Enable tail calls on ARM by default, with some

basic tests.

This has been well tested on Darwin but not elsewhere.
It should work provided the linker correctly resolves
  B.W  <label in other function>
which it has not seen before, at least from llvm-based
compilers.  I'm leaving the arm-tail-calls switch in
until I see if there's any problems because of that;
it might need to be disabled for some environments.

llvm-svn: 106299

1 files changed, 27 insertions, 0 deletions

diff --git a/llvm/test/CodeGen/Thumb2/thumb2-call-tc.ll b/llvm/test/CodeGen/Thumb2/thumb2-call-tc.ll
new file mode 100644
index 00000000000..d31ae0cc455
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb2/thumb2-call-tc.ll
@@ -0,0 +1,27 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-darwin -mattr=+thumb2 | FileCheck %s -check-prefix=DARWIN
+; RUN: llc < %s -mtriple=thumbv7-linux -mattr=+thumb2 | FileCheck %s -check-prefix=LINUX
+
+@t = weak global i32 ()* null           ; <i32 ()**> [#uses=1]
+
+declare void @g(i32, i32, i32, i32)
+
+define void @f() {
+; DARWIN: f:
+; DARWIN: blx _g
+
+; LINUX: f:
+; LINUX: bl g
+        call void @g( i32 1, i32 2, i32 3, i32 4 )
+        ret void
+}
+
+define void @h() {
+; DARWIN: h:
+; DARWIN: bx r0 @ TAILCALL
+
+; LINUX: h:
+; LINUX: bx r0 @ TAILCALL
+        %tmp = load i32 ()** @t         ; <i32 ()*> [#uses=1]
+        %tmp.upgrd.2 = tail call i32 %tmp( )            ; <i32> [#uses=0]
+        ret void
+}