Add testcase that checks that DeadArgElim doesn't touch stuff it shouldn't touch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52540 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/DeadArgElim/keepalive.ll

@@ -0,0 +1,36 @@
+; RUN: llvm-as < %s | opt -deadargelim | llvm-dis > %t
+; RUN: cat %t | grep {define internal \{  \} @test}
+; RUN: cat %t | grep {define internal \{ i32 \} @test}
+; RUN: cat %t | grep {define internal \<\{ i32, i32 \}\> @test}
+
+; Check if the pass doesn't modify anything that doesn't need changing. We feed
+; an unused argument to each function to lure it into changing _something_ about
+; the function and then changing to much.
+
+
+; This checks if the struct retval isn't changed into a void
+define internal {  } @test(i32 %DEADARG1) {
+        ret {  } {  } 
+}
+
+; This checks if the struct retval isn't removed
+define internal {i32} @test1(i32 %DEADARG1) {
+        ret { i32 } { i32 1 } 
+}
+
+; This checks if the struct doesn't get non-packed
+define internal <{ i32, i32 }> @test2(i32 %DEADARG1) {
+        ret <{ i32, i32 }> <{ i32 1, i32 2 }>
+}
+
+; We use this external function to make sure the return values don't become dead
+declare void @user({  }, { i32 }, <{ i32, i32 }>)
+
+define void @caller() {
+        %A = call {  } @test(i32 0)
+        %B = call { i32 } @test1(i32 1)
+        %C = call <{ i32, i32 }> @test2(i32 2)
+        call void @user({  } %A, { i32 } %B, <{ i32, i32 }> %C)
+        ret void
+}
+