind {
 ; CHECK-LABEL: test5
 ; CHECK-LABEL: looppred1:
 ; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
 ; CHECK-LABEL: looppred2:
 ; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
 ; CHECK-NOT: bb:
 entry:
   br i1 %cond, label %looppred1, label %looppred2

 looppred1:
   br i1 true, label %return, label %bb

 looppred2:
   br i1 true, label %return, label %bb

 bb:
   %x.0 = phi i64 [ 0, %looppred1 ], [ 1, %looppred2 ], [ %t0, %bb ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   %t3 = icmp sgt i64 %x.0, %m
   %t4 = and i1 %t1, %t3
   br i1 true, label %bb, label %return

 return:
   ret void
 }

 ; Don't delete this infinite loop because the loop
 ; is executable at runtime.
 define void @test6(i64 %n, i64 %m) nounwind {
 ; CHECK-LABEL: test6
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br i1 true, label %bb.preheader, label %bb.preheader
 ; CHECK: bb:
 entry:
   br i1 true, label %bb, label %bb

 bb:
   %x.0 = phi i64 [ 0, %entry ], [ 0, %entry ], [ %t0, %bb ]
   %t0 = add i64 %x.0, 1
   %t1 = icmp slt i64 %x.0, %n
   %t3 = icmp sgt i64 %x.0, %m
   %t4 = and i1 %t1, %t3
   br i1 true, label %bb, label %return

 return:
   ret void
 }

 declare i64 @foo(i64)
 ; The loop L2 is never executed and is a subloop, with an
 ; exit block that branches back to parent loop.
 ; Here we can delete loop L2, while L1 still exists.
 define i64 @test7(i64 %n) {
 ; CHECK-LABEL: test7
 ; CHECK-LABEL: L1:
 ; CHECK: br i1 true, label %L1Latch, label %L2.preheader
 ; CHECK-LABEL: L2.preheader:
 ; CHECK-NEXT: br label %L1Latch.loopexit
 ; CHECK-LABEL: L1Latch.loopexit:
 ; CHECK: br label %L1Latch
 ; CHECK-LABEL: L1Latch:
 ; CHECK-NEXT: %y = phi i64 [ %y.next, %L1 ], [ %y.L2.lcssa, %L1Latch.loopexit ]
 ; CHECK: br i1 %cond2, label %exit, label %L1
 entry:
   br label %L1

 L1:
   %y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
   br i1 true, label %L1Latch, label %L2

 L2:
   %x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
   %x.next = add i64 %x, 1
   %y.L2 = call i64 @foo(i64 %x.next)
   %cond = icmp slt i64 %x.next, %n
   br i1 %cond, label %L2, label %L1Latch

 L1Latch:
  %y = phi i64 [ %y.next, %L1 ], [ %y.L2, %L2 ]
  %y.add = add i64 %y, %n
  %cond2 = icmp eq i64 %y.add, 42
  br i1 %cond2, label %exit, label %L1

 exit:
  ret i64 %y.add
 }


 ; Show recursive deletion of loops. Since we start with subloops and progress outward
 ; to parent loop, we first delete the loop L2. Now loop L1 becomes a non-loop since it's backedge
 ; from L2's preheader to L1's exit block is never taken. So, L1 gets deleted as well.
 define void @test8(i64 %n) {
 ; CHECK-LABEL: test8
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br label %exit
 ; CHECK-LABEL: exit:
 ; CHECK-NEXT: ret void
 entry:
   br label %L1

 L1:
   br i1 true, label %exit, label %L2

 L2:
   %x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
   %x.next = add i64 %x, 1
   %y.L2 = call i64 @foo(i64 %x.next)
   %cond = icmp slt i64 %x.next, %n
   br i1 %cond, label %L2, label %L1

 exit:
  ret void
 }


 ; Delete a loop (L2) which has subloop (L3).
 ; Here we delete loop L2, but leave L3 as is.
 ; FIXME: Can delete L3 as well, by iteratively going backward through the single
 ; predecessor of L3 until we reach L1's block that guarantees L3 is never
 ; executed.
 define void @test9(i64 %n) {
 ; CHECK-LABEL: test9
 ; CHECK-LABEL: L2.preheader:
 ; CHECK-NEXT: br label %L3.preheader
 ; CHECK-NOT: L2:
 ; CHECK-LABEL: L3.preheader:
 ; CHECK-NEXT: %y.L2.lcssa = phi i64 [ undef, %L2.preheader ]
 ; CHECK-NEXT: br label %L3
 ; CHECK-LABEL: L3:
 ; CHECK: br i1 %cond2, label %L3, label %L1.loopexit
 entry:
   br label %L1

