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https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@6312 91177308-0d34-0410-b5e6-96231b3b80d8
136 lines
4.1 KiB
C++
136 lines
4.1 KiB
C++
//===-- PeepholeOpts.cpp --------------------------------------------------===//
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//
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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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#include "llvm/CodeGen/PeepholeOpts.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetOptInfo.h"
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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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inline void
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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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{
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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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// 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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}
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//******************* Individual Peephole Optimizations ********************/
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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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{
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if (target.getOptInfo().IsUselessCopy(*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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};
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// Register the pass with llc only, and not opt...
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static RegisterLLC<PeepholeOpts>
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X("peephole", "Peephole Optimization", createPeepholeOptsPass);
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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
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PeepholeOpts::visit(MachineBasicBlock& mvec,
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MachineBasicBlock::iterator BBI) const
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{
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bool changed = false;
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/* Remove redundant copy instructions */
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changed |= RemoveUselessCopies(mvec, BBI, target);
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if (BBI == mvec.end()) // nothing more to do!
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return changed;
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return changed;
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}
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bool
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PeepholeOpts::runOnBasicBlock(BasicBlock &BB)
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{
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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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}
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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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{
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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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Pass*
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createPeepholeOptsPass(TargetMachine &T)
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{
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return new PeepholeOpts(T);
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}
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