Confusing comment typo.

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

diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index 6bc7e37e3d879a3752a0638bc9ece62ad8f402ac..a7439b5129b5bafa6ef1cb6e18fd3ea06c33dc7b 100644 (file)
--- 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
@@ -79,6 +85,7 @@ STATISTIC(NumBitcasts,   "Number of bitcasts eliminated");
 STATISTIC(NumCmps,       "Number of compares eliminated");
 STATISTIC(NumImmFold,    "Number of move immediate folded");
 STATISTIC(NumLoadFold,   "Number of loads folded");
+STATISTIC(NumSelects,    "Number of selects optimized");
 
 namespace {
   class PeepholeOptimizer : public MachineFunctionPass {
@@ -109,6 +116,7 @@ namespace {
     bool optimizeCmpInstr(MachineInstr *MI, MachineBasicBlock *MBB);
     bool optimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
                           SmallPtrSet<MachineInstr*, 8> &LocalMIs);
+    bool optimizeSelect(MachineInstr *MI);
     bool isMoveImmediate(MachineInstr *MI,
                          SmallSet<unsigned, 4> &ImmDefRegs,
                          DenseMap<unsigned, MachineInstr*> &ImmDefMIs);
@@ -386,6 +394,23 @@ bool PeepholeOptimizer::optimizeCmpInstr(MachineInstr *MI,
   return false;
 }
 
+/// Optimize a select instruction.
+bool PeepholeOptimizer::optimizeSelect(MachineInstr *MI) {
+  unsigned TrueOp = 0;
+  unsigned FalseOp = 0;
+  bool Optimizable = false;
+  SmallVector<MachineOperand, 4> Cond;
+  if (TII->analyzeSelect(MI, Cond, TrueOp, FalseOp, Optimizable))
+    return false;
+  if (!Optimizable)
+    return false;
+  if (!TII->optimizeSelect(MI))
+    return false;
+  MI->eraseFromParent();
+  ++NumSelects;
+  return true;
+}
+
 /// isLoadFoldable - Check whether MI is a candidate for folding into a later
 /// instruction. We only fold loads to virtual registers and the virtual
 /// register defined has a single use.
@@ -454,6 +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;
 
@@ -477,11 +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
@@ -490,34 +518,29 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
           MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
           MI->hasUnmodeledSideEffects()) {
         FoldAsLoadDefReg = 0;
-        ++MII;
         continue;
       }
       if (MI->mayStore() || MI->isCall())
         FoldAsLoadDefReg = 0;
 
-      if (MI->isBitcast()) {
-        if (optimizeBitcastInstr(MI, MBB)) {
-          // MI is deleted.
-          LocalMIs.erase(MI);
-          Changed = true;
-          MII = First ? I->begin() : llvm::next(PMII);
-          continue;
-        }
-      } else if (MI->isCompare()) {
-        if (optimizeCmpInstr(MI, MBB)) {
-          // MI is deleted.
-          LocalMIs.erase(MI);
-          Changed = true;
-          MII = First ? I->begin() : llvm::next(PMII);
-          continue;
-        }
+      if ((MI->isBitcast() && optimizeBitcastInstr(MI, MBB)) ||
+          (MI->isCompare() && optimizeCmpInstr(MI, MBB)) ||
+          (MI->isSelect() && optimizeSelect(MI))) {
+        // MI is deleted.
+        LocalMIs.erase(MI);
+        Changed = true;
+        continue;
       }
 
       if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
         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);
       }
@@ -533,6 +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);
@@ -542,14 +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;
     }
   }