Add a "nop filler" pass to SPU.

Filling no-ops is done just before emitting of assembly,
when the instruction stream is final. No-ops are inserted
to align the instructions so the dual-issue of the pipeline
is utilized. This speeds up generated code with a minimum of 
1% on a select set of algorithms.

This pass may be redundant if the instruction scheduler and 
all subsequent passes that modify the instruction stream 
(prolog+epilog inserter, register scavenger, are there others?)
are made aware of the instruction alignments.

llvm-svn: 123226

lib/Target/CellSPU/CMakeLists.txt

@@ -23,4 +23,5 @@ add_llvm_target(CellSPUCodeGen
   SPUSubtarget.cpp
   SPUTargetMachine.cpp
   SPUSelectionDAGInfo.cpp
+  SPUNopFiller.cpp
   )

lib/Target/CellSPU/SPU.h

@@ -23,6 +23,7 @@ namespace llvm {
   class formatted_raw_ostream;
 
   FunctionPass *createSPUISelDag(SPUTargetMachine &TM);
+  FunctionPass *createSPUNopFillerPass(SPUTargetMachine &tm);
 
   extern Target TheCellSPUTarget;
 }

lib/Target/CellSPU/SPUInstrInfo.td

@@ -4216,7 +4216,7 @@ def : Pat<(fabs (v4f32 VECREG:$rA)),
 // in the odd pipeline)
 //===----------------------------------------------------------------------===//
 
-def ENOP : SPUInstr<(outs), (ins), "enop", ExecNOP> {
+def ENOP : SPUInstr<(outs), (ins), "nop", ExecNOP> {
   let Pattern = [];
 
   let Inst{0-10} = 0b10000000010;

