[DAGCombiner] Tidy up ConstantFP commutation. NFCI

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

diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 2b7543f2c370329f8b3857c18dbd897e250a9c74..2c937926d0a7eac09f9a263459102e82c97e21b6 100644 (file)
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -29,6 +29,7 @@
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
 #include "llvm/Target/TargetInstrInfo.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include <algorithm>
@@ -46,6 +47,10 @@ SplitAllCriticalEdges("phi-elim-split-all-critical-edges", cl::init(false),
                       cl::Hidden, cl::desc("Split all critical edges during "
                                            "PHI elimination"));
 
+static cl::opt<bool> NoPhiElimLiveOutEarlyExit(
+    "no-phi-elim-live-out-early-exit", cl::init(false), cl::Hidden,
+    cl::desc("Do not use an early exit if isLiveOutPastPHIs returns true."));
+
 namespace {
   class PHIElimination : public MachineFunctionPass {
     MachineRegisterInfo *MRI; // Machine register information
@@ -83,8 +88,8 @@ namespace {
 
     // These functions are temporary abstractions around LiveVariables and
     // LiveIntervals, so they can go away when LiveVariables does.
-    bool isLiveIn(unsigned Reg, MachineBasicBlock *MBB);
-    bool isLiveOutPastPHIs(unsigned Reg, MachineBasicBlock *MBB);
+    bool isLiveIn(unsigned Reg, const MachineBasicBlock *MBB);
+    bool isLiveOutPastPHIs(unsigned Reg, const MachineBasicBlock *MBB);
 
     typedef std::pair<unsigned, unsigned> BBVRegPair;
     typedef DenseMap<BBVRegPair, unsigned> VRegPHIUse;
@@ -138,16 +143,16 @@ bool PHIElimination::runOnMachineFunction(MachineFunction &MF) {
   // updating LiveIntervals, so we disable it.
   if (!DisableEdgeSplitting && (LV || LIS)) {
     MachineLoopInfo *MLI = getAnalysisIfAvailable<MachineLoopInfo>();
-    for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
-      Changed |= SplitPHIEdges(MF, *I, MLI);
+    for (auto &MBB : MF)
+      Changed |= SplitPHIEdges(MF, MBB, MLI);
   }
 
   // Populate VRegPHIUseCount
   analyzePHINodes(MF);
 
   // Eliminate PHI instructions by inserting copies into predecessor blocks.
-  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I)
-    Changed |= EliminatePHINodes(MF, *I);
+  for (auto &MBB : MF)
+    Changed |= EliminatePHINodes(MF, MBB);
 
   // Remove dead IMPLICIT_DEF instructions.
   for (MachineInstr *DefMI : ImpDefs) {
@@ -367,7 +372,7 @@ void PHIElimination::LowerPHINode(MachineBasicBlock &MBB,
     // Check to make sure we haven't already emitted the copy for this block.
     // This can happen because PHI nodes may have multiple entries for the same
     // basic block.
-    if (!MBBsInsertedInto.insert(&opBlock))
+    if (!MBBsInsertedInto.insert(&opBlock).second)
       continue;  // If the copy has already been emitted, we're done.
 
     // Find a safe location to insert the copy, this may be the first terminator
@@ -543,7 +548,7 @@ void PHIElimination::analyzePHINodes(const MachineFunction& MF) {
 bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
                                    MachineBasicBlock &MBB,
                                    MachineLoopInfo *MLI) {
-  if (MBB.empty() || !MBB.front().isPHI() || MBB.isLandingPad())
+  if (MBB.empty() || !MBB.front().isPHI() || MBB.isEHPad())
     return false;   // Quick exit for basic blocks without PHIs.
 
   const MachineLoop *CurLoop = MLI ? MLI->getLoopFor(&MBB) : nullptr;
@@ -573,12 +578,14 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
       // there is a risk it may not be coalesced away.
       //
       // If the copy would be a kill, there is no need to split the edge.
-      if (!isLiveOutPastPHIs(Reg, PreMBB) && !SplitAllCriticalEdges)
+      bool ShouldSplit = isLiveOutPastPHIs(Reg, PreMBB);
+      if (!ShouldSplit && !NoPhiElimLiveOutEarlyExit)
         continue;
-
-      DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#"
-                   << PreMBB->getNumber() << " -> BB#" << MBB.getNumber()
-                   << ": " << *BBI);
+      if (ShouldSplit) {
+        DEBUG(dbgs() << PrintReg(Reg) << " live-out before critical edge BB#"
+                     << PreMBB->getNumber() << " -> BB#" << MBB.getNumber()
+                     << ": " << *BBI);
+      }
 
       // If Reg is not live-in to MBB, it means it must be live-in to some
       // other PreMBB successor, and we can avoid the interference by splitting
@@ -588,7 +595,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
       // is likely to be left after coalescing. If we are looking at a loop
       // exiting edge, split it so we won't insert code in the loop, otherwise
       // don't bother.
-      bool ShouldSplit = !isLiveIn(Reg, &MBB) || SplitAllCriticalEdges;
+      ShouldSplit = ShouldSplit && !isLiveIn(Reg, &MBB);
 
       // Check for a loop exiting edge.
       if (!ShouldSplit && CurLoop != PreLoop) {
@@ -603,7 +610,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
         // Split unless this edge is entering CurLoop from an outer loop.
         ShouldSplit = PreLoop && !PreLoop->contains(CurLoop);
       }
-      if (!ShouldSplit)
+      if (!ShouldSplit && !SplitAllCriticalEdges)
         continue;
       if (!PreMBB->SplitCriticalEdge(&MBB, this)) {
         DEBUG(dbgs() << "Failed to split critical edge.\n");
@@ -616,7 +623,7 @@ bool PHIElimination::SplitPHIEdges(MachineFunction &MF,
   return Changed;
 }
 
-bool PHIElimination::isLiveIn(unsigned Reg, MachineBasicBlock *MBB) {
+bool PHIElimination::isLiveIn(unsigned Reg, const MachineBasicBlock *MBB) {
   assert((LV || LIS) &&
          "isLiveIn() requires either LiveVariables or LiveIntervals");
   if (LIS)
@@ -625,7 +632,8 @@ bool PHIElimination::isLiveIn(unsigned Reg, MachineBasicBlock *MBB) {
     return LV->isLiveIn(Reg, *MBB);
 }
 
-bool PHIElimination::isLiveOutPastPHIs(unsigned Reg, MachineBasicBlock *MBB) {
+bool PHIElimination::isLiveOutPastPHIs(unsigned Reg,
+                                       const MachineBasicBlock *MBB) {
   assert((LV || LIS) &&
          "isLiveOutPastPHIs() requires either LiveVariables or LiveIntervals");
   // LiveVariables considers uses in PHIs to be in the predecessor basic block,
@@ -635,11 +643,9 @@ bool PHIElimination::isLiveOutPastPHIs(unsigned Reg, MachineBasicBlock *MBB) {
   // out of the block.
   if (LIS) {
     const LiveInterval &LI = LIS->getInterval(Reg);
-    for (MachineBasicBlock::succ_iterator SI = MBB->succ_begin(),
-         SE = MBB->succ_end(); SI != SE; ++SI) {
-      if (LI.liveAt(LIS->getMBBStartIdx(*SI)))
+    for (const MachineBasicBlock *SI : MBB->successors())
+      if (LI.liveAt(LIS->getMBBStartIdx(SI)))
         return true;
-    }
     return false;
   } else {
     return LV->isLiveOut(Reg, *MBB);