[mips] Stop reserving register AT and use register scavenger when a scratch

register is needed.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@167341 91177308-0d34-0410-b5e6-96231b3b80d8

5 files changed, 47 insertions, 13 deletions

diff --git a/lib/Target/Mips/MipsRegisterInfo.cpp b/lib/Target/Mips/MipsRegisterInfo.cpp
index 8917820251..d8e0dd436a 100644
--- a/lib/Target/Mips/MipsRegisterInfo.cpp
+++ b/lib/Target/Mips/MipsRegisterInfo.cpp
@@ -81,11 +81,11 @@ MipsRegisterInfo::getCallPreservedMask(CallingConv::ID) const {
 BitVector MipsRegisterInfo::
 getReservedRegs(const MachineFunction &MF) const {
   static const uint16_t ReservedCPURegs[] = {
-    Mips::ZERO, Mips::AT, Mips::K0, Mips::K1, Mips::SP
+    Mips::ZERO, Mips::K0, Mips::K1, Mips::SP
   };
 
   static const uint16_t ReservedCPU64Regs[] = {
-    Mips::ZERO_64, Mips::AT_64, Mips::K0_64, Mips::K1_64, Mips::SP_64
+    Mips::ZERO_64, Mips::K0_64, Mips::K1_64, Mips::SP_64
   };
 
   BitVector Reserved(getNumRegs());
diff --git a/lib/Target/Mips/MipsSEFrameLowering.cpp b/lib/Target/Mips/MipsSEFrameLowering.cpp
index 16a6757d66..03f5176b29 100644
--- a/lib/Target/Mips/MipsSEFrameLowering.cpp
+++ b/lib/Target/Mips/MipsSEFrameLowering.cpp
@@ -22,6 +22,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/RegisterScavenging.h"
 #include "llvm/DataLayout.h"
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/Support/CommandLine.h"
@@ -202,6 +203,19 @@ processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
   // Mark $fp as used if function has dedicated frame pointer.
   if (hasFP(MF))
     MRI.setPhysRegUsed(FP);
+
+  // Set scavenging frame index if necessary.
+  uint64_t MaxSPOffset = MF.getInfo<MipsFunctionInfo>()->getIncomingArgSize() +
+    estimateStackSize(MF);
+
+  if (isInt<16>(MaxSPOffset))
+    return;
+
+  const TargetRegisterClass *RC = STI.isABI_N64() ?
+    &Mips::CPU64RegsRegClass : &Mips::CPURegsRegClass;
+  int FI = MF.getFrameInfo()->CreateStackObject(RC->getSize(),
+                                                RC->getAlignment(), false);
+  RS->setScavengingFrameIndex(FI);
 }
 
 const MipsFrameLowering *
diff --git a/lib/Target/Mips/MipsSEInstrInfo.cpp b/lib/Target/Mips/MipsSEInstrInfo.cpp
index 818af0319a..fb0f9df038 100644
--- a/lib/Target/Mips/MipsSEInstrInfo.cpp
+++ b/lib/Target/Mips/MipsSEInstrInfo.cpp
@@ -261,7 +261,7 @@ void MipsSEInstrInfo::adjustStackPtr(unsigned SP, int64_t Amount,
     BuildMI(MBB, I, DL, get(ADDiu), SP).addReg(SP).addImm(Amount);
   else { // Expand immediate that doesn't fit in 16-bit.
     unsigned Reg = loadImmediate(Amount, MBB, I, DL, 0);
-    BuildMI(MBB, I, DL, get(ADDu), SP).addReg(SP).addReg(Reg);
+    BuildMI(MBB, I, DL, get(ADDu), SP).addReg(SP).addReg(Reg, RegState::Kill);
   }
 }
 
@@ -273,10 +273,12 @@ MipsSEInstrInfo::loadImmediate(int64_t Imm, MachineBasicBlock &MBB,
                                unsigned *NewImm) const {
   MipsAnalyzeImmediate AnalyzeImm;
   const MipsSubtarget &STI = TM.getSubtarget<MipsSubtarget>();
+  MachineRegisterInfo &RegInfo = MBB.getParent()->getRegInfo();
   unsigned Size = STI.isABI_N64() ? 64 : 32;
   unsigned LUi = STI.isABI_N64() ? Mips::LUi64 : Mips::LUi;
   unsigned ZEROReg = STI.isABI_N64() ? Mips::ZERO_64 : Mips::ZERO;
-  unsigned ATReg = STI.isABI_N64() ? Mips::AT_64 : Mips::AT;
+  const TargetRegisterClass *RC = STI.isABI_N64() ?
+    &Mips::CPU64RegsRegClass : &Mips::CPURegsRegClass;
   bool LastInstrIsADDiu = NewImm;
 
   const MipsAnalyzeImmediate::InstSeq &Seq =
@@ -288,22 +290,23 @@ MipsSEInstrInfo::loadImmediate(int64_t Imm, MachineBasicBlock &MBB,
   // The first instruction can be a LUi, which is different from other
   // instructions (ADDiu, ORI and SLL) in that it does not have a register
   // operand.
+  unsigned Reg = RegInfo.createVirtualRegister(RC);
+
   if (Inst->Opc == LUi)
-    BuildMI(MBB, II, DL, get(LUi), ATReg)
-      .addImm(SignExtend64<16>(Inst->ImmOpnd));
+    BuildMI(MBB, II, DL, get(LUi), Reg).addImm(SignExtend64<16>(Inst->ImmOpnd));
   else
-    BuildMI(MBB, II, DL, get(Inst->Opc), ATReg).addReg(ZEROReg)
+    BuildMI(MBB, II, DL, get(Inst->Opc), Reg).addReg(ZEROReg)
       .addImm(SignExtend64<16>(Inst->ImmOpnd));
 