 L1:
   br i1 true, label %exit, label %L2

 L2:
   %x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
   %x.next = add i64 %x, 1
   %y.L2 = call i64 @foo(i64 %x.next)
   %cond = icmp slt i64 %x.next, %n
   br i1 %cond, label %L2, label %L3

 L3:
   %cond2 = icmp slt i64 %y.L2, %n
   br i1 %cond2, label %L3, label %L1

 exit:
  ret void
 }

 ; We cannot delete L3 because of call within it.
 ; Since L3 is not deleted, and entirely contained within L2, L2 is also not
 ; deleted.
 ; FIXME: We can delete unexecutable loops having
 ; subloops contained entirely within them.
 define void @test10(i64 %n) {
 ; CHECK-LABEL: test10
 ; CHECK: L2:
 ; CHECK: L3:
 entry:
   br label %L1

 L1:
   br i1 true, label %exit, label %L2

 L2:
   %x = phi i64 [ 0, %L1 ], [ %x.next, %L3 ]
   %x.next = add i64 %x, 1
   %y.L2 = call i64 @foo(i64 %x.next)
   %cond = icmp slt i64 %x.next, %n
   br i1 %cond, label %L1, label %L3

 L3:
   %y.L3 = phi i64 [ %y.L2, %L2 ], [ %y.L3.next, %L3 ]
   %y.L3.next = add i64 %y.L3, 1
   %dummy = call i64 @foo(i64 %y.L3.next)
   %cond2 = icmp slt i64 %y.L3, %n
   br i1 %cond2, label %L3, label %L2

 exit:
  ret void
 }

 ; same as test10, but L3 does not contain call.
 ; So, in the first iteration, all statements of L3 are made invariant, and L3 is
 ; deleted.
 ; In the next iteration, since L2 is never executed and has no subloops, we delete
 ; L2 as well. Finally, the outermost loop L1 is deleted.
 define void @test11(i64 %n) {
 ; CHECK-LABEL: test11
 ; CHECK-LABEL: entry:
 ; CHECK-NEXT: br label %exit
 ; CHECK-LABEL: exit:
 ; CHECK-NEXT: ret void
 entry:
   br label %L1

 L1:
   br i1 true, label %exit, label %L2

 L2:
   %x = phi i64 [ 0, %L1 ], [ %x.next, %L3 ]
   %x.next = add i64 %x, 1
   %y.L2 = call i64 @foo(i64 %x.next)
   %cond = icmp slt i64 %x.next, %n
   br i1 %cond, label %L1, label %L3

 L3:
   %y.L3 = phi i64 [ %y.L2, %L2 ], [ %y.L3.next, %L3 ]
   %y.L3.next = add i64 %y.L3, 1
   %cond2 = icmp slt i64 %y.L3, %n
   br i1 %cond2, label %L3, label %L2

 exit:
  ret void
 }


 ; 2 edges from a single exiting block to the exit block.
 define i64 @test12(i64 %n){
 ;CHECK-LABEL: @test12
 ; CHECK-NOT: L1:
 ; CHECK-NOT: L1Latch:
 ; CHECK-LABEL: L1.preheader:
 ; CHECK-NEXT:    br label %exit
 ; CHECK-LABEL: exit:
 ; CHECK-NEXT:    %y.phi = phi i64 [ undef, %L1.preheader ]
 ; CHECK-NEXT:    ret i64 %y.phi

 entry:
   br i1 true, label %exit1, label %L1

 exit1:
   ret i64 42

 L1:                                               ; preds = %L1Latch, %entry
   %y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
   br i1 true, label %L1Latch, label %exit

