implement a transformation in jump threading that is currently
done by condprop, but do it in a much more general form. The
basic idea is that we can do a limited form of tail duplication
in the case when we have a branch on a phi. Moving the branch
up in to the predecessor block makes instruction selection
much easier and encourages chained jump threadings.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@83759 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Transforms/JumpThreading/basic.ll b/test/Transforms/JumpThreading/basic.ll
index cab7712..50433db 100644
--- a/test/Transforms/JumpThreading/basic.ll
+++ b/test/Transforms/JumpThreading/basic.ll
@@ -105,3 +105,37 @@
ret i32 %B
}
+
+;; This tests that the branch in 'merge' can be cloned up into T1.
+define i32 @test5(i1 %cond, i1 %cond2) {
+; CHECK: @test5
+
+ br i1 %cond, label %T1, label %F1
+
+T1:
+; CHECK: T1:
+; CHECK-NEXT: %v1 = call i32 @f1()
+; CHECK-NEXT: %cond3 = icmp eq i32 %v1, 412
+; CHECK-NEXT: br i1 %cond3, label %T2, label %F2
+
+ %v1 = call i32 @f1()
+ %cond3 = icmp eq i32 %v1, 412
+ br label %Merge
+
+F1:
+ %v2 = call i32 @f2()
+ br label %Merge
+
+Merge:
+ %A = phi i1 [%cond3, %T1], [%cond2, %F1]
+ %B = phi i32 [%v1, %T1], [%v2, %F1]
+ br i1 %A, label %T2, label %F2
+
+T2:
+ call void @f3()
+ ret i32 %B
+
+F2:
+ ret i32 %B
+}
+