[LLC][MIPS] Fix crash after enabling LLVM_ENABLE_EXPENSIVE_CHECKS

[nitesh.jain]

Summary

With the LLVM_ENABLE_EXPENSIVE_CHECKS enabled, following sequence of passes are executed:

 …
Dominator Tree Construction
Basic Alias Analysis (stateless AA impl)
Function Alias Analysis Results
Natural Loop Information
Branch Probability Analysis
MIPS DAG->DAG Pattern Instruction Selection
Branch Probability Analysis
MIPS DAG->DAG Pattern Instruction Selection
Expand ISel Pseudo-instructions
Tail Duplication
 ….

The Dominator tree is the indirect require dependency of "MIPS DAG->DAG Pattern Instruction Selection" pass. The dominator tree construction pass is freed before the second pass of "MIPS DAG->DAG Pattern Instruction Selection". This causes code to crash when it verify the preserved analysis after the second pass is executed

[sdardis]

LGTM.

lib/Target/Mips/MipsSEISelDAGToDAG.cpp

35

This include should come after: #include "llvm/IR/CFG.h"

[nitesh.jain]

Update Diff as per suggestion.

lib/Target/Mips/MipsSEISelDAGToDAG.h

 public:
   explicit MipsSEDAGToDAGISel(MipsTargetMachine &TM, CodeGenOpt::Level OL)
       : MipsDAGToDAGISel(TM, OL) {}
 
 private:
 
   bool runOnMachineFunction(MachineFunction &MF) override;
 
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
   void addDSPCtrlRegOperands(bool IsDef, MachineInstr &MI,
                              MachineFunction &MF);
 
   unsigned getMSACtrlReg(const SDValue RegIdx) const;
 
   bool replaceUsesWithZeroReg(MachineRegisterInfo *MRI, const MachineInstr&);
 
   std::pair<SDNode *, SDNode *> selectMULT(SDNode *N, unsigned Opc,

lib/Target/Mips/MipsSEISelDAGToDAG.cpp

 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Intrinsics.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/IR/Dominators.h"
 using namespace llvm;
 
 #define DEBUG_TYPE "mips-isel"
 
 bool MipsSEDAGToDAGISel::runOnMachineFunction(MachineFunction &MF) {
   Subtarget = &static_cast<const MipsSubtarget &>(MF.getSubtarget());
   if (Subtarget->inMips16Mode())
     return false;
   return MipsDAGToDAGISel::runOnMachineFunction(MF);
 }
 
+void MipsSEDAGToDAGISel::getAnalysisUsage(AnalysisUsage &AU) const {
+  AU.addRequired<DominatorTreeWrapperPass>();
+  SelectionDAGISel::getAnalysisUsage(AU);
+}
+
 void MipsSEDAGToDAGISel::addDSPCtrlRegOperands(bool IsDef, MachineInstr &MI,
                                                MachineFunction &MF) {
   MachineInstrBuilder MIB(MF, &MI);
   unsigned Mask = MI.getOperand(1).getImm();
   unsigned Flag =
       IsDef ? RegState::ImplicitDefine : RegState::Implicit | RegState::Undef;
 
   if (Mask & 1)