Allow the register scavenger to spill multiple registers

This patch lets the register scavenger make use of multiple spill slots in
order to guarantee that it will be able to provide multiple registers
simultaneously.

To support this, the RS's API has changed slightly: setScavengingFrameIndex /
getScavengingFrameIndex have been replaced by addScavengingFrameIndex /
isScavengingFrameIndex / getScavengingFrameIndices.

In forthcoming commits, the PowerPC backend will use this capability in order
to implement the spilling of condition registers, and some special-purpose
registers, without relying on r0 being reserved. In some cases, spilling these
registers requires two GPRs: one for addressing and one to hold the value being
transferred.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@177774 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/llvm/CodeGen/RegisterScavenging.h b/include/llvm/CodeGen/RegisterScavenging.h
index a2b1533e5d65375d1987dc546d3cf5864769ce86..babb96b9624ca94d5350e34fa81dc2ab111d090a 100644 (file)
--- a/include/llvm/CodeGen/RegisterScavenging.h
+++ b/include/llvm/CodeGen/RegisterScavenging.h
@@ -40,17 +40,23 @@ class RegScavenger {
   /// registers.
   bool Tracking;
 
-  /// ScavengingFrameIndex - Special spill slot used for scavenging a register
-  /// post register allocation.
-  int ScavengingFrameIndex;
+  /// Information on scavenged registers (held in a spill slot).
+  struct ScavengedInfo {
+    ScavengedInfo(int FI) : FrameIndex(FI), Reg(0), Restore(NULL) {}
 
-  /// ScavengedReg - If none zero, the specific register is currently being
-  /// scavenged. That is, it is spilled to the special scavenging stack slot.
-  unsigned ScavengedReg;
+    /// A spill slot used for scavenging a register post register allocation.
+    int FrameIndex;
 
-  /// ScavengeRestore - Instruction that restores the scavenged register from
-  /// stack.
-  const MachineInstr *ScavengeRestore;
+    /// If non-zero, the specific register is currently being
+    /// scavenged. That is, it is spilled to this scavenging stack slot.
+    unsigned Reg;
+
+    /// The instruction that restores the scavenged register from stack.
+    const MachineInstr *Restore;
+  };
+
+  /// A vector of information on scavenged registers.
+  SmallVector<ScavengedInfo, 2> Scavenged;
 
   /// CalleeSavedrRegs - A bitvector of callee saved registers for the target.
   ///
@@ -67,8 +73,7 @@ class RegScavenger {
 
 public:
   RegScavenger()
-    : MBB(NULL), NumPhysRegs(0), Tracking(false),
-      ScavengingFrameIndex(-1), ScavengedReg(0) {}
+    : MBB(NULL), NumPhysRegs(0), Tracking(false) {}
 
   /// enterBasicBlock - Start tracking liveness from the begin of the specific
   /// basic block.
@@ -103,10 +108,27 @@ public:
   /// Return 0 if none is found.
   unsigned FindUnusedReg(const TargetRegisterClass *RegClass) const;
 
-  /// setScavengingFrameIndex / getScavengingFrameIndex - accessor and setter of
-  /// ScavengingFrameIndex.
-  void setScavengingFrameIndex(int FI) { ScavengingFrameIndex = FI; }
-  int getScavengingFrameIndex() const { return ScavengingFrameIndex; }
+  /// Add a scavenging frame index.
+  void addScavengingFrameIndex(int FI) {
+    Scavenged.push_back(ScavengedInfo(FI));
+  }
+
+  /// Query whether a frame index is a scavenging frame index.
+  bool isScavengingFrameIndex(int FI) const {
+    for (SmallVector<ScavengedInfo, 2>::const_iterator I = Scavenged.begin(),
+         IE = Scavenged.end(); I != IE; ++I)
+      if (I->FrameIndex == FI)
+        return true;
+
+    return false;
+  }
+
+  /// Get an array of scavenging frame indices.
+  void getScavengingFrameIndices(SmallVectorImpl<int> &A) const {
+    for (SmallVector<ScavengedInfo, 2>::const_iterator I = Scavenged.begin(),
+         IE = Scavenged.end(); I != IE; ++I)
+      A.push_back(I->FrameIndex);
+  }
 
