Enable MI scheduling (and CodeGen AA) by default for embedded PPC cores

For embedded PPC cores (especially the A2 core), using the MI scheduler with AA
is far superior to the other scheduling options.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190558 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCISelLowering.cpp

@@ -556,7 +556,10 @@ PPCTargetLowering::PPCTargetLowering(PPCTargetMachine &TM)
 
   setInsertFencesForAtomic(true);
 
-  setSchedulingPreference(Sched::Hybrid);
+  if (Subtarget->enableMachineScheduler())
+    setSchedulingPreference(Sched::Source);
+  else
+    setSchedulingPreference(Sched::Hybrid);
 
   computeRegisterProperties();
 
@@ -7853,7 +7856,7 @@ bool PPCTargetLowering::isFMAFasterThanFMulAndFAdd(EVT VT) const {
 }
 
 Sched::Preference PPCTargetLowering::getSchedulingPreference(SDNode *N) const {
-  if (DisableILPPref)
+  if (DisableILPPref || PPCSubTarget.enableMachineScheduler())
     return TargetLowering::getSchedulingPreference(N);
 
   return Sched::ILP;

lib/Target/PowerPC/PPCSubtarget.cpp

@@ -15,6 +15,7 @@
 #include "PPC.h"
 #include "PPCRegisterInfo.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineScheduler.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/Function.h"
@@ -186,3 +187,41 @@ bool PPCSubtarget::enablePostRAScheduler(
   return OptLevel >= CodeGenOpt::Default;
 }
 
+// Embedded cores need aggressive scheduling.
+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:
+    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);
+}
+
+void PPCSubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
+                                       MachineInstr *begin,
+                                       MachineInstr *end,
+                                       unsigned NumRegionInstrs) const {
+  if (needsAggressiveScheduling(DarwinDirective)) {
+    Policy.OnlyTopDown = false;
+    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);
+}
+

lib/Target/PowerPC/PPCSubtarget.h

@@ -207,6 +207,14 @@ public:
   bool enablePostRAScheduler(CodeGenOpt::Level OptLevel,
                              TargetSubtargetInfo::AntiDepBreakMode& Mode,
                              RegClassVector& CriticalPathRCs) const;
+
+  // Scheduling customization.
+  bool enableMachineScheduler() const;
+  void overrideSchedPolicy(MachineSchedPolicy &Policy,
+                           MachineInstr *begin,
+                           MachineInstr *end,
+                           unsigned NumRegionInstrs) const;
+  bool useAA() const;
 };
 } // End llvm namespace