[Statepoint] Mark FixupStatepointCallerSaved as preserving the CFG

[craig.topper]

Summary

I can't find anything obvious in this pass that invalidates the CFG. So mark it as preserving so we stop rerunning some analysis passes.

I'm hoping this will restore some compile time lost by D75936 and D75937.

[skatkov]

You are right, CFG is not modified. Thank you for the change.

llvm/lib/CodeGen/FixupStatepointCallerSaved.cpp

 public:
   static char ID;
 
   FixupStatepointCallerSaved() : MachineFunctionPass(ID) {
     initializeFixupStatepointCallerSavedPass(*PassRegistry::getPassRegistry());
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
+    AU.setPreservesCFG();
     MachineFunctionPass::getAnalysisUsage(AU);
   }
 
   StringRef getPassName() const override {
     return "Fixup Statepoint Caller Saved";
   }
 
   bool runOnMachineFunction(MachineFunction &MF) override;

llvm/test/CodeGen/ARM/O3-pipeline.ll

 ; CHECK-NEXT:      Machine Optimization Remark Emitter
 ; CHECK-NEXT:      Greedy Register Allocator
 ; CHECK-NEXT:      Virtual Register Rewriter
 ; CHECK-NEXT:      Stack Slot Coloring
 ; CHECK-NEXT:      Machine Copy Propagation Pass
 ; CHECK-NEXT:      Machine Loop Invariant Code Motion
 ; CHECK-NEXT:      Fixup Statepoint Caller Saved
 ; CHECK-NEXT:      PostRA Machine Sink
-; CHECK-NEXT:      MachineDominator Tree Construction
-; CHECK-NEXT:      Machine Natural Loop Construction
 ; CHECK-NEXT:      Machine Block Frequency Analysis
+; CHECK-NEXT:      MachineDominator Tree Construction
 ; CHECK-NEXT:      MachinePostDominator Tree Construction
 ; CHECK-NEXT:      Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:      Machine Optimization Remark Emitter
 ; CHECK-NEXT:      Shrink Wrapping analysis
 ; CHECK-NEXT:      Prologue/Epilogue Insertion & Frame Finalization
 ; CHECK-NEXT:      Control Flow Optimizer
 ; CHECK-NEXT:      Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:      Tail Duplication

llvm/test/CodeGen/X86/O3-pipeline.ll

 ; CHECK-NEXT:       Machine Loop Invariant Code Motion
 ; CHECK-NEXT:       Bundle Machine CFG Edges
 ; CHECK-NEXT:       X86 FP Stackifier
 ; CHECK-NEXT:       MachineDominator Tree Construction
 ; CHECK-NEXT:       Machine Dominance Frontier Construction
 ; CHECK-NEXT:       X86 Load Value Injection (LVI) Load Hardening
 ; CHECK-NEXT:       Fixup Statepoint Caller Saved
 ; CHECK-NEXT:       PostRA Machine Sink
-; CHECK-NEXT:       MachineDominator Tree Construction
-; CHECK-NEXT:       Machine Natural Loop Construction
 ; CHECK-NEXT:       Machine Block Frequency Analysis
 ; CHECK-NEXT:       MachinePostDominator Tree Construction
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis
 ; CHECK-NEXT:       Machine Optimization Remark Emitter
 ; CHECK-NEXT:       Shrink Wrapping analysis
 ; CHECK-NEXT:       Prologue/Epilogue Insertion & Frame Finalization
 ; CHECK-NEXT:       Control Flow Optimizer
 ; CHECK-NEXT:       Lazy Machine Block Frequency Analysis