DeadArgumentElimination: keep return value on functions that have a live argument with the 'returned' attribute (rather than generate invalid IR); however, if both can be eliminated, both will be

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@185290 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 55 insertions, 0 deletions

diff --git a/test/Transforms/DeadArgElim/returned.ll b/test/Transforms/DeadArgElim/returned.ll
new file mode 100644
index 0000000000..c4d3ec7d3c
--- /dev/null
+++ b/test/Transforms/DeadArgElim/returned.ll
@@ -0,0 +1,55 @@
+; RUN: opt < %s -deadargelim -S | FileCheck %s
+
+%Ty = type { i32, i32 }
+
+; sanity check that the argument and return value are both dead
+; CHECK: define internal void @test1()
+
+define internal %Ty* @test1(%Ty* %this) {
+  ret %Ty* %this
+}
+
+; do not keep alive the return value of a function with a dead 'returned' argument
+; CHECK: define internal void @test2()
+
+define internal %Ty* @test2(%Ty* returned %this) {
+  ret %Ty* %this
+}
+
+; dummy to keep 'this' alive
+@dummy = global %Ty* null 
+
+; sanity check that return value is dead
+; CHECK: define internal void @test3(%Ty* %this)
+
+define internal %Ty* @test3(%Ty* %this) {
+  store volatile %Ty* %this, %Ty** @dummy
+  ret %Ty* %this
+}
+
+; keep alive return value of a function if the 'returned' argument is live
+; CHECK: define internal %Ty* @test4(%Ty* returned %this)
+
+define internal %Ty* @test4(%Ty* returned %this) {
+  store volatile %Ty* %this, %Ty** @dummy
+  ret %Ty* %this
+}
+
+; don't do this if 'returned' is on the call site...
+; CHECK: define internal void @test5(%Ty* %this)
+
+define internal %Ty* @test5(%Ty* %this) {
+  store volatile %Ty* %this, %Ty** @dummy
+  ret %Ty* %this
+}
+
+define %Ty* @caller(%Ty* %this) {
+  %1 = call %Ty* @test1(%Ty* %this)
+  %2 = call %Ty* @test2(%Ty* %this)
+  %3 = call %Ty* @test3(%Ty* %this)
+  %4 = call %Ty* @test4(%Ty* %this)
+; ...instead, drop 'returned' form the call site
+; CHECK: call void @test5(%Ty* %this)
+  %5 = call %Ty* @test5(%Ty* returned %this)
+  ret %Ty* %this
+}