Refactor code from inlining and globalopt that checks whether a function definition is unused, and enhance it so it can tell that functions which are only used by a blockaddress are in fact dead. This probably doesn't happen much on most code, but the Linux kernel's _THIS_IP_ can trigger this issue with blockaddress. (GlobalDCE can also handle the given tescase, but we only run that at -O3.) Found while looking at PR11180.

llvm-svn: 142572

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/test/Transforms/GlobalOpt/deadfunction.ll b/llvm/test/Transforms/GlobalOpt/deadfunction.ll
new file mode 100644
index 00000000000..5e003c63f77
--- /dev/null
+++ b/llvm/test/Transforms/GlobalOpt/deadfunction.ll
@@ -0,0 +1,27 @@
+; RUN: opt < %s -globalopt -S | FileCheck %s
+
+; CHECK-NOT: test
+
+declare void @aa()
+declare void @bb()
+
+; Test that we can erase a function which has a blockaddress referring to it
+@test.x = internal unnamed_addr constant [3 x i8*] [i8* blockaddress(@test, %a), i8* blockaddress(@test, %b), i8* blockaddress(@test, %c)], align 16
+define internal void @test(i32 %n) nounwind noinline {
+entry:
+  %idxprom = sext i32 %n to i64
+  %arrayidx = getelementptr inbounds [3 x i8*]* @test.x, i64 0, i64 %idxprom
+  %0 = load i8** %arrayidx, align 8
+  indirectbr i8* %0, [label %a, label %b, label %c]
+
+a:
+  tail call void @aa() nounwind
+  br label %b
+
+b:
+  tail call void @bb() nounwind
+  br label %c
+
+c:
+  ret void
+}