ARM: R9 is not safe to use for tcGPR.

Indirect tail-calls shouldn't use R9 for the branch destination, as
it's not reliably a call-clobbered register.

rdar://14793425

llvm-svn: 188967

2 files changed, 15 insertions, 1 deletions

diff --git a/llvm/lib/Target/ARM/ARMRegisterInfo.td b/llvm/lib/Target/ARM/ARMRegisterInfo.td
index bb7d358ff18..90c6a965acf 100644
--- a/llvm/lib/Target/ARM/ARMRegisterInfo.td
+++ b/llvm/lib/Target/ARM/ARMRegisterInfo.td
@@ -251,7 +251,7 @@ def hGPR : RegisterClass<"ARM", [i32], 32, (sub GPR, tGPR)>;
 // to the saved value before the tail call, which would clobber a call address.
 // Note, getMinimalPhysRegClass(R0) returns tGPR because of the names of
 // this class and the preceding one(!)  This is what we want.
-def tcGPR : RegisterClass<"ARM", [i32], 32, (add R0, R1, R2, R3, R9, R12)> {
+def tcGPR : RegisterClass<"ARM", [i32], 32, (add R0, R1, R2, R3, R12)> {
   let AltOrders = [(and tcGPR, tGPR)];
   let AltOrderSelect = [{
       return MF.getTarget().getSubtarget<ARMSubtarget>().isThumb1Only();
diff --git a/llvm/test/CodeGen/Thumb2/tail-call-r9.ll b/llvm/test/CodeGen/Thumb2/tail-call-r9.ll
new file mode 100644
index 00000000000..24c76c98c03
--- /dev/null
+++ b/llvm/test/CodeGen/Thumb2/tail-call-r9.ll
@@ -0,0 +1,14 @@
+; RUN: llc < %s -mtriple=thumbv7-apple-ios -mcpu=cortex-m3 | FileCheck %s
+
+@foo = common global void ()* null, align 4
+
+; Make sure in the presence of a tail call, r9 doesn't get used to hold
+; the destination address. It's callee-saved in AAPCS.
+define arm_aapcscc void @test(i32 %a) nounwind {
+; CHECK-LABEL: test:
+; CHECK-NOT bx r9
+  %tmp = load void ()** @foo, align 4
+  tail call void asm sideeffect "", "~{r0},~{r1},~{r2},~{r3},~{r12}"() nounwind
+  tail call arm_aapcscc void %tmp() nounwind
+  ret void
+}