Move some of the InlineSpiller rematerialization code into LiveRangeEdit.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@116951 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/InlineSpiller.cpp

@@ -49,10 +49,7 @@ class InlineSpiller : public Spiller {
   const TargetRegisterClass *rc_;
   int stackSlot_;
 
-  // Values of the current interval that can potentially remat.
-  SmallPtrSet<VNInfo*, 8> reMattable_;
-
-  // Values in reMattable_ that failed to remat at some point.
+  // Values that failed to remat at some point.
   SmallPtrSet<VNInfo*, 8> usedValues_;
 
   ~InlineSpiller() {}
@@ -136,6 +133,7 @@ bool InlineSpiller::split() {
 bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
   SlotIndex UseIdx = lis_.getInstructionIndex(MI).getUseIndex();
   VNInfo *OrigVNI = edit_->getParent().getVNInfoAt(UseIdx);
+
   if (!OrigVNI) {
     DEBUG(dbgs() << "\tadding <undef> flags: ");
     for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
@@ -146,20 +144,17 @@ bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
     DEBUG(dbgs() << UseIdx << '\t' << *MI);
     return true;
   }
-  if (!reMattable_.count(OrigVNI)) {
-    DEBUG(dbgs() << "\tusing non-remat valno " << OrigVNI->id << ": "
-                 << UseIdx << '\t' << *MI);
-    return false;
-  }
-  MachineInstr *OrigMI = lis_.getInstructionFromIndex(OrigVNI->def);
-  if (!edit_->allUsesAvailableAt(OrigMI, OrigVNI->def, UseIdx, lis_)) {
+
+  LiveRangeEdit::Remat RM = edit_->canRematerializeAt(OrigVNI, UseIdx, false,
+                                                      lis_);
+  if (!RM) {
     usedValues_.insert(OrigVNI);
     DEBUG(dbgs() << "\tcannot remat for " << UseIdx << '\t' << *MI);
     return false;
   }
 
-  // If the instruction also writes edit_->getReg(), it had better not require the same
-  // register for uses and defs.
+  // If the instruction also writes edit_->getReg(), it had better not require
+  // the same register for uses and defs.
   bool Reads, Writes;
   SmallVector<unsigned, 8> Ops;
   tie(Reads, Writes) = MI->readsWritesVirtualRegister(edit_->getReg(), &Ops);
@@ -179,11 +174,9 @@ bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
   NewLI.markNotSpillable();
 
   // Finally we can rematerialize OrigMI before MI.
-  MachineBasicBlock &MBB = *MI->getParent();
-  tii_.reMaterialize(MBB, MI, NewLI.reg, 0, OrigMI, tri_);
-  MachineBasicBlock::iterator RematMI = MI;
-  SlotIndex DefIdx = lis_.InsertMachineInstrInMaps(--RematMI).getDefIndex();
-  DEBUG(dbgs() << "\tremat:  " << DefIdx << '\t' << *RematMI);
+  SlotIndex DefIdx = edit_->rematerializeAt(*MI->getParent(), MI, NewLI.reg, RM,
+                                            lis_, tii_, tri_);
+  DEBUG(dbgs() << "\tremat:  " << DefIdx << '\n');
 
   // Replace operands
   for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
@@ -205,23 +198,11 @@ bool InlineSpiller::reMaterializeFor(MachineBasicBlock::iterator MI) {
 /// and trim the live ranges after.
 void InlineSpiller::reMaterializeAll() {
   // Do a quick scan of the interval values to find if any are remattable.
-  reMattable_.clear();
-  usedValues_.clear();
-  for (LiveInterval::const_vni_iterator I = edit_->getParent().vni_begin(),
-       E = edit_->getParent().vni_end(); I != E; ++I) {
-    VNInfo *VNI = *I;
-    if (VNI->isUnused())
-      continue;
-    MachineInstr *DefMI = lis_.getInstructionFromIndex(VNI->def);
-    if (!DefMI || !tii_.isTriviallyReMaterializable(DefMI))
-      continue;
-    reMattable_.insert(VNI);
-  }
-
-  // Often, no defs are remattable.
-  if (reMattable_.empty())
+  if (!edit_->anyRematerializable(lis_, tii_, 0))
     return;
 
+  usedValues_.clear();
+
   // Try to remat before all uses of edit_->getReg().
   bool anyRemat = false;
   for (MachineRegisterInfo::use_nodbg_iterator
@@ -234,10 +215,11 @@ void InlineSpiller::reMaterializeAll() {
 
