Move machine code rewriter and spiller outside the register

allocator.

The implementation is completely rewritten and now employs several
optimizations not exercised before. For example for 164.gzip we have
997 loads and 699 stores vs the 1221 loads and 880 stores we have
before.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@11798 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/VirtRegMap.cpp

@@ -7,20 +7,32 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// This file implements the virtual register map.
+// This file implements the virtual register map. It also implements
+// the eliminateVirtRegs() function that given a virtual register map
+// and a machine function it eliminates all virtual references by
+// replacing them with physical register references and adds spill
+// code as necessary.
 //
 //===----------------------------------------------------------------------===//
 
+#define DEBUG_TYPE "regalloc"
 #include "VirtRegMap.h"
+#include "llvm/Function.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/Target/TargetMachine.h"
+#include "llvm/Target/TargetInstrInfo.h"
 #include "Support/Statistic.h"
+#include "Support/Debug.h"
+#include "Support/STLExtras.h"
 #include <iostream>
 
 using namespace llvm;
 
 namespace {
-    Statistic<> numSpills("ra-linearscan", "Number of register spills");
+    Statistic<> numSpills("spiller", "Number of register spills");
+    Statistic<> numStores("spiller", "Number of stores added");
+    Statistic<> numLoads ("spiller", "Number of loads added");
+
 }
 
