Mark 64-bit register RA_64 unused too.

[oota-llvm.git] / lib / Target / Mips / MipsDelaySlotFiller.cpp

diff --git a/lib/Target/Mips/MipsDelaySlotFiller.cpp b/lib/Target/Mips/MipsDelaySlotFiller.cpp
index 690f4ffb3854ca2699e84efef65cd48320ea50da..05cee65f9fa611aeb6dbfcf0358512dd1c8d3721 100644 (file)
--- a/lib/Target/Mips/MipsDelaySlotFiller.cpp
+++ b/lib/Target/Mips/MipsDelaySlotFiller.cpp
@@ -28,7 +28,7 @@ using namespace llvm;
 
 STATISTIC(FilledSlots, "Number of delay slots filled");
 STATISTIC(UsefulSlots, "Number of delay slots filled with instructions that"
-                       "are not NOP.");
+                       " are not NOP.");
 
 static cl::opt<bool> EnableDelaySlotFiller(
   "enable-mips-delay-filler",
@@ -96,7 +96,7 @@ runOnMachineBasicBlock(MachineBasicBlock &MBB) {
   LastFiller = MBB.end();
 
   for (MachineBasicBlock::iterator I = MBB.begin(); I != MBB.end(); ++I)
-    if (I->getDesc().hasDelaySlot()) {
+    if (I->hasDelaySlot()) {
       ++FilledSlots;
       Changed = true;
 
@@ -105,8 +105,7 @@ runOnMachineBasicBlock(MachineBasicBlock &MBB) {
       if (EnableDelaySlotFiller && findDelayInstr(MBB, I, D)) {
         MBB.splice(llvm::next(I), &MBB, D);
         ++UsefulSlots;
-      }
-      else 
+      } else 
         BuildMI(MBB, llvm::next(I), I->getDebugLoc(), TII->get(Mips::NOP));
 
       // Record the filler instruction that filled the delay slot.
@@ -128,34 +127,25 @@ bool Filler::findDelayInstr(MachineBasicBlock &MBB,
                             MachineBasicBlock::iterator &Filler) {
   SmallSet<unsigned, 32> RegDefs;
   SmallSet<unsigned, 32> RegUses;
-  bool sawLoad = false;
-  bool sawStore = false;
-
-  MachineBasicBlock::iterator I = slot;
-
-  // Call's delay filler can def some of call's uses.
-  if (slot->getDesc().isCall())
-    insertCallUses(slot, RegDefs, RegUses);
-  else
-    insertDefsUses(slot, RegDefs, RegUses);
-
-  bool done = false;
 
-  while (!done) {
-    done = (I == MBB.begin());
+  insertDefsUses(slot, RegDefs, RegUses);
 
-    if (!done)
-      --I;
+  bool sawLoad = false;
+  bool sawStore = false;
 
+  for (MachineBasicBlock::reverse_iterator I(slot); I != MBB.rend(); ++I) {
     // skip debug value
     if (I->isDebugValue())
       continue;
 
+    // Convert to forward iterator.
+    MachineBasicBlock::iterator FI(llvm::next(I).base());
+
     if (I->hasUnmodeledSideEffects()
         || I->isInlineAsm()
         || I->isLabel()
-        || I == LastFiller
-        || I->getDesc().isPseudo()
+        || FI == LastFiller
+        || I->isPseudo()
         //
         // Should not allow:
         // ERET, DERET or WAIT, PAUSE. Need to add these to instruction
@@ -163,12 +153,12 @@ bool Filler::findDelayInstr(MachineBasicBlock &MBB,
         )
       break;
 
-    if (delayHasHazard(I, sawLoad, sawStore, RegDefs, RegUses)) {
-      insertDefsUses(I, RegDefs, RegUses);
+    if (delayHasHazard(FI, sawLoad, sawStore, RegDefs, RegUses)) {
+      insertDefsUses(FI, RegDefs, RegUses);
       continue;
     }
 
-    Filler = I;
+    Filler = FI;
     return true;
   }
 
@@ -176,8 +166,7 @@ bool Filler::findDelayInstr(MachineBasicBlock &MBB,
 }
 
 bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
-                            bool &sawLoad,
-                            bool &sawStore,
+                            bool &sawLoad, bool &sawStore,
                             SmallSet<unsigned, 32> &RegDefs,
                             SmallSet<unsigned, 32> &RegUses) {
   if (candidate->isImplicitDef() || candidate->isKill())
@@ -185,13 +174,13 @@ bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
 
   // Loads or stores cannot be moved past a store to the delay slot
   // and stores cannot be moved past a load. 
-  if (candidate->getDesc().mayLoad()) {
+  if (candidate->mayLoad()) {
     if (sawStore)
       return true;
     sawLoad = true;
   }
 
-  if (candidate->getDesc().mayStore()) {
+  if (candidate->mayStore()) {
     if (sawStore)
       return true;
     sawStore = true;
@@ -199,12 +188,15 @@ bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
       return true;
   }
 
+  assert((!candidate->isCall() && !candidate->isReturn()) &&
+         "Cannot put calls or returns in delay slot.");
+
   for (unsigned i = 0, e = candidate->getNumOperands(); i!= e; ++i) {
     const MachineOperand &MO = candidate->getOperand(i);
-    if (!MO.isReg())
-      continue; // skip
+    unsigned Reg;
 
-    unsigned Reg = MO.getReg();
+    if (!MO.isReg() || !(Reg = MO.getReg()))
+      continue; // skip
 
     if (MO.isDef()) {
       // check whether Reg is defined or used before delay slot.
@@ -220,39 +212,29 @@ bool Filler::delayHasHazard(MachineBasicBlock::iterator candidate,
   return false;
 }
 
-void Filler::insertCallUses(MachineBasicBlock::iterator MI,
-                            SmallSet<unsigned, 32>& RegDefs,
-                            SmallSet<unsigned, 32>& RegUses) {
-  switch(MI->getOpcode()) {
-  default: llvm_unreachable("Unknown opcode.");
-  case Mips::JAL:
-    RegDefs.insert(31);
-    break;
-  case Mips::JALR:
-    assert(MI->getNumOperands() >= 1);
-    const MachineOperand &Reg = MI->getOperand(0);
-    assert(Reg.isReg() && "JALR first operand is not a register.");
-    RegUses.insert(Reg.getReg());
-    RegDefs.insert(31);
-    break;
-  }
-}
-
 // Insert Defs and Uses of MI into the sets RegDefs and RegUses.
 void Filler::insertDefsUses(MachineBasicBlock::iterator MI,
                             SmallSet<unsigned, 32>& RegDefs,
                             SmallSet<unsigned, 32>& RegUses) {
-  for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+  // If MI is a call or return, just examine the explicit non-variadic operands.
+  MCInstrDesc MCID = MI->getDesc();
+  unsigned e = MI->isCall() || MI->isReturn() ? MCID.getNumOperands() :
+                                                MI->getNumOperands();
+  
+  // Add RA to RegDefs to prevent users of RA from going into delay slot. 
+  if (MI->isCall())
+    RegDefs.insert(Mips::RA);
+
+  for (unsigned i = 0; i != e; ++i) {
     const MachineOperand &MO = MI->getOperand(i);
-    if (!MO.isReg())
-      continue;
+    unsigned Reg;
 
-    unsigned Reg = MO.getReg();
-    if (Reg == 0)
+    if (!MO.isReg() || !(Reg = MO.getReg()))
       continue;
+
     if (MO.isDef())
       RegDefs.insert(Reg);
-    if (MO.isUse())
+    else if (MO.isUse())
       RegUses.insert(Reg);
   }
 }