add a new @llvm.donothing intrinsic that, well, does nothing, and teach CodeGen to ignore calls to it

llvm-svn: 159383

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Generic/donothing.ll b/llvm/test/CodeGen/Generic/donothing.ll
new file mode 100644
index 00000000000..d6ba138fc6d
--- /dev/null
+++ b/llvm/test/CodeGen/Generic/donothing.ll
@@ -0,0 +1,31 @@
+; RUN: llc < %s | FileCheck %s
+
+declare i32 @__gxx_personality_v0(...)
+declare void @__cxa_call_unexpected(i8*)
+declare void @llvm.donothing() readnone
+
+; CHECK: f1
+define void @f1() nounwind uwtable ssp {
+entry:
+; CHECK-NOT donothing
+  invoke void @llvm.donothing()
+  to label %invoke.cont unwind label %lpad
+
+invoke.cont:
+  ret void
+
+lpad:
+  %0 = landingpad { i8*, i32 } personality i8* bitcast (i32 (...)* @__gxx_personality_v0 to i8*)
+          filter [0 x i8*] zeroinitializer
+  %1 = extractvalue { i8*, i32 } %0, 0
+  tail call void @__cxa_call_unexpected(i8* %1) noreturn nounwind
+  unreachable
+}
+
+; CHECK: f2
+define void @f2() nounwind {
+entry:
+; CHECK-NOT donothing
+  call void @llvm.donothing()
+  ret void
+}