[AArch64] Disable Pre-RA Scheduler for Neoverse V2

llvm/lib/Target/AArch64/AArch64Features.td

@@ -669,6 +669,9 @@ def FeatureExynosCheapAsMoveHandling : SubtargetFeature<"exynos-cheap-as-move",
     "HasExynosCheapAsMoveHandling", "true",
     "Use Exynos specific handling of cheap instructions">;
 
+def FeatureDisablePreRAScheduler : SubtargetFeature<"use-prera-scheduler",
+    "DisablePreRAScheduler", "true", "Disable scheduling before register allocation">;
+
 def FeaturePostRAScheduler : SubtargetFeature<"use-postra-scheduler",
     "UsePostRAScheduler", "true", "Schedule again after register allocation">;
 

llvm/lib/Target/AArch64/AArch64ISelLowering.cpp

@@ -1173,7 +1173,8 @@ AArch64TargetLowering::AArch64TargetLowering(const TargetMachine &TM,
 
   setStackPointerRegisterToSaveRestore(AArch64::SP);
 
-  setSchedulingPreference(Sched::Hybrid);
+  setSchedulingPreference(Subtarget->enableMachineScheduler() ? Sched::Hybrid
+                                                              : Sched::Source);
 
   EnableExtLdPromotion = true;
 

llvm/lib/Target/AArch64/AArch64Processors.td

@@ -540,6 +540,7 @@ def TuneNeoverseV2 : SubtargetFeature<"neoversev2", "ARMProcFamily", "NeoverseV2
                                       FeatureCmpBccFusion,
                                       FeatureFuseAdrpAdd,
                                       FeatureALULSLFast,
+                                      FeatureDisablePreRAScheduler,
                                       FeaturePostRAScheduler,
                                       FeatureEnableSelectOptimize,
                                       FeatureUseFixedOverScalableIfEqualCost,

llvm/lib/Target/AArch64/AArch64Subtarget.h

@@ -156,7 +156,9 @@ class AArch64Subtarget final : public AArch64GenSubtargetInfo {
   const LegalizerInfo *getLegalizerInfo() const override;
   const RegisterBankInfo *getRegBankInfo() const override;
   const Triple &getTargetTriple() const { return TargetTriple; }
-  bool enableMachineScheduler() const override { return true; }
+  bool enableMachineScheduler() const override {
+    return !disablePreRAScheduler();
+  }
   bool enablePostRAScheduler() const override { return usePostRAScheduler(); }
   bool enableSubRegLiveness() const override { return EnableSubregLiveness; }