lib/Target/CellSPU/SPUNopFiller.cpp

@@ -0,0 +1,153 @@
+//===-- SPUNopFiller.cpp - Add nops/lnops to align the pipelines---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// The final pass just before assembly printing. This pass is the last
+// checkpoint where nops and lnops are added to the instruction stream to 
+// satisfy the dual issue requirements. The actual dual issue scheduling is 
+// done (TODO: nowhere, currently)
+//
+//===----------------------------------------------------------------------===//
+
+#include "SPU.h"
+#include "SPUTargetMachine.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace llvm;
+
+namespace {
+  struct SPUNopFiller : public MachineFunctionPass {
+
+    TargetMachine &TM;
+    const TargetInstrInfo *TII;
+    const InstrItineraryData *IID;
+    bool isEvenPlace;  // the instruction slot (mem address) at hand is even/odd
+
+    static char ID;
+    SPUNopFiller(TargetMachine &tm) 
+      : MachineFunctionPass(ID), TM(tm), TII(tm.getInstrInfo()), 
+        IID(tm.getInstrItineraryData()) 
+    {
+      DEBUG( dbgs() << "********** SPU Nop filler **********\n" ; );
+    }
+
+    virtual const char *getPassName() const {
+      return "SPU nop/lnop Filler";
+    }
+
+    void runOnMachineBasicBlock(MachineBasicBlock &MBB);
+
+    bool runOnMachineFunction(MachineFunction &F) {
+      isEvenPlace = true; //all functions get an .align 3 directive at start 
+      for (MachineFunction::iterator FI = F.begin(), FE = F.end();
+           FI != FE; ++FI)
+        runOnMachineBasicBlock(*FI);
+      return true; //never-ever do any more modifications, just print it!
+    }
+
+    typedef enum { none   = 0, // no more instructions in this function / BB
+                   pseudo = 1, // this does not get executed
+                   even   = 2, 
+                   odd    = 3 } SPUOpPlace;
+    SPUOpPlace getOpPlacement( MachineInstr &instr );
+
+  };
+  char SPUNopFiller::ID = 0;
+
+} 
+
+// Fill a BasicBlock to alignment. 
+// In the assebly we align the functions to 'even' adresses, but
+// basic blocks have an implicit alignmnet. We hereby define 
+// basic blocks to have the same, even, alignment.
+void SPUNopFiller::
+runOnMachineBasicBlock(MachineBasicBlock &MBB) 
+{
+  assert( isEvenPlace && "basic block start from odd address");
+  for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
+  {
+    SPUOpPlace this_optype, next_optype;
+    MachineBasicBlock::iterator J = I;
+    J++;
+
+    this_optype = getOpPlacement( *I );
+    next_optype = none;
+    while (J!=MBB.end()){
+      next_optype = getOpPlacement( *J );
+      ++J;
+      if (next_optype != pseudo ) 
+        break;
+    }
+
+    // padd: odd(wrong), even(wrong), ...
+    // to:   nop(corr), odd(corr), even(corr)...
+    if( isEvenPlace && this_optype == odd && next_optype == even ) {
+      DEBUG( dbgs() <<"Adding NOP before: "; );
+      DEBUG( I->dump(); );
+      BuildMI(MBB, I, I->getDebugLoc(), TII->get(SPU::ENOP));
+      isEvenPlace=false;
+    }
+    
+    // padd: even(wrong), odd(wrong), ...
+    // to:   lnop(corr), even(corr), odd(corr)...
+    else if ( !isEvenPlace && this_optype == even && next_optype == odd){
+      DEBUG( dbgs() <<"Adding LNOP before: "; );
+      DEBUG( I->dump(); );
+      BuildMI(MBB, I, I->getDebugLoc(), TII->get(SPU::LNOP));
+      isEvenPlace=true;
+    }
+      
+    // now go to next mem slot
+    if( this_optype != pseudo )
+      isEvenPlace = !isEvenPlace;    
+
+  }
+
+  // padd basicblock end
+  if( !isEvenPlace ){
+    MachineBasicBlock::iterator J = MBB.end();
+    J--;
+    if (getOpPlacement( *J ) == odd) {
+      DEBUG( dbgs() <<"Padding basic block with NOP\n"; );
+      BuildMI(MBB, J, J->getDebugLoc(), TII->get(SPU::ENOP));
+    }  
+    else {
+      J++;
+      DEBUG( dbgs() <<"Padding basic block with LNOP\n"; );
+      BuildMI(MBB, J, J->getDebugLoc(), TII->get(SPU::LNOP));
+    }
+    isEvenPlace=true;
+  }
+}
+
+FunctionPass *llvm::createSPUNopFillerPass(SPUTargetMachine &tm) {
+  return new SPUNopFiller(tm);
+}
+
+// Figure out if 'instr' is executed in the even or odd pipeline
+SPUNopFiller::SPUOpPlace 
+SPUNopFiller::getOpPlacement( MachineInstr &instr ) {
+  int sc = instr.getDesc().getSchedClass();
+  const InstrStage *stage = IID->beginStage(sc);
+  unsigned FUs = stage->getUnits();
+  SPUOpPlace retval;
+
+  switch( FUs ) {
+    case 0: retval = pseudo; break;
+    case 1: retval = odd;    break;
+    case 2: retval = even;   break;
+    default: retval= pseudo; 
+             assert( false && "got unknown FuncUnit\n");
+             break;
+  };
+  return retval;
+}

lib/Target/CellSPU/SPUTargetMachine.cpp

@@ -59,3 +59,12 @@ bool SPUTargetMachine::addInstSelector(PassManagerBase &PM,
   PM.add(createSPUISelDag(*this));
   return false;
 }
+
+// passes to run just before printing the assembly
+bool SPUTargetMachine::
+addPreEmitPass(PassManagerBase &PM, CodeGenOpt::Level OptLevel) 
+{
+  //align instructions with nops/lnops for dual issue
+  PM.add(createSPUNopFillerPass(*this));
+  return true;
+}

lib/Target/CellSPU/SPUTargetMachine.h

@@ -82,6 +82,7 @@ public:
   // Pass Pipeline Configuration
   virtual bool addInstSelector(PassManagerBase &PM,
                                CodeGenOpt::Level OptLevel);
+  virtual bool addPreEmitPass(PassManagerBase &, CodeGenOpt::Level);	
 };
 
 } // end namespace llvm