1 files changed, 148 insertions, 26 deletions

diff --git a/lib/Target/Sparc/SparcFrameLowering.cpp b/lib/Target/Sparc/SparcFrameLowering.cpp
index a0dae6e..536e466 100644
--- a/lib/Target/Sparc/SparcFrameLowering.cpp
+++ b/lib/Target/Sparc/SparcFrameLowering.cpp
@@ -26,7 +26,16 @@
 
 using namespace llvm;
 
+static cl::opt<bool>
+DisableLeafProc("disable-sparc-leaf-proc",
+                cl::init(false),
+                cl::desc("Disable Sparc leaf procedure optimization."),
+                cl::Hidden);
+
+
 void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
+  SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
+
   MachineBasicBlock &MBB = MF.front();
   MachineFrameInfo *MFI = MF.getFrameInfo();
   const SparcInstrInfo &TII =
@@ -37,22 +46,18 @@ void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
   // Get the number of bytes to allocate from the FrameInfo
   int NumBytes = (int) MFI->getStackSize();
 
-  // Emit the correct save instruction based on the number of bytes in
-  // the frame. Minimum stack frame size according to V8 ABI is:
-  //   16 words for register window spill
-  //    1 word for address of returned aggregate-value
-  // +  6 words for passing parameters on the stack
-  // ----------
-  //   23 words * 4 bytes per word = 92 bytes
-  NumBytes += 92;
-
-  // Round up to next doubleword boundary -- a double-word boundary
-  // is required by the ABI.
-  NumBytes = (NumBytes + 7) & ~7;
-  NumBytes = -NumBytes;
+  unsigned SAVEri = SP::SAVEri;
+  unsigned SAVErr = SP::SAVErr;
+  if (FuncInfo->isLeafProc()) {
+    if (NumBytes == 0)
+      return;
+    SAVEri = SP::ADDri;
+    SAVErr = SP::ADDrr;
+  }
+  NumBytes = - SubTarget.getAdjustedFrameSize(NumBytes);
 
   if (NumBytes >= -4096) {
-    BuildMI(MBB, MBBI, dl, TII.get(SP::SAVEri), SP::O6)
+    BuildMI(MBB, MBBI, dl, TII.get(SAVEri), SP::O6)
       .addReg(SP::O6).addImm(NumBytes);
   } else {
     // Emit this the hard way.  This clobbers G1 which we always know is
@@ -62,7 +67,7 @@ void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
     // Emit G1 = G1 + I6
     BuildMI(MBB, MBBI, dl, TII.get(SP::ORri), SP::G1)
       .addReg(SP::G1).addImm(NumBytes & ((1 << 10)-1));
-    BuildMI(MBB, MBBI, dl, TII.get(SP::SAVErr), SP::O6)
+    BuildMI(MBB, MBBI, dl, TII.get(SAVErr), SP::O6)
       .addReg(SP::O6).addReg(SP::G1);
   }
 }
@@ -70,27 +75,144 @@ void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
 void SparcFrameLowering::
 eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                               MachineBasicBlock::iterator I) const {
-  MachineInstr &MI = *I;
-  DebugLoc dl = MI.getDebugLoc();
-  int Size = MI.getOperand(0).getImm();
-  if (MI.getOpcode() == SP::ADJCALLSTACKDOWN)
-    Size = -Size;
-  const SparcInstrInfo &TII =
-    *static_cast<const SparcInstrInfo*>(MF.getTarget().getInstrInfo());
-  if (Size)
-    BuildMI(MBB, I, dl, TII.get(SP::ADDri), SP::O6).addReg(SP::O6).addImm(Size);
+  if (!hasReservedCallFrame(MF)) {
+    MachineInstr &MI = *I;
+    DebugLoc DL = MI.getDebugLoc();
+    int Size = MI.getOperand(0).getImm();
+    if (MI.getOpcode() == SP::ADJCALLSTACKDOWN)
+      Size = -Size;
+    const SparcInstrInfo &TII =
+      *static_cast<const SparcInstrInfo*>(MF.getTarget().getInstrInfo());
+    if (Size)
+      BuildMI(MBB, I, DL, TII.get(SP::ADDri), SP::O6).addReg(SP::O6)
+        .addImm(Size);
+  }
   MBB.erase(I);
 }
 
