[Sparc] Add support for leaf functions in sparc backend.

llvm-svn: 182822

Author: vegovin

llvm/lib/Target/Sparc/DelaySlotFiller.cpp

@@ -135,18 +135,22 @@ Filler::findDelayInstr(MachineBasicBlock &MBB,
   bool sawLoad = false;
   bool sawStore = false;
 
-  MachineBasicBlock::iterator I = slot;
+  if (slot == MBB.begin())
+    return MBB.end();
 
   if (slot->getOpcode() == SP::RET)
     return MBB.end();
 
   if (slot->getOpcode() == SP::RETL) {
-    --I;
-    if (I->getOpcode() != SP::RESTORErr)
-      return MBB.end();
-    //change retl to ret
-    slot->setDesc(TII->get(SP::RET));
-    return I;
+    MachineBasicBlock::iterator J = slot;
+    --J;
+
+    if (J->getOpcode() == SP::RESTORErr
+        || J->getOpcode() == SP::RESTOREri) {
+      //change retl to ret
+      slot->setDesc(TII->get(SP::RET));
+      return J;
+    }
   }
 
   //Call's delay filler can def some of call's uses.
@@ -157,6 +161,8 @@ Filler::findDelayInstr(MachineBasicBlock &MBB,
 
   bool done = false;
 
+  MachineBasicBlock::iterator I = slot;
+
   while (!done) {
     done = (I == MBB.begin());
 
@@ -274,9 +280,13 @@ void Filler::insertDefsUses(MachineBasicBlock::iterator MI,
       continue;
     if (MO.isDef())
       RegDefs.insert(Reg);
-    if (MO.isUse())
+    if (MO.isUse()) {
+      //Implicit register uses of retl are return values and
+      //retl does not use them.
+      if (MO.isImplicit() && MI->getOpcode() == SP::RETL)
+        continue;
       RegUses.insert(Reg);
-
+    }
   }
 }
 

llvm/lib/Target/Sparc/SparcFrameLowering.cpp

@@ -26,7 +26,18 @@
 
 using namespace llvm;
 
+static cl::opt<bool>
+DisableLeafProc("disable-sparc-leaf-proc",
+                cl::init(true),
+                cl::desc("Disable Sparc leaf procedure optimization."),
+                cl::Hidden);
+
+
 void SparcFrameLowering::emitPrologue(MachineFunction &MF) const {
+  SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
+  if (FuncInfo->isLeafProc())
+    return;
+
   MachineBasicBlock &MBB = MF.front();
   MachineFrameInfo *MFI = MF.getFrameInfo();
   const SparcInstrInfo &TII =
@@ -97,6 +108,9 @@ eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
 
 void SparcFrameLowering::emitEpilogue(MachineFunction &MF,
                                   MachineBasicBlock &MBB) const {
+  SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
+  if (FuncInfo->isLeafProc())
+    return;
   MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
   const SparcInstrInfo &TII =
     *static_cast<const SparcInstrInfo*>(MF.getTarget().getInstrInfo());
@@ -121,3 +135,65 @@ bool SparcFrameLowering::hasFP(const MachineFunction &MF) const {
     MFI->hasVarSizedObjects() || MFI->isFrameAddressTaken();
 }
 
+
+static bool 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);
+  }
+
+  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);
+  }
+
+}

llvm/lib/Target/Sparc/SparcFrameLowering.h

@@ -40,6 +40,15 @@ class SparcFrameLowering : public TargetFrameLowering {
 
   bool hasReservedCallFrame(const MachineFunction &MF) const;
   bool hasFP(const MachineFunction &MF) const;
+  void processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
+                                            RegScavenger *RS = NULL) const;
+
+private:
+  //Remap input registers to output registers for leaf procedure.
+  void remapRegsForLeafProc(MachineFunction &MF) const;
+
+  //Returns true if MF is a leaf procedure.
+  bool isLeafProc(MachineFunction &MF) const;
 };
 
 } // End llvm namespace

llvm/lib/Target/Sparc/SparcMachineFunctionInfo.h

@@ -28,11 +28,16 @@ namespace llvm {
     /// SRetReturnReg - Holds the virtual register into which the sret
     /// argument is passed.
     unsigned SRetReturnReg;
+
+    /// IsLeafProc - True if the function is a leaf procedure.
+    bool IsLeafProc;
   public:
     SparcMachineFunctionInfo()
-      : GlobalBaseReg(0), VarArgsFrameOffset(0), SRetReturnReg(0) {}
+      : GlobalBaseReg(0), VarArgsFrameOffset(0), SRetReturnReg(0),
+        IsLeafProc(false) {}
     explicit SparcMachineFunctionInfo(MachineFunction &MF)
-      : GlobalBaseReg(0), VarArgsFrameOffset(0), SRetReturnReg(0) {}
+      : GlobalBaseReg(0), VarArgsFrameOffset(0), SRetReturnReg(0),
+        IsLeafProc(false) {}
 
     unsigned getGlobalBaseReg() const { return GlobalBaseReg; }
     void setGlobalBaseReg(unsigned Reg) { GlobalBaseReg = Reg; }
@@ -42,6 +47,9 @@ namespace llvm {
 
     unsigned getSRetReturnReg() const { return SRetReturnReg; }
     void setSRetReturnReg(unsigned Reg) { SRetReturnReg = Reg; }
+
+    void setLeafProc(bool rhs) { IsLeafProc = rhs; }
+    bool isLeafProc() const { return IsLeafProc; }
   };
 }
 