 L1Latch:                                          ; preds = %L1
   %y = phi i64 [ %y.next, %L1 ]
   %y.add = add i64 %y, %n
   %cond2 = icmp eq i64 %y.add, 42
   switch i64 %n, label %L1 [
     i64 10, label %exit
     i64 20, label %exit
   ]

 exit:                                             ; preds = %L1Latch, %L1Latch
   %y.phi = phi i64 [ 10, %L1Latch ], [ 10, %L1Latch ], [ %y.next, %L1]
   ret i64 %y.phi
 }

 ; multiple edges to exit block from the same exiting blocks
 define i64 @test13(i64 %n) {
 ; CHECK-LABEL: @test13
 ; CHECK-NOT: L1:
 ; CHECK-NOT: L1Latch:
 ; CHECK-LABEL: L1.preheader:
 ; CHECK-NEXT:    br label %exit
 ; CHECK-LABEL: exit:
 ; CHECK-NEXT:    %y.phi = phi i64 [ undef, %L1.preheader ]
 ; CHECK-NEXT:    ret i64 %y.phi

 entry:
   br i1 true, label %exit1, label %L1

 exit1:
   ret i64 42

 L1:                                               ; preds = %L1Latch, %entry
   %y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
   br i1 true, label %L1Block, label %exit

 L1Block:                                          ; preds = %L1
   %y = phi i64 [ %y.next, %L1 ]
   %y.add = add i64 %y, %n
   %cond2 = icmp eq i64 %y.add, 42
   switch i64 %n, label %L1Latch [
     i64 10, label %exit
     i64 20, label %exit
   ]

 L1Latch:
   switch i64 %n, label %L1 [
     i64 30, label %exit
     i64 40, label %exit
   ]

 exit:                                             ; preds = %L1Block, %L1, %L1Latch
   %y.phi = phi i64 [ 10, %L1Block ], [ 10, %L1Block ], [ %y.next, %L1 ], [ 30, %L1Latch ], [ 30, %L1Latch ]
   ret i64 %y.phi
 }
	; RUN: opt < %s -loop-deletion -verify-dom-info -S \| FileCheck %s

	; Checking that we can delete loops that are never executed.
	; We do not change the constant conditional branch statement (where the not-taken target
	; is the loop) to an unconditional one.

	; delete the infinite loop because it is never executed.
	define void @test1(i64 %n, i64 %m) nounwind {
	; CHECK-LABEL: test1
	; CHECK-LABEL: entry:
	; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
	; CHECK-NOT: bb:
	entry:
	br i1 true, label %return, label %bb

	bb:
	%x.0 = phi i64 [ 0, %entry ], [ %t0, %bb ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	%t3 = icmp sgt i64 %x.0, %m
	%t4 = and i1 %t1, %t3
	br i1 true, label %bb, label %return

	return:
	ret void
	}

	; FIXME: We can delete this infinite loop. Currently we do not,
	; because the infinite loop has no exit block.
	define void @test2(i64 %n, i64 %m) nounwind {
	; CHECK-LABEL: test2
	; CHECK-LABEL: entry:
	; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
	; CHECK-LABEL: bb:
	; CHECK: br label %bb
	entry:
	br i1 true, label %return, label %bb

	bb:
	%x.0 = phi i64 [ 0, %entry ], [ %t0, %bb ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	%t3 = icmp sgt i64 %x.0, %m
	%t4 = and i1 %t1, %t3
	br label %bb

	return:
	ret void
	}

	; There are multiple exiting blocks and a single exit block.
	; Since it is a never executed loop, we do not care about the values
	; from different exiting paths and we can
	; delete the loop.
	define i64 @test3(i64 %n, i64 %m, i64 %maybe_zero) nounwind {