   // Build the remaining instructions in Seq.
   for (++Inst; Inst != Seq.end() - LastInstrIsADDiu; ++Inst)
-    BuildMI(MBB, II, DL, get(Inst->Opc), ATReg).addReg(ATReg)
+    BuildMI(MBB, II, DL, get(Inst->Opc), Reg).addReg(Reg, RegState::Kill)
       .addImm(SignExtend64<16>(Inst->ImmOpnd));
 
   if (LastInstrIsADDiu)
     *NewImm = Inst->ImmOpnd;
 
-  return ATReg;
+  return Reg;
 }
 
 unsigned MipsSEInstrInfo::GetAnalyzableBrOpc(unsigned Opc) const {
diff --git a/lib/Target/Mips/MipsSERegisterInfo.cpp b/lib/Target/Mips/MipsSERegisterInfo.cpp
index b35d05c563..56b9ba95e5 100644
--- a/lib/Target/Mips/MipsSERegisterInfo.cpp
+++ b/lib/Target/Mips/MipsSERegisterInfo.cpp
@@ -26,6 +26,7 @@
 #include "llvm/CodeGen/MachineInstrBuilder.h"
 #include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
 #include "llvm/Target/TargetFrameLowering.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetOptions.h"
@@ -43,6 +44,16 @@ MipsSERegisterInfo::MipsSERegisterInfo(const MipsSubtarget &ST,
                                        const MipsSEInstrInfo &I)
   : MipsRegisterInfo(ST), TII(I) {}
 
+bool MipsSERegisterInfo::
+requiresRegisterScavenging(const MachineFunction &MF) const {
+  return true;
+}
+
+bool MipsSERegisterInfo::
+requiresFrameIndexScavenging(const MachineFunction &MF) const {
+  return true;
+}
+
 // This function eliminate ADJCALLSTACKDOWN,
 // ADJCALLSTACKUP pseudo instructions
 void MipsSERegisterInfo::
@@ -102,6 +113,7 @@ void MipsSERegisterInfo::eliminateFI(MachineBasicBlock::iterator II,
   // - If the frame object is any of the following, its offset must be adjusted
   //   by adding the size of the stack:
   //   incoming argument, callee-saved register location or local variable.
+  bool IsKill = false;
   int64_t Offset;
 
   Offset = SPOffset + (int64_t)StackSize;
@@ -115,16 +127,17 @@ void MipsSERegisterInfo::eliminateFI(MachineBasicBlock::iterator II,
     MachineBasicBlock &MBB = *MI.getParent();
     DebugLoc DL = II->getDebugLoc();
     unsigned ADDu = Subtarget.isABI_N64() ? Mips::DADDu : Mips::ADDu;
-    unsigned ATReg = Subtarget.isABI_N64() ? Mips::AT_64 : Mips::AT;
     unsigned NewImm;
 
     unsigned Reg = TII.loadImmediate(Offset, MBB, II, DL, &NewImm);
-    BuildMI(MBB, II, DL, TII.get(ADDu), ATReg).addReg(FrameReg).addReg(Reg);
+    BuildMI(MBB, II, DL, TII.get(ADDu), Reg).addReg(FrameReg)
+      .addReg(Reg, RegState::Kill);
 
-    FrameReg = ATReg;
+    FrameReg = Reg;
     Offset = SignExtend64<16>(NewImm);
+    IsKill = true;
   }
 
-  MI.getOperand(OpNo).ChangeToRegister(FrameReg, false);
+  MI.getOperand(OpNo).ChangeToRegister(FrameReg, false, false, IsKill);
   MI.getOperand(OpNo + 1).ChangeToImmediate(Offset);
 }
diff --git a/lib/Target/Mips/MipsSERegisterInfo.h b/lib/Target/Mips/MipsSERegisterInfo.h
index b4eab65522..7437bd36c3 100644
--- a/lib/Target/Mips/MipsSERegisterInfo.h
+++ b/lib/Target/Mips/MipsSERegisterInfo.h
@@ -27,6 +27,10 @@ public:
   MipsSERegisterInfo(const MipsSubtarget &Subtarget,
                      const MipsSEInstrInfo &TII);
 
+  bool requiresRegisterScavenging(const MachineFunction &MF) const;
+
+  bool requiresFrameIndexScavenging(const MachineFunction &MF) const;
+
   void eliminateCallFramePseudoInstr(MachineFunction &MF,
                                      MachineBasicBlock &MBB,
                                      MachineBasicBlock::iterator I) const;