[PowerPC] Rename DarwinDirective to CPUDirective (NFC)

Summary:
This patch renames the DarwinDirective (used to identify which CPU was defined)
to CPUDirective. It also adds the getCPUDirective() method and replaces all uses
of getDarwinDirective() with getCPUDirective().

Once this patch lands and downstream users of the getDarwinDirective() method
have switched to the getCPUDirective() method, the old getDarwinDirective()
method will be removed.

Reviewers: nemanjai, hfinkel, power-llvm-team, jsji, echristo, #powerpc, jhibbits

Reviewed By: hfinkel, jsji, jhibbits

Subscribers: hiraditya, shchenz, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70352
diff --git a/llvm/lib/Target/PowerPC/PPCHazardRecognizers.cpp b/llvm/lib/Target/PowerPC/PPCHazardRecognizers.cpp
index 391ebcc..ffaa3e0 100644
--- a/llvm/lib/Target/PowerPC/PPCHazardRecognizers.cpp
+++ b/llvm/lib/Target/PowerPC/PPCHazardRecognizers.cpp
@@ -158,7 +158,7 @@
   // new group.
   if (isLoadAfterStore(SU) && CurSlots < 6) {
     unsigned Directive =
-        DAG->MF.getSubtarget<PPCSubtarget>().getDarwinDirective();
+        DAG->MF.getSubtarget<PPCSubtarget>().getCPUDirective();
     // If we're using a special group-terminating nop, then we need only one.
     // FIXME: the same for P9 as previous gen until POWER9 scheduling is ready
     if (Directive == PPC::DIR_PWR6 || Directive == PPC::DIR_PWR7 ||
@@ -218,7 +218,7 @@
 
 void PPCDispatchGroupSBHazardRecognizer::EmitNoop() {
   unsigned Directive =
-      DAG->MF.getSubtarget<PPCSubtarget>().getDarwinDirective();
+      DAG->MF.getSubtarget<PPCSubtarget>().getCPUDirective();
   // If the group has now filled all of its slots, or if we're using a special
   // group-terminating nop, the group is complete.
   // FIXME: the same for P9 as previous gen until POWER9 scheduling is ready