Revert "Revert r275883 and r275891. They seem to cause PR28608."

This reverts commit r276064, and thus reapplies r275891 and r275883 with
a fix for PR28608.

llvm-svn: 276077

1 files changed, 76 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopSimplify/pr28272.ll b/llvm/test/Transforms/LoopSimplify/pr28272.ll
new file mode 100644
index 00000000000..49990f92cab
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplify/pr28272.ll
@@ -0,0 +1,76 @@
+; RUN: opt < %s -lcssa -loop-unroll -S | FileCheck %s
+target triple = "x86_64-unknown-linux-gnu"
+
+; PR28272
+; When LoopSimplify separates nested loops, it might break LCSSA form: values
+; from the original loop might be used in the outer loop. This test invokes
+; loop-unroll, which calls loop-simplify before itself. If LCSSA is broken
+; after loop-simplify, we crash on assertion.
+
+; CHECK-LABEL: @foo
+define void @foo() {
+entry:
+  br label %header
+
+header:
+  br label %loop1
+
+loop1:
+  br i1 true, label %loop1, label %bb43
+
+bb43:
+  %a = phi i32 [ undef, %loop1 ], [ 0, %bb45 ], [ %a, %bb54 ]
+  %b = phi i32 [ 0, %loop1 ], [ 1, %bb54 ], [ %c, %bb45 ]
+  br i1 true, label %bb114, label %header
+
+bb114:
+  %c = add i32 0, 1
+  %d = add i32 0, 1
+  br i1 true, label %bb45, label %bb54
+
+bb45:
+  %x = add i32 %d, 0
+  br label %bb43
+
+bb54:
+  br label %bb43
+}
+
+; CHECK-LABEL: @foo2
+define void @foo2() {
+entry:
+  br label %outer
+
+outer.loopexit:
+  br label %outer
+
+outer:
+  br label %loop1
+
+loop1:
+  br i1 true, label %loop1, label %loop2.preheader
+
+loop2.preheader:
+  %a.ph = phi i32 [ undef, %loop1 ]
+  %b.ph = phi i32 [ 0, %loop1 ]
+  br label %loop2
+
+loop2:
+  %a = phi i32 [ 0, %loop2.if.true ], [ %a, %loop2.if.false ], [ %a.ph, %loop2.preheader ], [0, %bb]
+  %b = phi i32 [ 1, %loop2.if.false ], [ %c, %loop2.if.true ], [ %b.ph, %loop2.preheader ], [%c, %bb]
+  br i1 true, label %loop2.if, label %outer.loopexit
+
+loop2.if:
+  %c = add i32 0, 1
+  switch i32 undef, label %loop2.if.false [i32 0, label %loop2.if.true
+                                       i32 1, label %bb]
+
+loop2.if.true:
+  br i1 undef, label %loop2, label %bb
+
+loop2.if.false:
+  br label %loop2
+
+bb:
+  br label %loop2
+}