 
 void SparcFrameLowering::emitEpilogue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const {
+  SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
   const SparcInstrInfo &TII =
     *static_cast<const SparcInstrInfo*>(MF.getTarget().getInstrInfo());
   DebugLoc dl = MBBI->getDebugLoc();
   assert(MBBI->getOpcode() == SP::RETL &&
          "Can only put epilog before 'retl' instruction!");
-  BuildMI(MBB, MBBI, dl, TII.get(SP::RESTORErr), SP::G0).addReg(SP::G0)
-    .addReg(SP::G0);
+  if (!FuncInfo->isLeafProc()) {
+    BuildMI(MBB, MBBI, dl, TII.get(SP::RESTORErr), SP::G0).addReg(SP::G0)
+      .addReg(SP::G0);
+    return;
+  }
+  MachineFrameInfo *MFI = MF.getFrameInfo();
+
+  int NumBytes = (int) MFI->getStackSize();
+  if (NumBytes == 0)
+    return;
+
+  NumBytes = SubTarget.getAdjustedFrameSize(NumBytes);
+
+  if (NumBytes < 4096) {
+    BuildMI(MBB, MBBI, dl, TII.get(SP::ADDri), SP::O6)
+      .addReg(SP::O6).addImm(NumBytes);
+  } else {
+    // Emit this the hard way.  This clobbers G1 which we always know is
+    // available here.
+    unsigned OffHi = (unsigned)NumBytes >> 10U;
+    BuildMI(MBB, MBBI, dl, TII.get(SP::SETHIi), SP::G1).addImm(OffHi);
+    // Emit G1 = G1 + I6
+    BuildMI(MBB, MBBI, dl, TII.get(SP::ORri), SP::G1)
+      .addReg(SP::G1).addImm(NumBytes & ((1 << 10)-1));
+    BuildMI(MBB, MBBI, dl, TII.get(SP::ADDrr), SP::O6)
+      .addReg(SP::O6).addReg(SP::G1);
+  }
+}
+
+bool SparcFrameLowering::hasReservedCallFrame(const MachineFunction &MF) const {
+  // Reserve call frame if there are no variable sized objects on the stack.
+  return !MF.getFrameInfo()->hasVarSizedObjects();
+}
+
+// hasFP - Return true if the specified function should have a dedicated frame
+// pointer register.  This is true if the function has variable sized allocas or
+// if frame pointer elimination is disabled.
+bool SparcFrameLowering::hasFP(const MachineFunction &MF) const {
+  const MachineFrameInfo *MFI = MF.getFrameInfo();
+  return MF.getTarget().Options.DisableFramePointerElim(MF) ||
+    MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
+}
+
+
+static bool LLVM_ATTRIBUTE_UNUSED verifyLeafProcRegUse(MachineRegisterInfo *MRI)
+{
+
+  for (unsigned reg = SP::I0; reg <= SP::I7; ++reg)
+    if (MRI->isPhysRegUsed(reg))
+      return false;
+
+  for (unsigned reg = SP::L0; reg <= SP::L7; ++reg)
+    if (MRI->isPhysRegUsed(reg))
+      return false;
+
+  return true;
+}
+
+bool SparcFrameLowering::isLeafProc(MachineFunction &MF) const
+{
+
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+  MachineFrameInfo    *MFI = MF.getFrameInfo();
+
+  return !(MFI->hasCalls()              // has calls
+           || MRI.isPhysRegUsed(SP::L0) // Too many registers needed
+           || MRI.isPhysRegUsed(SP::O6) // %SP is used
+           || hasFP(MF));               // need %FP
+}
+
+void SparcFrameLowering::remapRegsForLeafProc(MachineFunction &MF) const {
+
+  MachineRegisterInfo &MRI = MF.getRegInfo();
+
+  // Remap %i[0-7] to %o[0-7].
+  for (unsigned reg = SP::I0; reg <= SP::I7; ++reg) {
+    if (!MRI.isPhysRegUsed(reg))
+      continue;
+    unsigned mapped_reg = (reg - SP::I0 + SP::O0);
+    assert(!MRI.isPhysRegUsed(mapped_reg));
+
+    // Replace I register with O register.
+    MRI.replaceRegWith(reg, mapped_reg);
+
+    // Mark the reg unused.
+    MRI.setPhysRegUnused(reg);
+  }
+
+  // Rewrite MBB's Live-ins.
+  for (MachineFunction::iterator MBB = MF.begin(), E = MF.end();
+       MBB != E; ++MBB) {
+    for (unsigned reg = SP::I0; reg <= SP::I7; ++reg) {
+      if (!MBB->isLiveIn(reg))
+        continue;
+      MBB->removeLiveIn(reg);
+      MBB->addLiveIn(reg - SP::I0 + SP::O0);
+    }
+  }
+
+  assert(verifyLeafProcRegUse(&MRI));
+#ifdef XDEBUG
+  MF.verify(0, "After LeafProc Remapping");
+#endif
+}
+
+void SparcFrameLowering::processFunctionBeforeCalleeSavedScan
+                  (MachineFunction &MF, RegScavenger *RS) const {
+
+  if (!DisableLeafProc && isLeafProc(MF)) {
+    SparcMachineFunctionInfo *MFI = MF.getInfo<SparcMachineFunctionInfo>();
+    MFI->setLeafProc(true);
+
+    remapRegsForLeafProc(MF);
+  }
+
 }