Change MachineBasicBlock's vector of MachineInstr pointers into an

ilist of MachineInstr objects. This allows constant time removal and
insertion of MachineInstr instances from anywhere in each
MachineBasicBlock. It also allows for constant time splicing of
MachineInstrs into or out of MachineBasicBlocks.

llvm-svn: 11340

1 files changed, 19 insertions, 16 deletions

diff --git a/llvm/lib/CodeGen/PHIElimination.cpp b/llvm/lib/CodeGen/PHIElimination.cpp
index afb87e501f2..03a1da9f13d 100644
--- a/llvm/lib/CodeGen/PHIElimination.cpp
+++ b/llvm/lib/CodeGen/PHIElimination.cpp
@@ -61,18 +61,18 @@ const PassInfo *PHIEliminationID = X.getPassInfo();
 /// predecessor basic blocks.
 ///
 bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
-  if (MBB.empty() || MBB.front()->getOpcode() != TargetInstrInfo::PHI)
+  if (MBB.empty() || MBB.front().getOpcode() != TargetInstrInfo::PHI)
     return false;   // Quick exit for normal case...
 
   LiveVariables *LV = getAnalysisToUpdate<LiveVariables>();
   const TargetInstrInfo &MII = MF.getTarget().getInstrInfo();
   const MRegisterInfo *RegInfo = MF.getTarget().getRegisterInfo();
 
-  while (MBB.front()->getOpcode() == TargetInstrInfo::PHI) {
-    MachineInstr *MI = MBB.front();
+  while (MBB.front().getOpcode() == TargetInstrInfo::PHI) {
     // Unlink the PHI node from the basic block... but don't delete the PHI yet
-    MBB.erase(MBB.begin());
-
+    MachineBasicBlock::iterator begin = MBB.begin();
+    MachineInstr *MI = MBB.remove(begin);
+    
     assert(MRegisterInfo::isVirtualRegister(MI->getOperand(0).getReg()) &&
            "PHI node doesn't write virt reg?");
 
@@ -88,13 +88,13 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
     //
     MachineBasicBlock::iterator AfterPHIsIt = MBB.begin();
     while (AfterPHIsIt != MBB.end() &&
-           (*AfterPHIsIt)->getOpcode() == TargetInstrInfo::PHI)
+           AfterPHIsIt->getOpcode() == TargetInstrInfo::PHI)
       ++AfterPHIsIt;    // Skip over all of the PHI nodes...
     RegInfo->copyRegToReg(MBB, AfterPHIsIt, DestReg, IncomingReg, RC);
     
     // Update live variable information if there is any...
     if (LV) {
-      MachineInstr *PHICopy = *(AfterPHIsIt-1);
+      MachineInstr *PHICopy = --AfterPHIsIt;
 
       // Add information to LiveVariables to know that the incoming value is
       // killed.  Note that because the value is defined in several places (once
@@ -149,13 +149,13 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
       if (I != opBlock.begin()) {  // Handle empty blocks
         --I;
         // must backtrack over ALL the branches in the previous block
-        while (MII.isTerminatorInstr((*I)->getOpcode()) &&
+        while (MII.isTerminatorInstr(I->getOpcode()) &&
                I != opBlock.begin())
           --I;
         
         // move back to the first branch instruction so new instructions
         // are inserted right in front of it and not in front of a non-branch
-        if (!MII.isTerminatorInstr((*I)->getOpcode()))
+        if (!MII.isTerminatorInstr(I->getOpcode()))
           ++I;
       }
       
@@ -171,7 +171,8 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
       bool HaveNotEmitted = true;
       
       if (I != opBlock.begin()) {
-        MachineInstr *PrevInst = *(I-1);
+        MachineBasicBlock::iterator PrevInst = I;
+        --PrevInst;
         for (unsigned i = 0, e = PrevInst->getNumOperands(); i != e; ++i) {
           MachineOperand &MO = PrevInst->getOperand(i);
           if (MO.isRegister() && MO.getReg() == IncomingReg)
@@ -238,10 +239,10 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
             // Loop over all of the PHIs in this successor, checking to see if
             // the register is being used...
             for (MachineBasicBlock::iterator BBI = MBB->begin(), E=MBB->end();
-                 BBI != E && (*BBI)->getOpcode() == TargetInstrInfo::PHI;
+                 BBI != E && BBI->getOpcode() == TargetInstrInfo::PHI;
                  ++BBI)
-              for (unsigned i = 1, e = (*BBI)->getNumOperands(); i < e; i += 2)
-                if ((*BBI)->getOperand(i).getReg() == SrcReg) {
+              for (unsigned i = 1, e = BBI->getNumOperands(); i < e; i += 2)
+                if (BBI->getOperand(i).getReg() == SrcReg) {
                   ValueIsLive = true;
                   break;
                 }
@@ -251,8 +252,11 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
           // we can add a kill marker to the copy we inserted saying that it
           // kills the incoming value!
           //
-          if (!ValueIsLive)
-            LV->addVirtualRegisterKilled(SrcReg, &opBlock, *(I-1));
+          if (!ValueIsLive) {
+            MachineBasicBlock::iterator Prev = I;
+            --Prev;
+            LV->addVirtualRegisterKilled(SrcReg, &opBlock, Prev);
+          }
         }
       }
     }
@@ -260,7 +264,6 @@ bool PNE::EliminatePHINodes(MachineFunction &MF, MachineBasicBlock &MBB) {
     // really delete the PHI instruction now!
     delete MI;
   }
-
   return true;
 }