DAG: Provide access to Pass instance from SelectionDAG

[arsenm]

Summary

This allows accessing an analysis pass during lowering.

As asked about here: http://lists.llvm.org/pipermail/llvm-dev/2017-June/114067.html

[arsenm]

ping

[arsenm]

ping

[arsenm]

ping

[arsenm]

ping

[hfinkel]

As asked about here: http://lists.llvm.org/pipermail/llvm-dev/2017-June/114067.html

It does not look like there was any response to that message. I'll respond there.

[hfinkel]

LGTM

[arsenm]

r309991

include/llvm/CodeGen/SelectionDAG.h

 /// but is significantly more simple, powerful, and is a graph form instead of a
 /// linear form.
 ///
 class SelectionDAG {
   const TargetMachine &TM;
   const SelectionDAGTargetInfo *TSI = nullptr;
   const TargetLowering *TLI = nullptr;
   MachineFunction *MF;
+  Pass *SDAGISelPass = nullptr;
   LLVMContext *Context;
   CodeGenOpt::Level OptLevel;
 
   /// The function-level optimization remark emitter.  Used to emit remarks
   /// whenever manipulating the DAG.
   OptimizationRemarkEmitter *ORE;
 
   /// The starting token.

 
 public:
   explicit SelectionDAG(const TargetMachine &TM, CodeGenOpt::Level);
   SelectionDAG(const SelectionDAG &) = delete;
   SelectionDAG &operator=(const SelectionDAG &) = delete;
   ~SelectionDAG();
 
   /// Prepare this SelectionDAG to process code in the given MachineFunction.
-  void init(MachineFunction &NewMF, OptimizationRemarkEmitter &NewORE);
+  void init(MachineFunction &NewMF, OptimizationRemarkEmitter &NewORE,
+            Pass *PassPtr);
 
   /// Clear state and free memory necessary to make this
   /// SelectionDAG ready to process a new block.
   void clear();
 
   MachineFunction &getMachineFunction() const { return *MF; }
+  const Pass *getPass() const { return SDAGISelPass; }
+
   const DataLayout &getDataLayout() const { return MF->getDataLayout(); }
   const TargetMachine &getTarget() const { return TM; }
   const TargetSubtargetInfo &getSubtarget() const { return MF->getSubtarget(); }
   const TargetLowering &getTargetLoweringInfo() const { return *TLI; }
   const SelectionDAGTargetInfo &getSelectionDAGInfo() const { return *TSI; }
   LLVMContext *getContext() const {return Context; }
   OptimizationRemarkEmitter &getORE() const { return *ORE; }
 

lib/CodeGen/SelectionDAG/SelectionDAG.cpp

SelectionDAG::SelectionDAG(const TargetMachine &tm, CodeGenOpt::Level OL)
     : TM(tm), OptLevel(OL),
       EntryNode(ISD::EntryToken, 0, DebugLoc(), getVTList(MVT::Other)),
       Root(getEntryNode()) {
   InsertNode(&EntryNode);
   DbgInfo = new SDDbgInfo();
 }
 
 void SelectionDAG::init(MachineFunction &NewMF,
-                        OptimizationRemarkEmitter &NewORE) {
+                        OptimizationRemarkEmitter &NewORE,
+                        Pass *PassPtr) {
   MF = &NewMF;
+  SDAGISelPass = PassPtr;
   ORE = &NewORE;
   TLI = getSubtarget().getTargetLowering();
   TSI = getSubtarget().getSelectionDAGInfo();
   Context = &MF->getFunction()->getContext();
 }
 
 SelectionDAG::~SelectionDAG() {
   assert(!UpdateListeners && "Dangling registered DAGUpdateListeners");

lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

bool SelectionDAGISel::runOnMachineFunction(MachineFunction &mf) {
   DominatorTree *DT = DTWP ? &DTWP->getDomTree() : nullptr;
   auto *LIWP = getAnalysisIfAvailable<LoopInfoWrapperPass>();
   LoopInfo *LI = LIWP ? &LIWP->getLoopInfo() : nullptr;
 
   DEBUG(dbgs() << "\n\n\n=== " << Fn.getName() << "\n");
 
   SplitCriticalSideEffectEdges(const_cast<Function &>(Fn), DT, LI);
 
-  CurDAG->init(*MF, *ORE);
+  CurDAG->init(*MF, *ORE, this);
   FuncInfo->set(Fn, *MF, CurDAG);
 
   // Now get the optional analyzes if we want to.
   // This is based on the possibly changed OptLevel (after optnone is taken
   // into account).  That's unfortunate but OK because it just means we won't
   // ask for passes that have been required anyway.
 
   if (UseMBPI && OptLevel != CodeGenOpt::None)