1 files changed, 66 insertions, 0 deletions
diff --git a/llvm/test/Transforms/JumpThreading/phi-known.ll b/llvm/test/Transforms/JumpThreading/phi-known.ll
new file mode 100644
index 00000000000..8eaf57f748a
--- /dev/null
+++ b/llvm/test/Transforms/JumpThreading/phi-known.ll
@@ -0,0 +1,66 @@
+; RUN: opt -S -jump-threading %s | FileCheck %s
+
+; Value of predicate known on all inputs (trivial case)
+; Note: InstCombine/EarlyCSE would also get this case
+define void @test(i8* %p, i8** %addr) {
+; CHECK-LABEL: @test
+entry:
+  %cmp0 = icmp eq i8* %p, null
+  br i1 %cmp0, label %exit, label %loop
+loop:
+; CHECK-LABEL: loop:
+; CHECK-NEXT: phi
+; CHECK-NEXT: br label %loop
+  %p1 = phi i8* [%p, %entry], [%p1, %loop]
+  %cmp1 = icmp eq i8* %p1, null
+  br i1 %cmp1, label %exit, label %loop
+exit:
+  ret void
+}
+
+; Value of predicate known on all inputs (non-trivial)
+define void @test2(i8* %p) {
+; CHECK-LABEL: @test2
+entry:
+  %cmp0 = icmp eq i8* %p, null
+  br i1 %cmp0, label %exit, label %loop
+loop:
+  %p1 = phi i8* [%p, %entry], [%p2, %backedge]
+  %cmp1 = icmp eq i8* %p1, null
+  br i1 %cmp1, label %exit, label %backedge
+backedge:
+; CHECK-LABEL: backedge:
+; CHECK-NEXT: phi
+; CHECK-NEXT: bitcast
+; CHECK-NEXT: load
+; CHECK-NEXT: cmp
+; CHECK-NEXT: br 
+; CHECK-DAG: label %backedge
+  %addr = bitcast i8* %p1 to i8**
+  %p2 = load i8*, i8** %addr
+  %cmp2 = icmp eq i8* %p2, null
+  br i1 %cmp2, label %exit, label %loop
+exit:
+  ret void
+}
+
+; If the inputs don't branch the same way, we can't rewrite
+; Well, we could unroll this loop exactly twice, but that's
+; a different transform.
+define void @test_mixed(i8* %p) {
+; CHECK-LABEL: @test_mixed
+entry:
+  %cmp0 = icmp eq i8* %p, null
+  br i1 %cmp0, label %exit, label %loop
+loop:
+; CHECK-LABEL: loop:
+; CHECK-NEXT: phi
+; CHECK-NEXT: %cmp1 = icmp
+; CHECK-NEXT: br i1 %cmp1
+  %p1 = phi i8* [%p, %entry], [%p1, %loop]
+  %cmp1 = icmp ne i8* %p1, null
+  br i1 %cmp1, label %exit, label %loop
+exit:
+  ret void
+}
+