2002-10-28 01:41:47 +00:00
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//===-- PeepholeOpts.cpp --------------------------------------------------===//
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2002-09-20 00:42:11 +00:00
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//
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2002-10-28 01:41:47 +00:00
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// Support for performing several peephole opts in one or a few passes over the
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// machine code of a method.
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//
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//===----------------------------------------------------------------------===//
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2002-09-20 00:42:11 +00:00
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2003-09-01 20:33:07 +00:00
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#include "SparcInternals.h"
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2002-10-28 20:00:31 +00:00
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#include "llvm/CodeGen/MachineFunction.h"
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2002-09-20 00:42:11 +00:00
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/Target/TargetMachine.h"
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2003-01-14 22:00:31 +00:00
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#include "llvm/Target/TargetInstrInfo.h"
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2002-09-20 00:42:11 +00:00
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#include "llvm/BasicBlock.h"
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#include "llvm/Pass.h"
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//************************* Internal Functions *****************************/
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2003-09-01 20:24:06 +00:00
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static inline void
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2002-10-28 01:41:47 +00:00
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DeleteInstruction(MachineBasicBlock& mvec,
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MachineBasicBlock::iterator& BBI,
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const TargetMachine& target) {
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// Check if this instruction is in a delay slot of its predecessor.
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if (BBI != mvec.begin()) {
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const TargetInstrInfo& mii = target.getInstrInfo();
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MachineInstr* predMI = *(BBI-1);
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if (unsigned ndelay = mii.getNumDelaySlots(predMI->getOpCode())) {
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// This instruction is in a delay slot of its predecessor, so
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// replace it with a nop. By replacing in place, we save having
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// to update the I-I maps.
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//
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assert(ndelay == 1 && "Not yet handling multiple-delay-slot targets");
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(*BBI)->replace(mii.getNOPOpCode(), 0);
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return;
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}
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}
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2002-09-27 14:27:37 +00:00
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// The instruction is not in a delay slot, so we can simply erase it.
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mvec.erase(BBI);
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BBI = mvec.end();
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2002-09-20 00:42:11 +00:00
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}
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//******************* Individual Peephole Optimizations ********************/
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2003-09-01 20:38:03 +00:00
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//----------------------------------------------------------------------------
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// Function: IsUselessCopy
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// Decide whether a machine instruction is a redundant copy:
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// -- ADD with g0 and result and operand are identical, or
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// -- OR with g0 and result and operand are identical, or
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// -- FMOVS or FMOVD and result and operand are identical.
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// Other cases are possible but very rare that they would be useless copies,
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// so it's not worth analyzing them.
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//----------------------------------------------------------------------------
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static bool IsUselessCopy(const TargetMachine &target, const MachineInstr* MI) {
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if (MI->getOpCode() == V9::FMOVS || MI->getOpCode() == V9::FMOVD) {
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return (/* both operands are allocated to the same register */
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MI->getOperand(0).getAllocatedRegNum() ==
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MI->getOperand(1).getAllocatedRegNum());
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} else if (MI->getOpCode() == V9::ADDr || MI->getOpCode() == V9::ORr) {
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unsigned srcWithDestReg;
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for (srcWithDestReg = 0; srcWithDestReg < 2; ++srcWithDestReg)
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if (MI->getOperand(srcWithDestReg).hasAllocatedReg() &&
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MI->getOperand(srcWithDestReg).getAllocatedRegNum()
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== MI->getOperand(2).getAllocatedRegNum())
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break;
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if (srcWithDestReg == 2)
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return false;
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else {
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/* else source and dest are allocated to the same register */
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unsigned otherOp = 1 - srcWithDestReg;
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return (/* either operand otherOp is register %g0 */
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(MI->getOperand(otherOp).hasAllocatedReg() &&
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MI->getOperand(otherOp).getAllocatedRegNum() ==
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target.getRegInfo().getZeroRegNum()) ||
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/* or operand otherOp == 0 */
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(MI->getOperand(otherOp).getType()
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== MachineOperand::MO_SignExtendedImmed &&
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MI->getOperand(otherOp).getImmedValue() == 0));
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}
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}
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else
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return false;
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}
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2002-09-20 00:42:11 +00:00
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inline bool
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RemoveUselessCopies(MachineBasicBlock& mvec,
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MachineBasicBlock::iterator& BBI,
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const TargetMachine& target) {
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if (IsUselessCopy(target, *BBI)) {
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DeleteInstruction(mvec, BBI, target);
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return true;
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}
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return false;
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}
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//************************ Class Implementations **************************/
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class PeepholeOpts: public BasicBlockPass {
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const TargetMachine ⌖
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bool visit(MachineBasicBlock& mvec,
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MachineBasicBlock::iterator BBI) const;
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public:
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PeepholeOpts(const TargetMachine &T): target(T) { }
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bool runOnBasicBlock(BasicBlock &BB); // apply this pass to each BB
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virtual const char *getPassName() const { return "Peephole Optimization"; }
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};
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2003-09-01 20:24:06 +00:00
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// Apply a list of peephole optimizations to this machine instruction
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// within its local context. They are allowed to delete MI or any
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// instruction before MI, but not
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//
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bool PeepholeOpts::visit(MachineBasicBlock& mvec,
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MachineBasicBlock::iterator BBI) const {
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/* Remove redundant copy instructions */
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return RemoveUselessCopies(mvec, BBI, target);
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}
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bool PeepholeOpts::runOnBasicBlock(BasicBlock &BB) {
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// Get the machine instructions for this BB
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// FIXME: MachineBasicBlock::get() is deprecated, hence inlining the function
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const Function *F = BB.getParent();
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MachineFunction &MF = MachineFunction::get(F);
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MachineBasicBlock *MBB = NULL;
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for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
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if (I->getBasicBlock() == &BB)
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MBB = I;
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assert(MBB && "MachineBasicBlock object not found for specified block!");
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MachineBasicBlock &mvec = *MBB;
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// Iterate over all machine instructions in the BB
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// Use a reverse iterator to allow deletion of MI or any instruction after it.
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// Insertions or deletions *before* MI are not safe.
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//
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for (MachineBasicBlock::reverse_iterator RI=mvec.rbegin(),
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RE=mvec.rend(); RI != RE; ) {
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MachineBasicBlock::iterator BBI = RI.base()-1; // save before incr
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++RI; // pre-increment to delete MI or after it
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visit(mvec, BBI);
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}
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return true;
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}
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//===----------------------------------------------------------------------===//
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// createPeepholeOptsPass - Public entrypoint for peephole optimization
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// and this file as a whole...
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//
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FunctionPass* createPeepholeOptsPass(TargetMachine &T) {
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return new PeepholeOpts(T);
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}
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