   /// scavengeRegister - Make a register of the specific register class
   /// available and do the appropriate bookkeeping. SPAdj is the stack

diff --git a/lib/CodeGen/PrologEpilogInserter.cpp b/lib/CodeGen/PrologEpilogInserter.cpp
index 855a8c5f926ed543ce2536348f2029db4362a4fa..413ce91ead21d00cac0cbd99b4dbce6661dbea26 100644 (file)
--- a/lib/CodeGen/PrologEpilogInserter.cpp
+++ b/lib/CodeGen/PrologEpilogInserter.cpp
@@ -548,9 +548,11 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
   if (RS && TFI.hasFP(Fn) && RegInfo->useFPForScavengingIndex(Fn) &&
       !RegInfo->needsStackRealignment(Fn)) {
-    int SFI = RS->getScavengingFrameIndex();
-    if (SFI >= 0)
-      AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
+    SmallVector<int, 2> SFIs;
+    RS->getScavengingFrameIndices(SFIs);
+    for (SmallVector<int, 2>::iterator I = SFIs.begin(),
+         IE = SFIs.end(); I != IE; ++I)
+      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
   }
 
   // FIXME: Once this is working, then enable flag will change to a target
@@ -593,7 +595,7 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
         continue;
       if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
         continue;
-      if (RS && (int)i == RS->getScavengingFrameIndex())
+      if (RS && RS->isScavengingFrameIndex((int)i))
         continue;
       if (MFI->isDeadObjectIndex(i))
         continue;
@@ -615,7 +617,7 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
       continue;
     if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
       continue;
-    if (RS && (int)i == RS->getScavengingFrameIndex())
+    if (RS && RS->isScavengingFrameIndex((int)i))
       continue;
     if (MFI->isDeadObjectIndex(i))
       continue;
@@ -631,9 +633,11 @@ void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
   // stack pointer.
   if (RS && (!TFI.hasFP(Fn) || RegInfo->needsStackRealignment(Fn) ||
              !RegInfo->useFPForScavengingIndex(Fn))) {
-    int SFI = RS->getScavengingFrameIndex();
-    if (SFI >= 0)
-      AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
+    SmallVector<int, 2> SFIs;
+    RS->getScavengingFrameIndices(SFIs);
+    for (SmallVector<int, 2>::iterator I = SFIs.begin(),
+         IE = SFIs.end(); I != IE; ++I)
+      AdjustStackOffset(MFI, *I, StackGrowsDown, Offset, MaxAlign);
   }
 
   if (!TFI.targetHandlesStackFrameRounding()) {

diff --git a/lib/CodeGen/RegisterScavenging.cpp b/lib/CodeGen/RegisterScavenging.cpp
index d0d30e8f946d49b5d8659d46ee0985802d424ea2..be338540600d7b195639bae6a49b66dea8cd10cd 100644 (file)
--- a/lib/CodeGen/RegisterScavenging.cpp
+++ b/lib/CodeGen/RegisterScavenging.cpp
@@ -45,8 +45,11 @@ bool RegScavenger::isAliasUsed(unsigned Reg) const {
 }
 
 void RegScavenger::initRegState() {
-  ScavengedReg = 0;
-  ScavengeRestore = NULL;
+  for (SmallVector<ScavengedInfo, 2>::iterator I = Scavenged.begin(),
+       IE = Scavenged.end(); I != IE; ++I) {
+    I->Reg = 0;
+    I->Restore = NULL;
+  }
 
   // All registers started out unused.
   RegsAvailable.set();
@@ -120,9 +123,13 @@ void RegScavenger::forward() {
 
   MachineInstr *MI = MBBI;
 
-  if (MI == ScavengeRestore) {
-    ScavengedReg = 0;
-    ScavengeRestore = NULL;
+  for (SmallVector<ScavengedInfo, 2>::iterator I = Scavenged.begin(),
+       IE = Scavenged.end(); I != IE; ++I) {
+    if (I->Restore != MI)
+      continue;
+
+    I->Reg = 0;
+    I->Restore = NULL;
   }
 
   if (MI->isDebugValue())
@@ -358,36 +365,44 @@ unsigned RegScavenger::scavengeRegister(const TargetRegisterClass *RC,
     return SReg;
   }
 
