[LoopSimplify] Preserve LCSSA when removing edges from unreachable blocks.

This fixes PR30454.

llvm-svn: 287379

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/Transforms/LoopSimplify/pr30454.ll b/llvm/test/Transforms/LoopSimplify/pr30454.ll
new file mode 100644
index 00000000000..3dcc393aa81
--- /dev/null
+++ b/llvm/test/Transforms/LoopSimplify/pr30454.ll
@@ -0,0 +1,32 @@
+; RUN: opt < %s -lcssa -licm -S | FileCheck %s
+; PR30454
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i8 @bar()
+
+; Test that we preserve LCSSA form when removing edges from unreachable blocks.
+; CHECK-LABEL: @foo
+define void @foo() {
+entry:
+  br label %for.cond
+
+for.cond:
+  %x = phi i8 [ undef, %entry ], [ %y, %for.latch ]
+  br i1 undef, label %for.latch, label %exit
+
+; CHECK:      unreachable.bb:
+; CHECK-NEXT:   unreachable
+unreachable.bb:
+  br i1 undef, label %exit, label %for.latch
+
+for.latch:
+  %y = call i8 @bar()
+  br label %for.cond
+
+; CHECK:      exit:
+; CHECK-NEXT:   %x.lcssa = phi i8 [ %x, %for.cond ]
+exit:
+  %z = zext i8 %x to i32
+  ret void
+}