X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=lib%2FCodeGen%2FPeepholeOptimizer.cpp;h=a7439b5129b5bafa6ef1cb6e18fd3ea06c33dc7b;hb=0a230e0d985625a3909cb78fd867a3abaf434565;hp=096df7bf6a18adfb658c7d4779e9bcf7af9806e8;hpb=f2c64ef519b38a4328809b27b4a3a8e0c26e9709;p=oota-llvm.git

diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index 096df7bf6a1..a7439b5129b 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/lib/CodeGen/PeepholeOptimizer.cpp
@@ -49,20 +49,26 @@
 //     v1 = bitcast v0
 //        = v0
 //
+// - Optimize Loads:
+//
+//     Loads that can be folded into a later instruction. A load is foldable
+//     if it loads to virtual registers and the virtual register defined has 
+//     a single use.
 //===----------------------------------------------------------------------===//
 
 #define DEBUG_TYPE "peephole-opt"
 #include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetRegisterInfo.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/Statistic.h"
 using namespace llvm;
 
 // Optimize Extensions
@@ -473,6 +479,9 @@ bool PeepholeOptimizer::foldImmediate(MachineInstr *MI, MachineBasicBlock *MBB,
 }
 
 bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
+  DEBUG(dbgs() << "********** PEEPHOLE OPTIMIZER **********\n");
+  DEBUG(dbgs() << "********** Function: " << MF.getName() << '\n');
+
   if (DisablePeephole)
     return false;
 
@@ -496,11 +505,11 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
     ImmDefMIs.clear();
     FoldAsLoadDefReg = 0;
 
-    bool First = true;
-    MachineBasicBlock::iterator PMII;
     for (MachineBasicBlock::iterator
            MII = I->begin(), MIE = I->end(); MII != MIE; ) {
       MachineInstr *MI = &*MII;
+      // We may be erasing MI below, increment MII now.
+      ++MII;
       LocalMIs.insert(MI);
 
       // If there exists an instruction which belongs to the following
@@ -509,7 +518,6 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
           MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
           MI->hasUnmodeledSideEffects()) {
         FoldAsLoadDefReg = 0;
-        ++MII;
         continue;
       }
       if (MI->mayStore() || MI->isCall())
@@ -521,7 +529,6 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
         // MI is deleted.
         LocalMIs.erase(MI);
         Changed = true;
-        MII = First ? I->begin() : llvm::next(PMII);
         continue;
       }
 
@@ -529,6 +536,11 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
         SeenMoveImm = true;
       } else {
         Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
+        // optimizeExtInstr might have created new instructions after MI
+        // and before the already incremented MII. Adjust MII so that the
+        // next iteration sees the new instructions.
+        MII = MI;
+        ++MII;
         if (SeenMoveImm)
           Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
       }
@@ -544,6 +556,8 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
                                                       FoldAsLoadDefReg, DefMI);
         if (FoldMI) {
           // Update LocalMIs since we replaced MI with FoldMI and deleted DefMI.
+          DEBUG(dbgs() << "Replacing: " << *MI);
+          DEBUG(dbgs() << "     With: " << *FoldMI);
           LocalMIs.erase(MI);
           LocalMIs.erase(DefMI);
           LocalMIs.insert(FoldMI);
@@ -553,14 +567,9 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
 
           // MI is replaced with FoldMI.
           Changed = true;
-          PMII = FoldMI;
-          MII = llvm::next(PMII);
           continue;
         }
       }
-      First = false;
-      PMII = MII;
-      ++MII;
     }
   }