1 //=====- AlphaFrameLowering.cpp - Alpha Frame Information ------*- C++ -*-====// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file contains the Alpha implementation of TargetFrameLowering class. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "AlphaFrameLowering.h" 15 #include "AlphaInstrInfo.h" 16 #include "AlphaMachineFunctionInfo.h" 17 #include "llvm/Function.h" 18 #include "llvm/CodeGen/MachineFrameInfo.h" 19 #include "llvm/CodeGen/MachineFunction.h" 20 #include "llvm/CodeGen/MachineInstrBuilder.h" 21 #include "llvm/ADT/Twine.h" 22 23 using namespace llvm; 24 25 static long getUpper16(long l) { 26 long y = l / Alpha::IMM_MULT; 27 if (l % Alpha::IMM_MULT > Alpha::IMM_HIGH) 28 ++y; 29 return y; 30 } 31 32 static long getLower16(long l) { 33 long h = getUpper16(l); 34 return l - h * Alpha::IMM_MULT; 35 } 36 37 // hasFP - Return true if the specified function should have a dedicated frame 38 // pointer register. This is true if the function has variable sized allocas or 39 // if frame pointer elimination is disabled. 40 // 41 bool AlphaFrameLowering::hasFP(const MachineFunction &MF) const { 42 const MachineFrameInfo *MFI = MF.getFrameInfo(); 43 return MFI->hasVarSizedObjects(); 44 } 45 46 void AlphaFrameLowering::emitPrologue(MachineFunction &MF) const { 47 MachineBasicBlock &MBB = MF.front(); // Prolog goes in entry BB 48 MachineBasicBlock::iterator MBBI = MBB.begin(); 49 MachineFrameInfo *MFI = MF.getFrameInfo(); 50 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); 51 52 DebugLoc dl = (MBBI != MBB.end() ? MBBI->getDebugLoc() : DebugLoc()); 53 bool FP = hasFP(MF); 54 55 // Handle GOP offset 56 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDAHg), Alpha::R29) 57 .addGlobalAddress(MF.getFunction()).addReg(Alpha::R27).addImm(++curgpdist); 58 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDAg), Alpha::R29) 59 .addGlobalAddress(MF.getFunction()).addReg(Alpha::R29).addImm(curgpdist); 60 61 BuildMI(MBB, MBBI, dl, TII.get(Alpha::ALTENT)) 62 .addGlobalAddress(MF.getFunction()); 63 64 // Get the number of bytes to allocate from the FrameInfo 65 long NumBytes = MFI->getStackSize(); 66 67 if (FP) 68 NumBytes += 8; //reserve space for the old FP 69 70 // Do we need to allocate space on the stack? 71 if (NumBytes == 0) return; 72 73 unsigned Align = getStackAlignment(); 74 NumBytes = (NumBytes+Align-1)/Align*Align; 75 76 // Update frame info to pretend that this is part of the stack... 77 MFI->setStackSize(NumBytes); 78 79 // adjust stack pointer: r30 -= numbytes 80 NumBytes = -NumBytes; 81 if (NumBytes >= Alpha::IMM_LOW) { 82 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDA), Alpha::R30).addImm(NumBytes) 83 .addReg(Alpha::R30); 84 } else if (getUpper16(NumBytes) >= Alpha::IMM_LOW) { 85 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDAH), Alpha::R30) 86 .addImm(getUpper16(NumBytes)).addReg(Alpha::R30); 87 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDA), Alpha::R30) 88 .addImm(getLower16(NumBytes)).addReg(Alpha::R30); 89 } else { 90 report_fatal_error("Too big a stack frame at " + Twine(NumBytes)); 91 } 92 93 // Now if we need to, save the old FP and set the new 94 if (FP) { 95 BuildMI(MBB, MBBI, dl, TII.get(Alpha::STQ)) 96 .addReg(Alpha::R15).addImm(0).addReg(Alpha::R30); 97 // This must be the last instr in the prolog 98 BuildMI(MBB, MBBI, dl, TII.get(Alpha::BISr), Alpha::R15) 99 .addReg(Alpha::R30).addReg(Alpha::R30); 100 } 101 102 } 103 104 void AlphaFrameLowering::emitEpilogue(MachineFunction &MF, 105 MachineBasicBlock &MBB) const { 106 const MachineFrameInfo *MFI = MF.getFrameInfo(); 107 MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr(); 108 const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo(); 109 110 assert((MBBI->getOpcode() == Alpha::RETDAG || 111 MBBI->getOpcode() == Alpha::RETDAGp) 112 && "Can only insert epilog into returning blocks"); 113 DebugLoc dl = MBBI->getDebugLoc(); 114 115 bool FP = hasFP(MF); 116 117 // Get the number of bytes allocated from the FrameInfo... 118 long NumBytes = MFI->getStackSize(); 119 120 //now if we need to, restore the old FP 121 if (FP) { 122 //copy the FP into the SP (discards allocas) 123 BuildMI(MBB, MBBI, dl, TII.get(Alpha::BISr), Alpha::R30).addReg(Alpha::R15) 124 .addReg(Alpha::R15); 125 //restore the FP 126 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDQ), Alpha::R15) 127 .addImm(0).addReg(Alpha::R15); 128 } 129 130 if (NumBytes != 0) { 131 if (NumBytes <= Alpha::IMM_HIGH) { 132 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDA), Alpha::R30).addImm(NumBytes) 133 .addReg(Alpha::R30); 134 } else if (getUpper16(NumBytes) <= Alpha::IMM_HIGH) { 135 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDAH), Alpha::R30) 136 .addImm(getUpper16(NumBytes)).addReg(Alpha::R30); 137 BuildMI(MBB, MBBI, dl, TII.get(Alpha::LDA), Alpha::R30) 138 .addImm(getLower16(NumBytes)).addReg(Alpha::R30); 139 } else { 140 report_fatal_error("Too big a stack frame at " + Twine(NumBytes)); 141 } 142 } 143 } 144
