Don't spill PPC VRSAVE on non-Darwin (even in SjLj)

As Bill Schmidt pointed out to me, only on Darwin do we need to spill/restore
VRSAVE in the SjLj code. For non-Darwin, don't spill/restore VRSAVE (and I've
added some asserts to make sure that we're not).

As it turns out, we're not currently handling the Darwin case correctly (I've
added a FIXME in the test case). I've tried adding various implied register
definitions/uses to force the spill without success, so I'll need to address
this later.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178096 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCInstrInfo.cpp b/lib/Target/PowerPC/PPCInstrInfo.cpp
index 2be8df9..1558856 100644
--- a/lib/Target/PowerPC/PPCInstrInfo.cpp
+++ b/lib/Target/PowerPC/PPCInstrInfo.cpp
@@ -509,6 +509,8 @@
                                        FrameIdx));
     NonRI = true;
   } else if (PPC::VRSAVERCRegClass.hasSubClassEq(RC)) {
+    assert(TM.getSubtargetImpl()->isDarwin() &&
+           "VRSAVE only needs spill/restore on Darwin");
     NewMIs.push_back(addFrameReference(BuildMI(MF, DL, get(PPC::SPILL_VRSAVE))
                                        .addReg(SrcReg,
                                                getKillRegState(isKill)),
@@ -627,6 +629,8 @@
                                        FrameIdx));
     NonRI = true;
   } else if (PPC::VRSAVERCRegClass.hasSubClassEq(RC)) {
+    assert(TM.getSubtargetImpl()->isDarwin() &&
+           "VRSAVE only needs spill/restore on Darwin");
     NewMIs.push_back(addFrameReference(BuildMI(MF, DL,
                                                get(PPC::RESTORE_VRSAVE),
                                                DestReg),