	; CHECK-NOT: bb:
	; CHECK-NOT: bb2:
	; CHECK-NOT: bb3:
	; CHECK-LABEL: return.loopexit:
	; CHECK-NEXT: %x.lcssa.ph = phi i64 [ undef, %bb.preheader ]
	; CHECK-NEXT: br label %return
	; CHECK-LABEL: return:
	; CHECK-NEXT: %x.lcssa = phi i64 [ 20, %entry ], [ %x.lcssa.ph, %return.loopexit ]
	; CHECK-NEXT: ret i64 %x.lcssa
	entry:
	br i1 false, label %bb, label %return

	bb:
	%x.0 = phi i64 [ 0, %entry ], [ %t0, %bb3 ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	br i1 %t1, label %bb2, label %return

	bb2:
	%t2 = icmp slt i64 %x.0, %m
	%unused1 = udiv i64 42, %maybe_zero
	br i1 %t2, label %bb3, label %return

	bb3:
	%t3 = icmp slt i64 %x.0, %m
	%unused2 = sdiv i64 42, %maybe_zero
	br i1 %t3, label %bb, label %return

	return:
	; the only valid value fo x.lcssa is 20.
	%x.lcssa = phi i64 [ 12, %bb ], [ 14, %bb2 ], [ 16, %bb3 ], [20, %entry ]
	ret i64 %x.lcssa
	}

	; Cannot delete the loop, since it may be executed at runtime.
	define void @test4(i64 %n, i64 %m, i1 %cond) {
	; CHECK-LABEL: test4
	; CHECK-LABEL: bb:
	entry:
	br i1 %cond, label %looppred1, label %looppred2

	looppred1:
	br i1 true, label %return, label %bb

	looppred2:
	br i1 false, label %return, label %bb

	bb:
	%x.0 = phi i64 [ 0, %looppred1 ], [ 1, %looppred2 ], [ %t0, %bb ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	%t3 = icmp sgt i64 %x.0, %m
	%t4 = and i1 %t1, %t3
	br i1 true, label %bb, label %return

	return:
	ret void
	}

	; multiple constant conditional branches with loop not-taken in all cases.
	define void @test5(i64 %n, i64 %m, i1 %cond) nounwind {
	; CHECK-LABEL: test5
	; CHECK-LABEL: looppred1:
	; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
	; CHECK-LABEL: looppred2:
	; CHECK-NEXT: br i1 true, label %return, label %bb.preheader
	; CHECK-NOT: bb:
	entry:
	br i1 %cond, label %looppred1, label %looppred2

	looppred1:
	br i1 true, label %return, label %bb

	looppred2:
	br i1 true, label %return, label %bb

	bb:
	%x.0 = phi i64 [ 0, %looppred1 ], [ 1, %looppred2 ], [ %t0, %bb ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	%t3 = icmp sgt i64 %x.0, %m
	%t4 = and i1 %t1, %t3
	br i1 true, label %bb, label %return

	return:
	ret void
	}

	; Don't delete this infinite loop because the loop
	; is executable at runtime.
	define void @test6(i64 %n, i64 %m) nounwind {
	; CHECK-LABEL: test6
	; CHECK-LABEL: entry:
	; CHECK-NEXT: br i1 true, label %bb.preheader, label %bb.preheader
	; CHECK: bb:
	entry:
	br i1 true, label %bb, label %bb

	bb:
	%x.0 = phi i64 [ 0, %entry ], [ 0, %entry ], [ %t0, %bb ]
	%t0 = add i64 %x.0, 1
	%t1 = icmp slt i64 %x.0, %n
	%t3 = icmp sgt i64 %x.0, %m
	%t4 = and i1 %t1, %t3
	br i1 true, label %bb, label %return

	return:
	ret void
	}

	declare i64 @foo(i64)
	; The loop L2 is never executed and is a subloop, with an
	; exit block that branches back to parent loop.
	; Here we can delete loop L2, while L1 still exists.
	define i64 @test7(i64 %n) {
	; CHECK-LABEL: test7
	; CHECK-LABEL: L1:
	; CHECK: br i1 true, label %L1Latch, label %L2.preheader
	; CHECK-LABEL: L2.preheader:
	; CHECK-NEXT: br label %L1Latch.loopexit
	; CHECK-LABEL: L1Latch.loopexit:
	; CHECK: br label %L1Latch
	; CHECK-LABEL: L1Latch:
	; CHECK-NEXT: %y = phi i64 [ %y.next, %L1 ], [ %y.L2.lcssa, %L1Latch.loopexit ]
	; CHECK: br i1 %cond2, label %exit, label %L1
	entry:
	br label %L1