   // Remove any values that were completely rematted.
   bool anyRemoved = false;
-  for (SmallPtrSet<VNInfo*, 8>::iterator I = reMattable_.begin(),
-       E = reMattable_.end(); I != E; ++I) {
+  for (LiveInterval::vni_iterator I = edit_->getParent().vni_begin(),
+       E = edit_->getParent().vni_end(); I != E; ++I) {
     VNInfo *VNI = *I;
-    if (VNI->hasPHIKill() || usedValues_.count(VNI))
+    if (VNI->hasPHIKill() || !edit_->didRematerialize(VNI) ||
+        usedValues_.count(VNI))
       continue;
     MachineInstr *DefMI = lis_.getInstructionFromIndex(VNI->def);
     DEBUG(dbgs() << "\tremoving dead def: " << VNI->def << '\t' << *DefMI);

lib/CodeGen/LiveRangeEdit.cpp

@@ -15,6 +15,7 @@
 #include "VirtRegMap.h"
 #include "llvm/CodeGen/LiveIntervalAnalysis.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
 
 using namespace llvm;
 
@@ -38,6 +39,31 @@ LiveInterval &LiveRangeEdit::create(MachineRegisterInfo &mri,
   return li;
 }
 
+void LiveRangeEdit::scanRemattable(LiveIntervals &lis,
+                                   const TargetInstrInfo &tii,
+                                   AliasAnalysis *aa) {
+  for (LiveInterval::vni_iterator I = parent_.vni_begin(),
+       E = parent_.vni_end(); I != E; ++I) {
+    VNInfo *VNI = *I;
+    if (VNI->isUnused())
+      continue;
+    MachineInstr *DefMI = lis.getInstructionFromIndex(VNI->def);
+    if (!DefMI)
+      continue;
+    if (tii.isTriviallyReMaterializable(DefMI, aa))
+      remattable_.insert(VNI);
+  }
+  scannedRemattable_ = true;
+}
+
+bool LiveRangeEdit::anyRematerializable(LiveIntervals &lis,
+                                        const TargetInstrInfo &tii,
+                                        AliasAnalysis *aa) {
+  if (!scannedRemattable_)
+    scanRemattable(lis, tii, aa);
+  return !remattable_.empty();
+}
+
 /// allUsesAvailableAt - Return true if all registers used by OrigMI at
 /// OrigIdx are also available with the same value at UseIdx.
 bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
@@ -71,3 +97,47 @@ bool LiveRangeEdit::allUsesAvailableAt(const MachineInstr *OrigMI,
   return true;
 }
 
+LiveRangeEdit::Remat LiveRangeEdit::canRematerializeAt(VNInfo *ParentVNI,
+                                                       SlotIndex UseIdx,
+                                                       bool cheapAsAMove,
+                                                       LiveIntervals &lis) {
+  assert(scannedRemattable_ && "Call anyRematerializable first");
+  Remat RM = { 0, 0 };
+
+  // We could remat an undefined value as IMPLICIT_DEF, but all that should have
+  // been taken care of earlier.
+  if (!(RM.ParentVNI = parent_.getVNInfoAt(UseIdx)))
+    return RM;
+
+  // Use scanRemattable info.
+  if (!remattable_.count(RM.ParentVNI))
+    return RM;
+
+  // No defining instruction.
+  MachineInstr *OrigMI = lis.getInstructionFromIndex(RM.ParentVNI->def);
+  assert(OrigMI && "Defining instruction for remattable value disappeared");
+
+  // If only cheap remats were requested, bail out early.
+  if (cheapAsAMove && !OrigMI->getDesc().isAsCheapAsAMove())
+    return RM;
+
+  // Verify that all used registers are available with the same values.
+  if (!allUsesAvailableAt(OrigMI, RM.ParentVNI->def, UseIdx, lis))
+    return RM;
+
+  RM.OrigMI = OrigMI;
+  return RM;
+}
+
+SlotIndex LiveRangeEdit::rematerializeAt(MachineBasicBlock &MBB,
+                                         MachineBasicBlock::iterator MI,
+                                         unsigned DestReg,
+                                         const Remat &RM,
+                                         LiveIntervals &lis,
+                                         const TargetInstrInfo &tii,
+                                         const TargetRegisterInfo &tri) {
+  assert(RM.OrigMI && "Invalid remat");
+  tii.reMaterialize(MBB, MI, DestReg, 0, RM.OrigMI, tri);
+  return lis.InsertMachineInstrInMaps(--MI).getDefIndex();
+}
+

lib/CodeGen/LiveRangeEdit.h

@@ -19,9 +19,11 @@
 #define LLVM_CODEGEN_LIVERANGEEDIT_H
 
 #include "llvm/CodeGen/LiveInterval.h"
+#include "llvm/ADT/SmallPtrSet.h"
 
 namespace llvm {
 
+class AliasAnalysis;
 class LiveIntervals;
 class MachineRegisterInfo;
 class VirtRegMap;
@@ -34,6 +36,27 @@ class LiveRangeEdit {
   /// firstNew_ - Index of the first register added to newRegs_.
   const unsigned firstNew_;
 
