Constrain register classes instead of emitting copies.

[oota-llvm.git] / lib / CodeGen / DeadMachineInstructionElim.cpp

diff --git a/lib/CodeGen/DeadMachineInstructionElim.cpp b/lib/CodeGen/DeadMachineInstructionElim.cpp
index b4f784d87e7be94da921862f2b7a9e1294e72405..6de6c0cb81bdd906a8621c326ed352e4dfa389da 100644 (file)
--- a/lib/CodeGen/DeadMachineInstructionElim.cpp
+++ b/lib/CodeGen/DeadMachineInstructionElim.cpp
@@ -36,7 +36,9 @@ namespace {
 
   public:
     static char ID; // Pass identification, replacement for typeid
-    DeadMachineInstructionElim() : MachineFunctionPass(ID) {}
+    DeadMachineInstructionElim() : MachineFunctionPass(ID) {
+     initializeDeadMachineInstructionElimPass(*PassRegistry::getPassRegistry());
+    }
 
   private:
     bool isDead(const MachineInstr *MI) const;
@@ -52,6 +54,12 @@ FunctionPass *llvm::createDeadMachineInstructionElimPass() {
 }
 
 bool DeadMachineInstructionElim::isDead(const MachineInstr *MI) const {
+  // Technically speaking inline asm without side effects and no defs can still
+  // be deleted. But there is so much bad inline asm code out there, we should
+  // let them be.
+  if (MI->isInlineAsm())
+    return false;
+
   // Don't delete instructions with side effects.
   bool SawStore = false;
   if (!MI->isSafeToMove(TII, 0, SawStore) && !MI->isPHI())
@@ -102,9 +110,14 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
           LivePhysRegs.set(Reg);
       }
 
-    // FIXME: Add live-ins from sucessors to LivePhysRegs. Normally, physregs
-    // are not live across blocks, but some targets (x86) can have flags live
-    // out of a block.
+    // Add live-ins from sucessors to LivePhysRegs. Normally, physregs are not
+    // live across blocks, but some targets (x86) can have flags live out of a
+    // block.
+    for (MachineBasicBlock::succ_iterator S = MBB->succ_begin(),
+           E = MBB->succ_end(); S != E; S++)
+      for (MachineBasicBlock::livein_iterator LI = (*S)->livein_begin();
+           LI != (*S)->livein_end(); LI++)
+        LivePhysRegs.set(*LI);
 
     // Now scan the instructions and delete dead ones, tracking physreg
     // liveness as we go.
@@ -151,7 +164,7 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
         const MachineOperand &MO = MI->getOperand(i);
         if (MO.isReg() && MO.isDef()) {
           unsigned Reg = MO.getReg();
-          if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
+          if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
             LivePhysRegs.reset(Reg);
             // Check the subreg set, not the alias set, because a def
             // of a super-register may still be partially live after
@@ -168,7 +181,7 @@ bool DeadMachineInstructionElim::runOnMachineFunction(MachineFunction &MF) {
         const MachineOperand &MO = MI->getOperand(i);
         if (MO.isReg() && MO.isUse()) {
           unsigned Reg = MO.getReg();
-          if (Reg != 0 && TargetRegisterInfo::isPhysicalRegister(Reg)) {
+          if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
             LivePhysRegs.set(Reg);
             for (const unsigned *AliasSet = TRI->getAliasSet(Reg);
                  *AliasSet; ++AliasSet)