Constant fold switch inst when looking for trivial conditions to unswitch on.
Summary: Constant fold switch inst when looking for trivial conditions to unswitch on.
Reviewers: sanjoy, chenli, hfinkel, efriedma
Subscribers: llvm-commits, mzolotukhin
Differential Revision: https://reviews.llvm.org/D29037
llvm-svn: 293250
diff --git a/llvm/test/Transforms/LoopUnswitch/trivial-unswitch.ll b/llvm/test/Transforms/LoopUnswitch/trivial-unswitch.ll
index db33282..2def5b6 100644
--- a/llvm/test/Transforms/LoopUnswitch/trivial-unswitch.ll
+++ b/llvm/test/Transforms/LoopUnswitch/trivial-unswitch.ll
@@ -44,4 +44,48 @@
ret i32 0
}
-declare void @some_func() noreturn
\ No newline at end of file
+
+; We will not be able trivially unswitch on the SwitchInst, as its input
+; is a constant. However, since its a constant we should be able to figure
+; out that the switch can be folded into a unconditional branch to %continue.
+; Then we unswitch on the br inst in %continue.
+;
+; CHECK: define i32 @test2(
+; This is an indication that the loop has been unswitched on %cond1.
+; CHECK: br i1 %cond1, label %..split_crit_edge, label %.loop_exit.split_crit_edge
+
+; CHECK: ..split_crit_edge: ; preds = %0
+; CHECK: br label %.split
+
+; CHECK: .split: ; preds = %..split_crit_edge
+; CHECK: br label %loop_begin
+
+; CHECK: loop_begin: ; preds = %do_something, %.split
+; CHECK: switch i32
+
+; CHECK: continue: ; preds = %loop_begin
+; CHECK: %var_val = load i32, i32* %var
+; CHECK: br i1 true, label %do_something, label %loop_exit
+
+define i32 @test2(i32* %var, i1 %cond1) {
+ br label %loop_begin
+
+loop_begin:
+ switch i32 1, label %continue [
+ i32 0, label %loop_exit
+ i32 1, label %continue
+ ]
+
+continue:
+ %var_val = load i32, i32* %var
+ br i1 %cond1, label %do_something, label %loop_exit
+
+do_something:
+ call void @some_func() noreturn nounwind
+ br label %loop_begin
+
+loop_exit:
+ ret i32 0
+}
+
+declare void @some_func() noreturn