[Power9] Code Cleanup - Remove needsAggressiveScheduling()

As we already return true from needsAggressiveScheduling() for the most recent
hardware it would be cleaner to just return true for all PowerPC hardware.

Differential Revision: https://reviews.llvm.org/D48663

llvm-svn: 337488

llvm/lib/Target/PowerPC/PPCSubtarget.cpp

@@ -175,27 +175,8 @@ bool PPCSubtarget::hasLazyResolverStub(const GlobalValue *GV) const {
   return false;
 }
 
-// Embedded cores need aggressive scheduling (and some others also benefit).
-static bool needsAggressiveScheduling(unsigned Directive) {
-  switch (Directive) {
-  default: return false;
-  case PPC::DIR_440:
-  case PPC::DIR_A2:
-  case PPC::DIR_E500mc:
-  case PPC::DIR_E5500:
-  case PPC::DIR_PWR7:
-  case PPC::DIR_PWR8:
-  // FIXME: Same as P8 until POWER9 scheduling info is available
-  case PPC::DIR_PWR9:
-    return true;
-  }
-}
-
 bool PPCSubtarget::enableMachineScheduler() const {
-  // Enable MI scheduling for the embedded cores.
-  // FIXME: Enable this for all cores (some additional modeling
-  // may be necessary).
-  return needsAggressiveScheduling(DarwinDirective);
+  return true;
 }
 
 // This overrides the PostRAScheduler bit in the SchedModel for each CPU.
@@ -213,19 +194,19 @@ void PPCSubtarget::getCriticalPathRCs(RegClassVector &CriticalPathRCs) const {
 
 void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
                                        unsigned NumRegionInstrs) const {
-  if (needsAggressiveScheduling(DarwinDirective)) {
-    Policy.OnlyTopDown = false;
-    Policy.OnlyBottomUp = false;
-  }
-
+  // The GenericScheduler that we use defaults to scheduling bottom up only.
+  // We want to schedule from both the top and the bottom and so we set
+  // OnlyBottomUp to false.
+  // We want to do bi-directional scheduling since it provides a more balanced
+  // schedule leading to better performance.
+  Policy.OnlyBottomUp = false;
   // Spilling is generally expensive on all PPC cores, so always enable
   // register-pressure tracking.
   Policy.ShouldTrackPressure = true;
 }
 
 bool PPCSubtarget::useAA() const {
-  // Use AA during code generation for the embedded cores.
-  return needsAggressiveScheduling(DarwinDirective);
+  return true;
 }
 
 bool PPCSubtarget::enableSubRegLiveness() const {