[RegBankSelect] Use frequency and probability information to compute

more precise cost in Greedy mode.

In Fast mode the cost is irrelevant so do not bother requiring that
those passes get scheduled.

llvm-svn: 270244

llvm/include/llvm/CodeGen/GlobalISel/RegBankSelect.h

@@ -71,6 +71,8 @@
 namespace llvm {
 // Forward declarations.
 class BlockFrequency;
+class MachineBranchProbabilityInfo;
+class MachineBlockFrequencyInfo;
 class MachineRegisterInfo;
 class TargetRegisterInfo;
 
@@ -460,6 +462,14 @@ private:
   /// Information on the register classes for the current function.
   const TargetRegisterInfo *TRI;
 
+  /// Get the frequency of blocks.
+  /// This is required for non-fast mode.
+  MachineBlockFrequencyInfo *MBFI;
+
+  /// Get the frequency of the edges.
+  /// This is required for non-fast mode.
+  MachineBranchProbabilityInfo *MBPI;
+
   /// Helper class used for every code morphing.
   MachineIRBuilder MIRBuilder;
 
@@ -555,6 +565,8 @@ public:
     return "RegBankSelect";
   }
 
+  void getAnalysisUsage(AnalysisUsage &AU) const override;
+
   /// Walk through \p MF and assign a register bank to every virtual register
   /// that are still mapped to nothing.
   /// The target needs to provide a RegisterBankInfo and in particular

llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp

@@ -26,13 +26,18 @@
 using namespace llvm;
 
 char RegBankSelect::ID = 0;
-INITIALIZE_PASS(RegBankSelect, "regbankselect",
-                "Assign register bank of generic virtual registers",
-                false, false);
+INITIALIZE_PASS_BEGIN(RegBankSelect, "regbankselect",
+                      "Assign register bank of generic virtual registers",
+                      false, false);
+INITIALIZE_PASS_DEPENDENCY(MachineBlockFrequencyInfo)
+INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
+INITIALIZE_PASS_END(RegBankSelect, "regbankselect",
+                    "Assign register bank of generic virtual registers", false,
+                    false);
 
 RegBankSelect::RegBankSelect(Mode RunningMode)
-    : MachineFunctionPass(ID), RBI(nullptr), MRI(nullptr),
-      OptMode(RunningMode) {
+    : MachineFunctionPass(ID), RBI(nullptr), MRI(nullptr), TRI(nullptr),
+      MBFI(nullptr), MBPI(nullptr), OptMode(RunningMode) {
   initializeRegBankSelectPass(*PassRegistry::getPassRegistry());
 }
 
@@ -41,10 +46,26 @@ void RegBankSelect::init(MachineFunction &MF) {
   assert(RBI && "Cannot work without RegisterBankInfo");
   MRI = &MF.getRegInfo();
   TRI = MF.getSubtarget().getRegisterInfo();
-  assert(OptMode == Mode::Fast && "Non-fast mode not implemented");
+  if (OptMode != Mode::Fast) {
+    MBFI = &getAnalysis<MachineBlockFrequencyInfo>();
+    MBPI = &getAnalysis<MachineBranchProbabilityInfo>();
+  } else {
+    MBFI = nullptr;
+    MBPI = nullptr;
+  }
   MIRBuilder.setMF(MF);
 }
 
+void RegBankSelect::getAnalysisUsage(AnalysisUsage &AU) const {
+  if (OptMode != Mode::Fast) {
+    // We could preserve the information from these two analysis but
+    // the APIs do not allow to do so yet.
+    AU.addRequired<MachineBlockFrequencyInfo>();
+    AU.addRequired<MachineBranchProbabilityInfo>();
+  }
+  MachineFunctionPass::getAnalysisUsage(AU);
+}
+
 bool RegBankSelect::assignmentMatch(
     unsigned Reg, const RegisterBankInfo::ValueMapping &ValMapping,
     bool &OnlyAssign) const {
@@ -273,7 +294,7 @@ RegBankSelect::MappingCost RegBankSelect::computeMapping(
     SmallVectorImpl<RepairingPlacement> &RepairPts) {
 
   // If mapped with InstrMapping, MI will have the recorded cost.
-  MappingCost Cost(1);
+  MappingCost Cost(MBFI ? MBFI->getBlockFreq(MI.getParent()) : 1);
   bool Saturated = Cost.addLocalCost(InstrMapping.getCost());
   assert(!Saturated && "Possible mapping saturated the cost");
   DEBUG(dbgs() << "Evaluating mapping cost for: " << MI);