//===-- RegAllocSimple.cpp - A simple generic register allocator ----------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
//
// This file implements a simple register allocator. *Very* simple: It immediate
// spills every value right after it is computed, and it reloads all used
//
//===----------------------------------------------------------------------===//
+#define DEBUG_TYPE "regalloc"
+#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/SSARegMap.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
-#include "llvm/Target/MachineInstrInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetMachine.h"
+#include "Support/Debug.h"
#include "Support/Statistic.h"
#include <iostream>
/// runOnMachineFunction - Register allocate the whole function
bool runOnMachineFunction(MachineFunction &Fn);
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequiredID(PHIEliminationID); // Eliminate PHI nodes
+ MachineFunctionPass::getAnalysisUsage(AU);
+ }
private:
/// AllocateBasicBlock - Register allocate the specified basic block.
void AllocateBasicBlock(MachineBasicBlock &MBB);
- /// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions
- /// in predecessor basic blocks.
- void EliminatePHINodes(MachineBasicBlock &MBB);
-
/// getStackSpaceFor - This returns the offset of the specified virtual
- /// register on the stack, allocating space if neccesary.
+ /// register on the stack, allocating space if necessary.
int getStackSpaceFor(unsigned VirtReg, const TargetRegisterClass *RC);
/// Given a virtual register, return a compatible physical register that is
return I->second; // Already has space allocated?
// Allocate a new stack object for this spill location...
- int FrameIdx =
- MF->getFrameInfo()->CreateStackObject(RC->getSize(), RC->getAlignment());
+ int FrameIdx = MF->getFrameInfo()->CreateStackObject(RC);
// Assign the slot...
StackSlotForVirtReg.insert(I, std::make_pair(VirtReg, FrameIdx));
}
-/// EliminatePHINodes - Eliminate phi nodes by inserting copy instructions in
-/// predecessor basic blocks.
-///
-void RegAllocSimple::EliminatePHINodes(MachineBasicBlock &MBB) {
- const MachineInstrInfo &MII = TM->getInstrInfo();
-
- while (MBB.front()->getOpcode() == MachineInstrInfo::PHI) {
- MachineInstr *MI = MBB.front();
- // Unlink the PHI node from the basic block... but don't delete the PHI yet
- MBB.erase(MBB.begin());
-
- DEBUG(std::cerr << "num ops: " << MI->getNumOperands() << "\n");
- assert(MI->getOperand(0).isVirtualRegister() &&
- "PHI node doesn't write virt reg?");
-
- unsigned virtualReg = MI->getOperand(0).getAllocatedRegNum();
-
- for (int i = MI->getNumOperands() - 1; i >= 2; i-=2) {
- MachineOperand &opVal = MI->getOperand(i-1);
-
- // Get the MachineBasicBlock equivalent of the BasicBlock that is the
- // source path the phi
- MachineBasicBlock &opBlock = *MI->getOperand(i).getMachineBasicBlock();
-
- // Check to make sure we haven't already emitted the copy for this block.
- // This can happen because PHI nodes may have multiple entries for the
- // same basic block. It doesn't matter which entry we use though, because
- // all incoming values are guaranteed to be the same for a particular bb.
- //
- // Note that this is N^2 in the number of phi node entries, but since the
- // # of entries is tiny, this is not a problem.
- //
- bool HaveNotEmitted = true;
- for (int op = MI->getNumOperands() - 1; op != i; op -= 2)
- if (&opBlock == MI->getOperand(op).getMachineBasicBlock()) {
- HaveNotEmitted = false;
- break;
- }
-
- if (HaveNotEmitted) {
- MachineBasicBlock::iterator opI = opBlock.end();
- MachineInstr *opMI = *--opI;
-
- // must backtrack over ALL the branches in the previous block
- while (MII.isBranch(opMI->getOpcode()) && opI != opBlock.begin())
- opMI = *--opI;
-
- // move back to the first branch instruction so new instructions
- // are inserted right in front of it and not in front of a non-branch
- //
- if (!MII.isBranch(opMI->getOpcode()))
- ++opI;
-
- const TargetRegisterClass *RC =
- MF->getSSARegMap()->getRegClass(virtualReg);
-
- assert(opVal.isVirtualRegister() &&
- "Machine PHI Operands must all be virtual registers!");
- RegInfo->copyRegToReg(opBlock, opI, virtualReg, opVal.getReg(), RC);
- }
- }
-
- // really delete the PHI instruction now!
- delete MI;
- }
-}
-
-
void RegAllocSimple::AllocateBasicBlock(MachineBasicBlock &MBB) {
// loop over each instruction
for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I) {
// a preliminary pass that will invalidate any registers that
// are used by the instruction (including implicit uses)
unsigned Opcode = MI->getOpcode();
- const MachineInstrDescriptor &Desc = TM->getInstrInfo().get(Opcode);
- if (const unsigned *Regs = Desc.ImplicitUses)
- while (*Regs)
- RegsUsed[*Regs++] = true;
+ const TargetInstrDescriptor &Desc = TM->getInstrInfo().get(Opcode);
+ const unsigned *Regs = Desc.ImplicitUses;
+ while (*Regs)
+ RegsUsed[*Regs++] = true;
- if (const unsigned *Regs = Desc.ImplicitDefs)
- while (*Regs)
- RegsUsed[*Regs++] = true;
+ Regs = Desc.ImplicitDefs;
+ while (*Regs)
+ RegsUsed[*Regs++] = true;
// Loop over uses, move from memory into registers
for (int i = MI->getNumOperands() - 1; i >= 0; --i) {
// register in any given instruction
unsigned physReg = Virt2PhysRegMap[virtualReg];
if (physReg == 0) {
- if (op.opIsDef()) {
+ if (op.opIsDefOnly() || op.opIsDefAndUse()) {
if (TM->getInstrInfo().isTwoAddrInstr(MI->getOpcode()) && i == 0) {
// must be same register number as the first operand
// This maps a = b + c into b += c, and saves b into a's spot
TM = &MF->getTarget();
RegInfo = TM->getRegisterInfo();
- // First pass: eliminate PHI instructions by inserting copies into predecessor
- // blocks.
- for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
- MBB != MBBe; ++MBB)
- EliminatePHINodes(*MBB);
-
// Loop over all of the basic blocks, eliminating virtual register references
for (MachineFunction::iterator MBB = Fn.begin(), MBBe = Fn.end();
MBB != MBBe; ++MBB)
return true;
}
-Pass *createSimpleRegisterAllocator() {
+FunctionPass *createSimpleRegisterAllocator() {
return new RegAllocSimple();
}