-  assert(ScavengedReg == 0 &&
-         "Scavenger slot is live, unable to scavenge another register!");
+  // Find an available scavenging slot.
+  int SI;
+  for (SI = 0; SI < Scavenged.size(); ++SI)
+    if (Scavenged[SI].Reg == 0)
+      break;
+
+  assert(SI < Scavenged.size() &&
+         "Scavenger slots are live, unable to scavenge another register!");
 
   // Avoid infinite regress
-  ScavengedReg = SReg;
+  Scavenged[SI].Reg = SReg;
 
   // If the target knows how to save/restore the register, let it do so;
   // otherwise, use the emergency stack spill slot.
   if (!TRI->saveScavengerRegister(*MBB, I, UseMI, RC, SReg)) {
     // Spill the scavenged register before I.
-    assert(ScavengingFrameIndex >= 0 &&
+    assert(Scavenged[SI].FrameIndex >= 0 &&
            "Cannot scavenge register without an emergency spill slot!");
-    TII->storeRegToStackSlot(*MBB, I, SReg, true, ScavengingFrameIndex, RC,TRI);
+    TII->storeRegToStackSlot(*MBB, I, SReg, true, Scavenged[SI].FrameIndex,
+                             RC, TRI);
     MachineBasicBlock::iterator II = prior(I);
 
     unsigned FIOperandNum = getFrameIndexOperandNum(II);
     TRI->eliminateFrameIndex(II, SPAdj, FIOperandNum, this);
 
     // Restore the scavenged register before its use (or first terminator).
-    TII->loadRegFromStackSlot(*MBB, UseMI, SReg, ScavengingFrameIndex, RC, TRI);
+    TII->loadRegFromStackSlot(*MBB, UseMI, SReg, Scavenged[SI].FrameIndex,
+                              RC, TRI);
     II = prior(UseMI);
 
     FIOperandNum = getFrameIndexOperandNum(II);
     TRI->eliminateFrameIndex(II, SPAdj, FIOperandNum, this);
   }
 
-  ScavengeRestore = prior(UseMI);
+  Scavenged[SI].Restore = prior(UseMI);
 
   // Doing this here leads to infinite regress.
-  // ScavengedReg = SReg;
+  // Scavenged[SI].Reg = SReg;
 
   DEBUG(dbgs() << "Scavenged register (with spill): " << TRI->getName(SReg) <<
         "\n");

diff --git a/lib/Target/AArch64/AArch64FrameLowering.cpp b/lib/Target/AArch64/AArch64FrameLowering.cpp
index 572617cc07815f632234fb77ad3fc0877568510c..dc41f2f6052525a421bc0a5a60f3e8fba82c9b5b 100644 (file)
--- a/lib/Target/AArch64/AArch64FrameLowering.cpp
+++ b/lib/Target/AArch64/AArch64FrameLowering.cpp
@@ -396,7 +396,7 @@ AArch64FrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
     // helpfully places it near either SP or FP for us to avoid
     // infinitely-regression during scavenging.
     const TargetRegisterClass *RC = &AArch64::GPR64RegClass;
-    RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+    RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                        RC->getAlignment(),
                                                        false));
   }

diff --git a/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
index abdd25174339668a41497821268a1695f4dceba0..b6b27f849a23273c427919af88a6d3be9b2debce 100644 (file)
--- a/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -680,7 +680,7 @@ ARMBaseRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // means the stack pointer cannot be used to access the emergency spill slot
   // when !hasReservedCallFrame().
 #ifndef NDEBUG
-  if (RS && FrameReg == ARM::SP && FrameIndex == RS->getScavengingFrameIndex()){
+  if (RS && FrameReg == ARM::SP && RS->isScavengingFrameIndex(FrameIndex)){
     assert(TFI->hasReservedCallFrame(MF) &&
            "Cannot use SP to access the emergency spill slot in "
            "functions without a reserved call frame");