+  /// scannedRemattable_ - true when remattable values have been identified.
+  bool scannedRemattable_;
+
+  /// remattable_ - Values defined by remattable instructions as identified by
+  /// tii.isTriviallyReMaterializable().
+  SmallPtrSet<VNInfo*,4> remattable_;
+
+  /// rematted_ - Values that were actually rematted, and so need to have their
+  /// live range trimmed or entirely removed.
+  SmallPtrSet<VNInfo*,4> rematted_;
+
+  /// scanRemattable - Identify the parent_ values that may rematerialize.
+  void scanRemattable(LiveIntervals &lis,
+                      const TargetInstrInfo &tii,
+                      AliasAnalysis *aa);
+
+  /// allUsesAvailableAt - Return true if all registers used by OrigMI at
+  /// OrigIdx are also available with the same value at UseIdx.
+  bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
+                          SlotIndex UseIdx, LiveIntervals &lis);
+
 public:
   /// Create a LiveRangeEdit for breaking down parent into smaller pieces.
   /// @param parent The register being spilled or split.
@@ -45,7 +68,7 @@ public:
                 SmallVectorImpl<LiveInterval*> &newRegs,
                 const SmallVectorImpl<LiveInterval*> &uselessRegs)
     : parent_(parent), newRegs_(newRegs), uselessRegs_(uselessRegs),
-      firstNew_(newRegs.size()) {}
+      firstNew_(newRegs.size()), scannedRemattable_(false) {}
 
   LiveInterval &getParent() const { return parent_; }
   unsigned getReg() const { return parent_.reg; }
@@ -63,11 +86,43 @@ public:
   /// parent.
   LiveInterval &create(MachineRegisterInfo&, LiveIntervals&, VirtRegMap&);
 
-  /// allUsesAvailableAt - Return true if all registers used by OrigMI at
-  /// OrigIdx are also available with the same value at UseIdx.
-  bool allUsesAvailableAt(const MachineInstr *OrigMI, SlotIndex OrigIdx,
-                          SlotIndex UseIdx, LiveIntervals &lis);
+  /// anyRematerializable - Return true if any parent values may be
+  /// rematerializable.
+  /// This function must be called before ny rematerialization is attempted.
+  bool anyRematerializable(LiveIntervals&, const TargetInstrInfo&,
+                           AliasAnalysis*);
 
+  /// Remat - Information needed to rematerialize at a specific location.
+  struct Remat {
+    VNInfo *ParentVNI;      // parent_'s value at the remat location.
+    MachineInstr *OrigMI;   // Instruction defining ParentVNI.
+    operator bool() const { return OrigMI; }
+  };
+
+  /// canRematerializeAt - Determine if ParentVNI can be rematerialized at
+  /// UseIdx. It is assumed that parent_.getVNINfoAt(UseIdx) == ParentVNI.
+  /// When cheapAsAMove is set, only cheap remats are allowed.
+  Remat canRematerializeAt(VNInfo *ParentVNI,
+                           SlotIndex UseIdx,
+                           bool cheapAsAMove,
+                           LiveIntervals &lis);
+
+  /// rematerializeAt - Rematerialize RM.ParentVNI into DestReg by inserting an
+  /// instruction into MBB before MI. The new instruction is mapped, but
+  /// liveness is not updated.
+  /// Return the SlotIndex of the new instruction.
+  SlotIndex rematerializeAt(MachineBasicBlock &MBB,
+                            MachineBasicBlock::iterator MI,
+                            unsigned DestReg,
+                            const Remat &RM,
+                            LiveIntervals&,
+                            const TargetInstrInfo&,
+                            const TargetRegisterInfo&);
+
+  /// didRematerialize - Return true if ParentVNI was rematerialized anywhere.
+  bool didRematerialize(VNInfo *ParentVNI) const {
+    return rematted_.count(ParentVNI);
+  }
 };
 
 }