[RegisterBankInfo] Cache the getMinimalPhysRegClass information

TargetRegisterInfo::getMinimalPhysRegClass is actually pretty expensive
because it has to iterate over all the register classes.
Cache this information as we need and get it so that we limit its usage.
Right now, we heavily rely on it, because this is how we get the mapping
for vregs defined by copies from physreg (i.e., the one that are ABI
related).

Improve compile time by up to 10% for that pass.

NFC

llvm-svn: 315759

3 files changed, 32 insertions, 10 deletions

diff --git a/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h b/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
index 60905c7ec22..02868b22098 100644
--- a/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
+++ b/llvm/include/llvm/CodeGen/GlobalISel/RegisterBankInfo.h
@@ -407,6 +407,10 @@ protected:
   mutable DenseMap<unsigned, std::unique_ptr<const InstructionMapping>>
       MapOfInstructionMappings;
 
+  /// Getting the minimal register class of a physreg is expensive.
+  /// Cache this information as we get it.
+  mutable DenseMap<unsigned, const TargetRegisterClass *> PhysRegMinimalRCs;
+
   /// Create a RegisterBankInfo that can accommodate up to \p NumRegBanks
   /// RegisterBank instances.
   RegisterBankInfo(RegisterBank **RegBanks, unsigned NumRegBanks);
@@ -427,6 +431,11 @@ protected:
     return *RegBanks[ID];
   }
 
+  /// Get the MinimalPhysRegClass for Reg.
+  /// \pre Reg is a physical register.
+  const TargetRegisterClass &
+  getMinimalPhysRegClass(unsigned Reg, const TargetRegisterInfo &TRI) const;
+
   /// Try to get the mapping of \p MI.
   /// See getInstrMapping for more details on what a mapping represents.
   ///
@@ -699,8 +708,8 @@ public:
   /// virtual register.
   ///
   /// \pre \p Reg != 0 (NoRegister).
-  static unsigned getSizeInBits(unsigned Reg, const MachineRegisterInfo &MRI,
-                                const TargetRegisterInfo &TRI);
+  unsigned getSizeInBits(unsigned Reg, const MachineRegisterInfo &MRI,
+                         const TargetRegisterInfo &TRI) const;
 
   /// Check that information hold by this instance make sense for the
   /// given \p TRI.
diff --git a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
index f2eb217c0b8..fac26a16412 100644
--- a/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegBankSelect.cpp
@@ -221,9 +221,8 @@ uint64_t RegBankSelect::getRepairCost(
     // into a new virtual register.
     // We would also need to propagate this information in the
     // repairing placement.
-    unsigned Cost =
-        RBI->copyCost(*DesiredRegBrank, *CurRegBank,
-                      RegisterBankInfo::getSizeInBits(MO.getReg(), *MRI, *TRI));
+    unsigned Cost = RBI->copyCost(*DesiredRegBrank, *CurRegBank,
+                                  RBI->getSizeInBits(MO.getReg(), *MRI, *TRI));
     // TODO: use a dedicated constant for ImpossibleCost.
     if (Cost != std::numeric_limits<unsigned>::max())
       return Cost;
diff --git a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
index 3d7132717cc..cad1bd68adf 100644
--- a/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
+++ b/llvm/lib/CodeGen/GlobalISel/RegisterBankInfo.cpp
@@ -84,7 +84,7 @@ const RegisterBank *
 RegisterBankInfo::getRegBank(unsigned Reg, const MachineRegisterInfo &MRI,
                              const TargetRegisterInfo &TRI) const {
   if (TargetRegisterInfo::isPhysicalRegister(Reg))
-    return &getRegBankFromRegClass(*TRI.getMinimalPhysRegClass(Reg));
+    return &getRegBankFromRegClass(getMinimalPhysRegClass(Reg, TRI));
 
   assert(Reg && "NoRegister does not have a register bank");
   const RegClassOrRegBank &RegClassOrBank = MRI.getRegClassOrRegBank(Reg);
@@ -95,6 +95,19 @@ RegisterBankInfo::getRegBank(unsigned Reg, const MachineRegisterInfo &MRI,
   return nullptr;
 }
 
+const TargetRegisterClass &
+RegisterBankInfo::getMinimalPhysRegClass(unsigned Reg,
+                                         const TargetRegisterInfo &TRI) const {
+  assert(TargetRegisterInfo::isPhysicalRegister(Reg) &&
+         "Reg must be a physreg");
+  const auto &RegRCIt = PhysRegMinimalRCs.find(Reg);
+  if (RegRCIt != PhysRegMinimalRCs.end())
+    return *RegRCIt->second;
+  const TargetRegisterClass *PhysRC = TRI.getMinimalPhysRegClass(Reg);
+  PhysRegMinimalRCs[Reg] = PhysRC;
+  return *PhysRC;
+}
+
 const RegisterBank *RegisterBankInfo::getRegBankFromConstraints(
     const MachineInstr &MI, unsigned OpIdx, const TargetInstrInfo &TII,
     const TargetRegisterInfo &TRI) const {
@@ -441,13 +454,13 @@ void RegisterBankInfo::applyDefaultMapping(const OperandsMapper &OpdMapper) {
 
 unsigned RegisterBankInfo::getSizeInBits(unsigned Reg,
                                          const MachineRegisterInfo &MRI,
-                                         const TargetRegisterInfo &TRI) {
+                                         const TargetRegisterInfo &TRI) const {
   const TargetRegisterClass *RC = nullptr;
   if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
     // The size is not directly available for physical registers.
     // Instead, we need to access a register class that contains Reg and
     // get the size of that register class.
-    RC = TRI.getMinimalPhysRegClass(Reg);
+    RC = &getMinimalPhysRegClass(Reg, TRI);
   } else {
     LLT Ty = MRI.getType(Reg);
     unsigned RegSize = Ty.isValid() ? Ty.getSizeInBits() : 0;
@@ -546,7 +559,8 @@ bool RegisterBankInfo::InstructionMapping::verify(
   assert(MI.getParent() && MI.getMF() &&
          "MI must be connected to a MachineFunction");
   const MachineFunction &MF = *MI.getMF();
-  (void)MF;
+  const RegisterBankInfo *RBI = MF.getSubtarget().getRegBankInfo();
+  (void)RBI;
 
   for (unsigned Idx = 0; Idx < NumOperands; ++Idx) {
     const MachineOperand &MO = MI.getOperand(Idx);
@@ -564,7 +578,7 @@ bool RegisterBankInfo::InstructionMapping::verify(
     (void)MOMapping;
     // Register size in bits.
     // This size must match what the mapping expects.
-    assert(MOMapping.verify(getSizeInBits(
+    assert(MOMapping.verify(RBI->getSizeInBits(
                Reg, MF.getRegInfo(), *MF.getSubtarget().getRegisterInfo())) &&
            "Value mapping is invalid");
   }