Commit the new DeadArgElim pass again, this time with the gcc bootstrap failures fixed.

Also add a testcase to reproduce the gcc bootstrap failure in very much reduced form.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@52677 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/DeadArgElim/2008-06-23-DeadAfterLive.ll

@@ -0,0 +1,23 @@
+; RUN: llvm-as < %s | opt -deadargelim -die | llvm-dis > %t
+; RUN: cat %t | grep 123
+
+; This test tries to catch wrongful removal of return values for a specific case
+; that was break llvm-gcc builds.
+
+; This function has a live return value, it is used by @alive.
+define internal i32 @test5() {
+  ret i32 123 
+}
+
+; This function doesn't use the return value @test5 and tries to lure DAE into
+; marking @test5's return value dead because only this call is unused.
+define i32 @dead() {
+  %DEAD = call i32 @test5()
+  ret i32 0
+}
+
+; This function ensures the retval of @test5 is live.
+define i32 @alive() {
+  %LIVE = call i32 @test5()
+  ret i32 %LIVE
+}

test/Transforms/DeadArgElim/deadretval2.ll

@@ -1,4 +1,6 @@
-; RUN: llvm-as < %s | opt -deadargelim -die | llvm-dis | not grep DEAD
+; RUN: llvm-as < %s | opt -deadargelim -die | llvm-dis > %t
+; RUN: cat %t | not grep DEAD
+; RUN: cat %t | grep LIVE | count 4
 
 @P = external global i32                ; <i32*> [#uses=1]
 
@@ -31,3 +33,27 @@ define void @test4() {
         %DEAD2 = call i32 @id( i32 %DEAD )              ; <i32> [#uses=0]
         ret void
 }
+
+; These test if returning another functions return value properly marks that
+; other function's return value as live. We do this twice, with the functions in
+; different orders (ie, first the caller, than the callee and first the callee
+; and then the caller) since DAE processes functions one by one and handles
+; these cases slightly different.
+
+define internal i32 @test5() {
+  ret i32 123 
+}
+
+define i32 @test6() {
+  %LIVE = call i32 @test5()
+  ret i32 %LIVE
+}
+
+define i32 @test7() {
+  %LIVE = call i32 @test8()
+  ret i32 %LIVE
+}
+
+define internal i32 @test8() {
+  ret i32 124
+}

test/Transforms/DeadArgElim/multdeadretval.ll

@@ -0,0 +1,39 @@
+; This test sees if return values (and arguments) are properly removed when they
+; are unused. All unused values are typed i16, so we can easily check. We also
+; run instcombine to fold insert/extractvalue chains and we run dce to clean up
+; any remaining dead stuff.
+; RUN: llvm-as < %s | opt -deadargelim -instcombine -dce | llvm-dis | not grep i16
+
+define internal {i16, i32} @test(i16 %DEADARG) {
+        %A = insertvalue {i16,i32} undef, i16 1, 0
+        %B = insertvalue {i16,i32} %A, i32 1001, 1
+        ret {i16,i32} %B
+}
+
+define internal {i32, i16} @test2() {
+        %DEAD = call i16 @test4()
+        %A = insertvalue {i32,i16} undef, i32 1, 0
+        %B = insertvalue {i32,i16} %A, i16 %DEAD, 1
+        ret {i32,i16} %B
+}
+
+define internal i32 @test3(i16 %A) {
+        %ret = call {i16, i32} @test( i16 %A )                ; <i32> [#uses=0]
+        %DEAD = extractvalue {i16, i32} %ret, 0
+        %LIVE = extractvalue {i16, i32} %ret, 1
+        ret i32 %LIVE
+}
+
+define internal i16 @test4() {
+        ret i16 0
+}
+
+define i32 @main() {
+        %ret = call {i32, i16} @test2()                ; <i32> [#uses=1]
+        %LIVE = extractvalue {i32, i16} %ret, 0
+        %DEAD = extractvalue {i32, i16} %ret, 1
+        %Y = add i32 %LIVE, -123           ; <i32> [#uses=1]
+        %LIVE2 = call i32 @test3(i16 %DEAD)                ; <i32> [#uses=1]
+        %Z = add i32 %LIVE2, %Y           ; <i32> [#uses=1]
+        ret i32 %Z
+}