	L1:
	%y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
	br i1 true, label %L1Latch, label %L2

	L2:
	%x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
	%x.next = add i64 %x, 1
	%y.L2 = call i64 @foo(i64 %x.next)
	%cond = icmp slt i64 %x.next, %n
	br i1 %cond, label %L2, label %L1Latch

	L1Latch:
	%y = phi i64 [ %y.next, %L1 ], [ %y.L2, %L2 ]
	%y.add = add i64 %y, %n
	%cond2 = icmp eq i64 %y.add, 42
	br i1 %cond2, label %exit, label %L1

	exit:
	ret i64 %y.add
	}


	; Show recursive deletion of loops. Since we start with subloops and progress outward
	; to parent loop, we first delete the loop L2. Now loop L1 becomes a non-loop since it's backedge
	; from L2's preheader to L1's exit block is never taken. So, L1 gets deleted as well.
	define void @test8(i64 %n) {
	; CHECK-LABEL: test8
	; CHECK-LABEL: entry:
	; CHECK-NEXT: br label %exit
	; CHECK-LABEL: exit:
	; CHECK-NEXT: ret void
	entry:
	br label %L1

	L1:
	br i1 true, label %exit, label %L2

	L2:
	%x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
	%x.next = add i64 %x, 1
	%y.L2 = call i64 @foo(i64 %x.next)
	%cond = icmp slt i64 %x.next, %n
	br i1 %cond, label %L2, label %L1

	exit:
	ret void
	}


	; Delete a loop (L2) which has subloop (L3).
	; Here we delete loop L2, but leave L3 as is.
	; FIXME: Can delete L3 as well, by iteratively going backward through the single
	; predecessor of L3 until we reach L1's block that guarantees L3 is never
	; executed.
	define void @test9(i64 %n) {
	; CHECK-LABEL: test9
	; CHECK-LABEL: L2.preheader:
	; CHECK-NEXT: br label %L3.preheader
	; CHECK-NOT: L2:
	; CHECK-LABEL: L3.preheader:
	; CHECK-NEXT: %y.L2.lcssa = phi i64 [ undef, %L2.preheader ]
	; CHECK-NEXT: br label %L3
	; CHECK-LABEL: L3:
	; CHECK: br i1 %cond2, label %L3, label %L1.loopexit
	entry:
	br label %L1

	L1:
	br i1 true, label %exit, label %L2

	L2:
	%x = phi i64 [ 0, %L1 ], [ %x.next, %L2 ]
	%x.next = add i64 %x, 1
	%y.L2 = call i64 @foo(i64 %x.next)
	%cond = icmp slt i64 %x.next, %n
	br i1 %cond, label %L2, label %L3

	L3:
	%cond2 = icmp slt i64 %y.L2, %n
	br i1 %cond2, label %L3, label %L1

	exit:
	ret void
	}

	; We cannot delete L3 because of call within it.
	; Since L3 is not deleted, and entirely contained within L2, L2 is also not
	; deleted.
	; FIXME: We can delete unexecutable loops having
	; subloops contained entirely within them.
	define void @test10(i64 %n) {
	; CHECK-LABEL: test10
	; CHECK: L2:
	; CHECK: L3:
	entry:
	br label %L1

	L1:
	br i1 true, label %exit, label %L2

	L2:
	%x = phi i64 [ 0, %L1 ], [ %x.next, %L3 ]
	%x.next = add i64 %x, 1
	%y.L2 = call i64 @foo(i64 %x.next)
	%cond = icmp slt i64 %x.next, %n
	br i1 %cond, label %L1, label %L3

