[LoopUnroll] Fix the way we update DT after complete unrolling.

Updating dominators for exit-blocks of the unrolled loops is not enough,
as shown in PR27157. The proper way is to update dominators for all
dominance-children of original loop blocks.

llvm-svn: 265605

1 files changed, 53 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopUnroll/pr27157.ll b/llvm/test/Transforms/LoopUnroll/pr27157.ll
new file mode 100644
index 00000000000..917bcf1f944
--- /dev/null
+++ b/llvm/test/Transforms/LoopUnroll/pr27157.ll
@@ -0,0 +1,53 @@
+; RUN: opt -loop-unroll -debug-only=loop-unroll -disable-output < %s
+; REQUIRES: asserts
+; Compile this test with debug flag on to verify domtree right after loop unrolling.
+target datalayout = "E-m:e-i1:8:16-i8:8:16-i64:64-f128:64-v128:64-a:8:16-n32:64"
+
+; PR27157
+define void @foo() {
+entry:
+  br label %loop_header
+loop_header:
+  %iv = phi i64 [ 0, %entry ], [ %iv_next, %loop_latch ]
+  br i1 undef, label %loop_latch, label %loop_exiting_bb1
+loop_exiting_bb1:
+  br i1 false, label %loop_exiting_bb2, label %exit1.loopexit
+loop_exiting_bb2:
+  br i1 false, label %loop_latch, label %bb
+bb:
+  br label %exit1
+loop_latch:
+  %iv_next = add nuw nsw i64 %iv, 1
+  %cmp = icmp ne i64 %iv_next, 2
+  br i1 %cmp, label %loop_header, label %exit2
+exit1.loopexit:
+  br label %exit1
+exit1:
+  ret void
+exit2:
+  ret void
+}
+
+define void @foo2() {
+entry:
+  br label %loop.header
+loop.header:
+  %iv = phi i32 [ 0, %entry ], [ %iv.inc, %latch ]
+  %iv.inc = add i32 %iv, 1
+  br i1 undef, label %diamond, label %latch
+diamond:
+  br i1 undef, label %left, label %right
+left:
+  br i1 undef, label %exit, label %merge
+right:
+  br i1 undef, label %exit, label %merge
+merge:
+  br label %latch
+latch:
+  %end.cond = icmp eq i32 %iv, 1
+  br i1 %end.cond, label %exit1, label %loop.header
+exit:
+  ret void
+exit1:
+  ret void
+}