 int VirtRegMap::assignVirt2StackSlot(unsigned virtReg)
@@ -53,3 +65,148 @@ std::ostream& llvm::operator<<(std::ostream& os, const VirtRegMap& vrm)
     }
     return std::cerr << '\n';
 }
+
+namespace {
+
+    class Spiller {
+        typedef std::vector<unsigned> Phys2VirtMap;
+        typedef std::vector<bool> PhysFlag;
+
+        MachineFunction& mf_;
+        const TargetMachine& tm_;
+        const TargetInstrInfo& tii_;
+        const MRegisterInfo& mri_;
+        const VirtRegMap& vrm_;
+        Phys2VirtMap p2vMap_;
+        PhysFlag dirty_;
+
+    public:
+        Spiller(MachineFunction& mf, const VirtRegMap& vrm)
+            : mf_(mf),
+              tm_(mf_.getTarget()),
+              tii_(tm_.getInstrInfo()),
+              mri_(*tm_.getRegisterInfo()),
+              vrm_(vrm),
+              p2vMap_(mri_.getNumRegs()),
+              dirty_(mri_.getNumRegs()) {
+            DEBUG(std::cerr << "********** REWRITE MACHINE CODE **********\n");
+            DEBUG(std::cerr << "********** Function: "
+                  << mf_.getFunction()->getName() << '\n');
+        }
+
+        void eliminateVirtRegs() {
+            for (MachineFunction::iterator mbbi = mf_.begin(),
+                     mbbe = mf_.end(); mbbi != mbbe; ++mbbi) {
+                // clear map and dirty flag
+                p2vMap_.assign(p2vMap_.size(), 0);
+                dirty_.assign(dirty_.size(), false);
+                DEBUG(std::cerr << mbbi->getBasicBlock()->getName() << ":\n");
+                eliminateVirtRegsInMbb(*mbbi);
+            }
+        }
+
+    private:
+        void vacateJustPhysReg(MachineBasicBlock& mbb,
+                               MachineBasicBlock::iterator mii,
+                               unsigned physReg) {
+            unsigned virtReg = p2vMap_[physReg];
+            if (dirty_[physReg] && vrm_.hasStackSlot(virtReg)) {
+                mri_.storeRegToStackSlot(mbb, mii, physReg,
+                                         vrm_.getStackSlot(virtReg),
+                                         mri_.getRegClass(physReg));
+                ++numStores;
+                DEBUG(std::cerr << "*\t"; prior(mii)->print(std::cerr, tm_));
+            }
+            p2vMap_[physReg] = 0;
+            dirty_[physReg] = false;
+        }
+
+        void vacatePhysReg(MachineBasicBlock& mbb,
+                           MachineBasicBlock::iterator mii,
+                           unsigned physReg) {
+            vacateJustPhysReg(mbb, mii, physReg);
+            for (const unsigned* as = mri_.getAliasSet(physReg); *as; ++as)
+                vacateJustPhysReg(mbb, mii, *as);
+        }
+
+        void handleUse(MachineBasicBlock& mbb,
+                       MachineBasicBlock::iterator mii,
+                       unsigned virtReg,
+                       unsigned physReg) {
+            // check if we are replacing a previous mapping
+            if (p2vMap_[physReg] != virtReg) {
+                vacatePhysReg(mbb, mii, physReg);
+                p2vMap_[physReg] = virtReg;
+                // load if necessary
+                if (vrm_.hasStackSlot(virtReg)) {
+                    mri_.loadRegFromStackSlot(mbb, mii, physReg,
+                                              vrm_.getStackSlot(virtReg),
+                                              mri_.getRegClass(physReg));
+                    ++numLoads;
+                    DEBUG(std::cerr << "*\t"; prior(mii)->print(std::cerr,tm_));
+                }
+            }
+        }
+
+        void handleDef(MachineBasicBlock& mbb,
+                       MachineBasicBlock::iterator mii,
+                       unsigned virtReg,
+                       unsigned physReg) {
+            // check if we are replacing a previous mapping
+            if (p2vMap_[physReg] != virtReg)
+                vacatePhysReg(mbb, mii, physReg);
+
+            p2vMap_[physReg] = virtReg;
+            dirty_[physReg] = true;
+        }
+
+        void eliminateVirtRegsInMbb(MachineBasicBlock& mbb) {
+            for (MachineBasicBlock::iterator mii = mbb.begin(),
+                     mie = mbb.end(); mii != mie; ++mii) {
+                // rewrite all used operands
+                for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
+                    MachineOperand& op = mii->getOperand(i);
+                    if (op.isRegister() && op.isUse() &&
+                        MRegisterInfo::isVirtualRegister(op.getReg())) {
+                        unsigned physReg = vrm_.getPhys(op.getReg());
+                        handleUse(mbb, mii, op.getReg(), physReg);
+                        mii->SetMachineOperandReg(i, physReg);
+                        // mark as dirty if this is def&use
+                        if (op.isDef()) dirty_[physReg] = true;
+                    }
+                }
+
+                // spill implicit defs
+                const TargetInstrDescriptor& tid =tii_.get(mii->getOpcode());
+                for (const unsigned* id = tid.ImplicitDefs; *id; ++id)
+                    vacatePhysReg(mbb, mii, *id);
+
+                // rewrite def operands (def&use was handled with the
+                // uses so don't check for those here)
+                for (unsigned i = 0, e = mii->getNumOperands(); i != e; ++i) {
+                    MachineOperand& op = mii->getOperand(i);
+                    if (op.isRegister() && !op.isUse())
+                        if (MRegisterInfo::isPhysicalRegister(op.getReg()))
+                            vacatePhysReg(mbb, mii, op.getReg());
+                        else {
+                            unsigned physReg = vrm_.getPhys(op.getReg());
+                            handleDef(mbb, mii, op.getReg(), physReg);
+                            mii->SetMachineOperandReg(i, physReg);
+                        }
+                }
+
+                DEBUG(std::cerr << '\t'; mii->print(std::cerr, tm_));
+            }
+
+            for (unsigned i = 1, e = p2vMap_.size(); i != e; ++i)
+                vacateJustPhysReg(mbb, mbb.getFirstTerminator(), i);
+
+        }
+    };
+}
+
+
+void llvm::eliminateVirtRegs(MachineFunction& mf, const VirtRegMap& vrm)
+{
+    Spiller(mf, vrm).eliminateVirtRegs();
+}