[llvm-extract] Add option for recursive extraction

Summary:
Particularly, with --delete, this can be very useful for testing
new optimizations on some hotspots, without having to run it on the whole
application. E.g. as such:
```
llvm-extract app.bc --recursive --rfunc .*hotspot.* > hotspot.bc
llvm-extract app.bc --recursive --delete --rfunc .*hotspot.* > residual.bc
llc -filetype=obj residual.bc > residual.o
llc -filetype=obj hotspot.bc > hotspot.o
cc -o app residual.o hotspot.o
```

Reviewed By: davide
Differential Revision: https://reviews.llvm.org/D31722

llvm-svn: 299706

1 files changed, 32 insertions, 0 deletions

diff --git a/llvm/test/tools/llvm-extract/recursive.ll b/llvm/test/tools/llvm-extract/recursive.ll
new file mode 100644
index 00000000000..54813dba796
--- /dev/null
+++ b/llvm/test/tools/llvm-extract/recursive.ll
@@ -0,0 +1,32 @@
+; RUN: llvm-extract -func=a --recursive %s -S | FileCheck --check-prefix=CHECK-AB %s
+; RUN: llvm-extract -func=a --recursive --delete %s -S | FileCheck --check-prefix=CHECK-CD %s
+; RUN: llvm-extract -func=d --recursive %s -S | FileCheck --check-prefix=CHECK-CD %s
+
+; CHECK-AB: define void @a
+; CHECK-AB: define void @b
+; CHECK-AB-NOT: define void @c
+; CHECK-AB-NOT: define void @d
+
+; CHECK-CD-NOT: define void @a
+; CHECK-CD-NOT: define void @b
+; CHECK-CD: define void @c
+; CHECK-CD: define void @d
+
+define void @a() {
+  call void @b()
+  ret void
+}
+
+define void @b() {
+  ret void
+}
+
+define void @c() {
+  call void @d()
+  ret void
+}
+
+define void @d() {
+  call void @c()
+  ret void
+}