llvm/lib/Target/Sparc/SparcRegisterInfo.cpp

@@ -13,6 +13,7 @@
 
 #include "SparcRegisterInfo.h"
 #include "Sparc.h"
+#include "SparcMachineFunctionInfo.h"
 #include "SparcSubtarget.h"
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/STLExtras.h"
@@ -89,12 +90,13 @@ SparcRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
   int64_t Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex) +
                    MI.getOperand(FIOperandNum + 1).getImm() +
                    Subtarget.getStackPointerBias();
-
+  SparcMachineFunctionInfo *FuncInfo = MF.getInfo<SparcMachineFunctionInfo>();
+  unsigned FramePtr = (FuncInfo->isLeafProc()) ? SP::O6 : SP::I6;
   // Replace frame index with a frame pointer reference.
   if (Offset >= -4096 && Offset <= 4095) {
     // If the offset is small enough to fit in the immediate field, directly
     // encode it.
-    MI.getOperand(FIOperandNum).ChangeToRegister(SP::I6, false);
+    MI.getOperand(FIOperandNum).ChangeToRegister(FramePtr, false);
     MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset);
   } else {
     // Otherwise, emit a G1 = SETHI %hi(offset).  FIXME: it would be better to 
@@ -103,7 +105,7 @@ SparcRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
     BuildMI(*MI.getParent(), II, dl, TII.get(SP::SETHIi), SP::G1).addImm(OffHi);
     // Emit G1 = G1 + I6
     BuildMI(*MI.getParent(), II, dl, TII.get(SP::ADDrr), SP::G1).addReg(SP::G1)
-      .addReg(SP::I6);
+      .addReg(FramePtr);
     // Insert: G1+%lo(offset) into the user.
     MI.getOperand(FIOperandNum).ChangeToRegister(SP::G1, false);
     MI.getOperand(FIOperandNum + 1).ChangeToImmediate(Offset & ((1 << 10)-1));

llvm/lib/Target/Sparc/SparcRegisterInfo.td

@@ -144,20 +144,10 @@ def D15 : Rd<30, "F30", [F30, F31]>, DwarfRegNum<[87]>;
 // register class for that. The i64 type is included here to allow i64 patterns
 // using the integer instructions.
 def IntRegs : RegisterClass<"SP", [i32, i64], 32,
-                            (add I0, I1, I2, I3, I4, I5,
-                                 G1,
-                                 G2, G3, G4, // OK for use only in
-                                             // applications, not libraries.
-                                 G5,         // OK for use in 64 bit mode.
-                                 L0, L1, L2, L3, L4, L5, L6, L7,
-                                 O0, O1, O2, O3, O4, O5, O7,
-                                 // Non-allocatable regs:
-                                 O6, // stack ptr
-                                 I6, // frame ptr
-                                 I7, // return address
-                                 G0, // constant zero
-                                 G6, G7 // reserved for kernel
-                                 )>;
+                            (add (sequence "I%u", 0, 7),
+                                 (sequence "G%u", 0, 7),
+                                 (sequence "L%u", 0, 7),
+                                 (sequence "O%u", 0, 7))>;
 
 // Register class for 64-bit mode, with a 64-bit spill slot size.
 // These are the same as the 32-bit registers, so TableGen will consider this

llvm/test/CodeGen/SPARC/leafproc.ll

@@ -0,0 +1,57 @@
+; RUN: llc -march=sparc -disable-sparc-leaf-proc=0 < %s | FileCheck %s
+
+; CHECK:      func_nobody:
+; CHECK:      jmp %o7+8
+; CHECK-NEXT: nop
+define void @func_nobody() {
+entry:
+  ret void
+}
+
+
+; CHECK:      return_int_const:
+; CHECK:      jmp %o7+8
+; CHECK-NEXT: or %g0, 1729, %o0
+define i32 @return_int_const() {
+entry:
+  ret i32 1729
+}
+
+; CHECK:      return_double_const:
+; CHECK:      sethi
+; CHECK:      jmp %o7+8
+; CHECK-NEXT: ldd {{.*}}, %f0
+
+define double @return_double_const() {
+entry:
+  ret double 0.000000e+00
+}
+
+; CHECK:      leaf_proc_with_args:
+; CHECK:      add {{%o[0-1]}}, {{%o[0-1]}}, [[R:%[go][0-7]]]
+; CHECK:      jmp %o7+8
+; CHECK-NEXT: add [[R]], %o2, %o0
+
+define i32 @leaf_proc_with_args(i32 %a, i32 %b, i32 %c) {
+entry:
+  %0 = add nsw i32 %b, %a
+  %1 = add nsw i32 %0, %c
+  ret i32 %1
+}
+
+; CHECK:     leaf_proc_with_args_in_stack:
+; CHECK-DAG: ld [%sp+92], {{%[go][0-7]}}
+; CHECK-DAG: ld [%sp+96], {{%[go][0-7]}}
+; CHECK:     jmp %o7+8
+; CHECK-NEXT: add {{.*}}, %o0
+define i32 @leaf_proc_with_args_in_stack(i32 %a, i32 %b, i32 %c, i32 %d, i32 %e, i32 %f, i32 %g, i32 %h) {
+entry:
+  %0 = add nsw i32 %b, %a
+  %1 = add nsw i32 %0, %c
+  %2 = add nsw i32 %1, %d
+  %3 = add nsw i32 %2, %e
+  %4 = add nsw i32 %3, %f
+  %5 = add nsw i32 %4, %g
+  %6 = add nsw i32 %5, %h
+  ret i32 %6
+}