diff --git a/lib/Target/ARM/ARMFrameLowering.cpp b/lib/Target/ARM/ARMFrameLowering.cpp
index 3b124087683ef99a5d61067c0d21e4431c0825b2..7a02adf2463381e5f3b99febf79ec43e27d1076a 100644 (file)
--- a/lib/Target/ARM/ARMFrameLowering.cpp
+++ b/lib/Target/ARM/ARMFrameLowering.cpp
@@ -1368,7 +1368,7 @@ ARMFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
         // note: Thumb1 functions spill to R12, not the stack.  Reserve a slot
         // closest to SP or frame pointer.
         const TargetRegisterClass *RC = &ARM::GPRRegClass;
-        RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+        RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                            RC->getAlignment(),
                                                            false));
       }

diff --git a/lib/Target/ARM/Thumb1RegisterInfo.cpp b/lib/Target/ARM/Thumb1RegisterInfo.cpp
index 609d502aa50ebb715ac38321e7a6efa601abb281..7452fb776ebdeba8559cf4d7ebbe0c34ecaaf94d 100644 (file)
--- a/lib/Target/ARM/Thumb1RegisterInfo.cpp
+++ b/lib/Target/ARM/Thumb1RegisterInfo.cpp
@@ -588,7 +588,7 @@ Thumb1RegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   // means the stack pointer cannot be used to access the emergency spill slot
   // when !hasReservedCallFrame().
 #ifndef NDEBUG
-  if (RS && FrameReg == ARM::SP && FrameIndex == RS->getScavengingFrameIndex()){
+  if (RS && FrameReg == ARM::SP && RS->isScavengingFrameIndex(FrameIndex)){
     assert(MF.getTarget().getFrameLowering()->hasReservedCallFrame(MF) &&
            "Cannot use SP to access the emergency spill slot in "
            "functions without a reserved call frame");

diff --git a/lib/Target/Mips/MipsSEFrameLowering.cpp b/lib/Target/Mips/MipsSEFrameLowering.cpp
index 0dd671376f8e38498ab61f6bd51715c1b7112bca..c67e1adef6037db35b594f202efdca16f1a86e46 100644 (file)
--- a/lib/Target/Mips/MipsSEFrameLowering.cpp
+++ b/lib/Target/Mips/MipsSEFrameLowering.cpp
@@ -295,7 +295,7 @@ processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
     &Mips::CPU64RegsRegClass : &Mips::CPURegsRegClass;
   int FI = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
                                                 RC->getAlignment(), false);
-  RS->setScavengingFrameIndex(FI);
+  RS->addScavengingFrameIndex(FI);
 }
 
 const MipsFrameLowering *

diff --git a/lib/Target/PowerPC/PPCFrameLowering.cpp b/lib/Target/PowerPC/PPCFrameLowering.cpp
index 0108f7256e2d849c5cab0fe131665900e9099aa2..707c2a5d2638493d67a5c5492cd8760712a24838 100644 (file)
--- a/lib/Target/PowerPC/PPCFrameLowering.cpp
+++ b/lib/Target/PowerPC/PPCFrameLowering.cpp
@@ -1086,7 +1086,7 @@ PPCFrameLowering::addScavengingSpillSlot(MachineFunction &MF,
     const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
     const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
     const TargetRegisterClass *RC = Subtarget.isPPC64() ? G8RC : GPRC;
-    RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+    RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                        RC->getAlignment(),
                                                        false));
   }

diff --git a/lib/Target/XCore/XCoreFrameLowering.cpp b/lib/Target/XCore/XCoreFrameLowering.cpp
index 019c4570d93d9e392b1da759b516b7bdae4c3650..6b6480e4b46127b386c51df6c88a2cc50e73a878 100644 (file)
--- a/lib/Target/XCore/XCoreFrameLowering.cpp
+++ b/lib/Target/XCore/XCoreFrameLowering.cpp
@@ -409,7 +409,7 @@ XCoreFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   }
   if (RegInfo->requiresRegisterScavenging(MF)) {
     // Reserve a slot close to SP or frame pointer.
-    RS->setScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+    RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                        RC->getAlignment(),
                                                        false));
   }