[SimpleLoopUnswitch] Form dedicated exits after trivial unswitches.

Summary:
Form dedicated exits after trivial unswitches.
Fixes PR38737, PR38283.

Reviewers: chandlerc, fedor.sergeev

Subscribers: sanjoy, jlebar, uabelho, llvm-commits

Differential Revision: https://reviews.llvm.org/D51375

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340871 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimpleLoopUnswitch/formDedicatedAfterTrivial1.ll

@@ -0,0 +1,25 @@
+; RUN: opt < %s -simple-loop-unswitch -disable-output
+
+; PR38283
+; PR38737
+define void @f1() {
+for.cond1thread-pre-split.lr.ph.lr.ph:
+  %tobool4 = icmp eq i16 undef, 0
+  br label %for.cond1thread-pre-split
+
+for.cond1thread-pre-split:                        ; preds = %if.end, %for.cond1thread-pre-split.lr.ph.lr.ph
+  %tobool3 = icmp eq i16 undef, 0
+  br label %for.body2
+
+for.body2:                                        ; preds = %if.end6, %for.cond1thread-pre-split
+  br i1 %tobool3, label %if.end, label %for.end
+
+if.end:                                           ; preds = %for.body2
+  br i1 %tobool4, label %if.end6, label %for.cond1thread-pre-split
+
+if.end6:                                          ; preds = %if.end
+  br i1 undef, label %for.body2, label %for.end
+
+for.end:                                          ; preds = %if.end6, %for.body2
+  ret void
+}

test/Transforms/SimpleLoopUnswitch/formDedicatedAfterTrivial2.ll

@@ -0,0 +1,22 @@
+; RUN: opt < %s -simple-loop-unswitch -disable-output
+
+; PR38283
+; PR38737
+define void @Test(i32) {
+entry:
+  %trunc = trunc i32 %0 to i3
+  br label %outer
+outer:
+  br label %inner
+inner:
+  switch i3 %trunc, label %crit_edge [
+    i3 2, label %break
+    i3 1, label %loopexit
+  ]
+crit_edge:
+  br i1 true, label %loopexit, label %inner
+loopexit:
+  ret void
+break:
+  br label %outer
+}

test/Transforms/SimpleLoopUnswitch/formDedicatedAfterTrivial3.ll

@@ -0,0 +1,37 @@
+; RUN: opt < %s -simple-loop-unswitch -disable-output
+
+; PR38283
+; PR38737
+declare void @func_1()
+
+define void @func_9(i32 signext %arg) {
+bb:
+  br label %bb5
+bb5:                                              ; preds = %bb24, %bb
+  %tmp3.0 = phi i32 [ undef, %bb ], [ %tmp29, %bb24 ]
+  %tmp11 = icmp eq i32 %arg, 0
+  %tmp15 = icmp eq i32 %tmp3.0, 0
+  %spec.select = select i1 %tmp15, i32 0, i32 49
+  %tmp1.2 = select i1 %tmp11, i32 %spec.select, i32 9
+  %trunc = trunc i32 %tmp1.2 to i6
+  br label %bb9
+
+bb9:                                              ; preds = %bb5, %bb19
+  %tmp2.03 = phi i32 [ 0, %bb5 ], [ %tmp21, %bb19 ]
+  switch i6 %trunc, label %bb24 [
+    i6 0, label %bb19
+    i6 -15, label %bb22
+  ]
+
+bb19:                                             ; preds = %bb9
+  %tmp21 = add nuw nsw i32 %tmp2.03, 1
+  %tmp8 = icmp eq i32 %tmp21, 25
+  br i1 %tmp8, label %bb22, label %bb9
+
+bb22:                                             ; preds = %bb19, %bb9
+  unreachable
+
+bb24:                                             ; preds = %bb9
+  %tmp29 = or i32 %tmp3.0, 1
+  br label %bb5
+}