	L3:
	%y.L3 = phi i64 [ %y.L2, %L2 ], [ %y.L3.next, %L3 ]
	%y.L3.next = add i64 %y.L3, 1
	%dummy = call i64 @foo(i64 %y.L3.next)
	%cond2 = icmp slt i64 %y.L3, %n
	br i1 %cond2, label %L3, label %L2

	exit:
	ret void
	}

	; same as test10, but L3 does not contain call.
	; So, in the first iteration, all statements of L3 are made invariant, and L3 is
	; deleted.
	; In the next iteration, since L2 is never executed and has no subloops, we delete
	; L2 as well. Finally, the outermost loop L1 is deleted.
	define void @test11(i64 %n) {
	; CHECK-LABEL: test11
	; CHECK-LABEL: entry:
	; CHECK-NEXT: br label %exit
	; CHECK-LABEL: exit:
	; CHECK-NEXT: ret void
	entry:
	br label %L1

	L1:
	br i1 true, label %exit, label %L2

	L2:
	%x = phi i64 [ 0, %L1 ], [ %x.next, %L3 ]
	%x.next = add i64 %x, 1
	%y.L2 = call i64 @foo(i64 %x.next)
	%cond = icmp slt i64 %x.next, %n
	br i1 %cond, label %L1, label %L3

	L3:
	%y.L3 = phi i64 [ %y.L2, %L2 ], [ %y.L3.next, %L3 ]
	%y.L3.next = add i64 %y.L3, 1
	%cond2 = icmp slt i64 %y.L3, %n
	br i1 %cond2, label %L3, label %L2

	exit:
	ret void
	}


	; 2 edges from a single exiting block to the exit block.
	define i64 @test12(i64 %n){
	;CHECK-LABEL: @test12
	; CHECK-NOT: L1:
	; CHECK-NOT: L1Latch:
	; CHECK-LABEL: L1.preheader:
	; CHECK-NEXT: br label %exit
	; CHECK-LABEL: exit:
	; CHECK-NEXT: %y.phi = phi i64 [ undef, %L1.preheader ]
	; CHECK-NEXT: ret i64 %y.phi

	entry:
	br i1 true, label %exit1, label %L1

	exit1:
	ret i64 42

	L1: ; preds = %L1Latch, %entry
	%y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
	br i1 true, label %L1Latch, label %exit

	L1Latch: ; preds = %L1
	%y = phi i64 [ %y.next, %L1 ]
	%y.add = add i64 %y, %n
	%cond2 = icmp eq i64 %y.add, 42
	switch i64 %n, label %L1 [
	i64 10, label %exit
	i64 20, label %exit
	]

	exit: ; preds = %L1Latch, %L1Latch
	%y.phi = phi i64 [ 10, %L1Latch ], [ 10, %L1Latch ], [ %y.next, %L1]
	ret i64 %y.phi
	}

	; multiple edges to exit block from the same exiting blocks
	define i64 @test13(i64 %n) {
	; CHECK-LABEL: @test13
	; CHECK-NOT: L1:
	; CHECK-NOT: L1Latch:
	; CHECK-LABEL: L1.preheader:
	; CHECK-NEXT: br label %exit
	; CHECK-LABEL: exit:
	; CHECK-NEXT: %y.phi = phi i64 [ undef, %L1.preheader ]
	; CHECK-NEXT: ret i64 %y.phi

	entry:
	br i1 true, label %exit1, label %L1

	exit1:
	ret i64 42

	L1: ; preds = %L1Latch, %entry
	%y.next = phi i64 [ 0, %entry ], [ %y.add, %L1Latch ]
	br i1 true, label %L1Block, label %exit

	L1Block: ; preds = %L1
	%y = phi i64 [ %y.next, %L1 ]
	%y.add = add i64 %y, %n
	%cond2 = icmp eq i64 %y.add, 42
	switch i64 %n, label %L1Latch [
	i64 10, label %exit
	i64 20, label %exit
	]

	L1Latch:
	switch i64 %n, label %L1 [
	i64 30, label %exit
	i64 40, label %exit
	]

	exit: ; preds = %L1Block, %L1, %L1Latch
	%y.phi = phi i64 [ 10, %L1Block ], [ 10, %L1Block ], [ %y.next, %L1 ], [ 30, %L1Latch ], [ 30, %L1Latch ]
	ret i64 %y.phi
	}