ARM: use r7 as the frame-pointer on all MachO targets.

This is better for a few reasons:
  + It matches the other tooling for iOS.
  + It matches EABI in more cases (i.e. Thumb-mode, and in practice we don't
    use ARM mode).
  + It leads to infinitesimally smaller code (0.2%, yay!).

rdar://25369506

llvm-svn: 266003
diff --git a/llvm/test/CodeGen/ARM/interrupt-attr.ll b/llvm/test/CodeGen/ARM/interrupt-attr.ll
index 43bd581..794f672 100644
--- a/llvm/test/CodeGen/ARM/interrupt-attr.ll
+++ b/llvm/test/CodeGen/ARM/interrupt-attr.ll
@@ -35,15 +35,15 @@
   ; Normal AAPCS function (r0-r3 pushed onto stack by hardware, lr set to
   ; appropriate sentinel so no special return needed).
 ; CHECK-M-LABEL: irq_fn:
-; CHECK-M: push.w {r4, r7, r11, lr}
-; CHECK-M: add.w r11, sp, #8
+; CHECK-M: push {r4, r6, r7, lr}
+; CHECK-M: add r7, sp, #8
 ; CHECK-M: mov r4, sp
 ; CHECK-M: bfc r4, #0, #3
 ; CHECK-M: mov sp, r4
 ; CHECK-M: bl _bar
-; CHECK-M: sub.w r4, r11, #8
+; CHECK-M: sub.w r4, r7, #8
 ; CHECK-M: mov sp, r4
-; CHECK-M: pop.w {r4, r7, r11, pc}
+; CHECK-M: pop {r4, r6, r7, pc}
 
   call arm_aapcscc void @bar()
   ret void