[llvm-commits] [llvm] r39763 - /llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp
Bruno Cardoso Lopes
bruno.cardoso at gmail.com
Wed Jul 11 16:21:31 PDT 2007
Author: bruno
Date: Wed Jul 11 18:21:31 2007
New Revision: 39763
URL: http://llvm.org/viewvc/llvm-project?rev=39763&view=rev
Log:
Added support for framepointer
Prologue/Epilogue support fp,ra save/restore and use the stack frame the right
way!
Modified:
llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp
Modified: llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp?rev=39763&r1=39762&r2=39763&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp (original)
+++ llvm/trunk/lib/Target/Mips/MipsRegisterInfo.cpp Wed Jul 11 18:21:31 2007
@@ -15,6 +15,7 @@
#include "Mips.h"
#include "MipsRegisterInfo.h"
+#include "MipsMachineFunction.h"
#include "llvm/Constants.h"
#include "llvm/Type.h"
#include "llvm/Function.h"
@@ -46,8 +47,8 @@
const TargetRegisterClass *RC) const
{
if (RC == Mips::CPURegsRegisterClass)
- BuildMI(MBB, I, TII.get(Mips::SW)).addFrameIndex(FI)
- .addImm(0).addReg(SrcReg, false, false, true);
+ BuildMI(MBB, I, TII.get(Mips::SW)).addReg(SrcReg, false, false, true)
+ .addImm(0).addFrameIndex(FI);
else
assert(0 && "Can't store this register to stack slot");
}
@@ -154,13 +155,62 @@
}
//===----------------------------------------------------------------------===//
+//
// Stack Frame Processing methods
+// +----------------------------+
+//
+// Too meet ABI, we construct the frame on the reverse
+// of natural order.
+//
+// The LLVM Frame will look like this:
+//
+// As the stack grows down, we start at 0, and the reference
+// is decrement.
+//
+// 0 ----------
+// -4 Args to pass
+// . saved "Callee Saved" Registers
+// . Local Area
+// . saved FP
+// . saved RA
+// -StackSize -----------
+//
+// On the EliminateFrameIndex we just negate the address above
+// and we get the stack frame required by the ABI, which is:
+//
+// sp + stacksize -------------
+// saved $RA (only on non-leaf functions)
+// saved $FP (only with frame pointer)
+// saved "Callee Saved" Registers
+// Local Area
+// saved $GP (used in PIC - not supported yet)
+// Args to pass area
+// sp -------------
+//
+// The sp is the stack pointer subtracted/added from the stack size
+// at the Prologue/Epilogue
+//
+// References to the previous stack (to obtain arguments) are done
+// with fixed location stack frames using positive stack offsets.
+//
+// Examples:
+// - reference to the actual stack frame
+// for any local area var there is smt like : FI >= 0, StackOffset: -4
+// sw REGX, 4(REGY)
+//
+// - reference to previous stack frame
+// suppose there's a store to the 5th arguments : FI < 0, StackOffset: 16.
+// The emitted instruction will be something like:
+// sw REGX, 16+StackSize (REGY)
+//
//===----------------------------------------------------------------------===//
-// True if target has frame pointer
+// 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 MipsRegisterInfo::
hasFP(const MachineFunction &MF) const {
- return false;
+ return (NoFramePointerElim || MF.getFrameInfo()->hasVarSizedObjects());
}
// This function eliminate ADJCALLSTACKDOWN,
@@ -179,35 +229,30 @@
eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
RegScavenger *RS) const
{
- unsigned i = 0;
MachineInstr &MI = *II;
MachineFunction &MF = *MI.getParent()->getParent();
+ unsigned i = 0;
while (!MI.getOperand(i).isFrameIndex()) {
++i;
assert(i < MI.getNumOperands() &&
"Instr doesn't have FrameIndex operand!");
}
- // FrameInfo addressable stack objects are accessed
- // using neg. offsets, so we must add with the stack
- // size to obtain $sp relative address.
int FrameIndex = MI.getOperand(i).getFrameIndex();
int stackSize = MF.getFrameInfo()->getStackSize();
int spOffset = MF.getFrameInfo()->getObjectOffset(FrameIndex);
#ifndef NDEBUG
- DOUT << "\n<--------->\n";
+ DOUT << "\nFunction : " << MF.getFunction()->getName() << "\n";
+ DOUT << "<--------->\n";
MI.print(DOUT);
DOUT << "FrameIndex : " << FrameIndex << "\n";
DOUT << "spOffset : " << spOffset << "\n";
DOUT << "stackSize : " << stackSize << "\n";
#endif
- // If the FrameIndex points to a positive SPOffset this
- // means we are inside the callee and getting the arguments
- // from the caller stack
- int Offset = (-(stackSize)) + spOffset;
+ int Offset = ( (spOffset >= 0) ? (stackSize + spOffset) : (-spOffset));
#ifndef NDEBUG
DOUT << "Offset : " << Offset << "\n";
@@ -215,51 +260,141 @@
#endif
MI.getOperand(i-1).ChangeToImmediate(Offset);
- MI.getOperand(i).ChangeToRegister(Mips::SP,false);
+ MI.getOperand(i).ChangeToRegister(getFrameRegister(MF),false);
}
void MipsRegisterInfo::
emitPrologue(MachineFunction &MF) const
{
- MachineBasicBlock &MBB = MF.front();
- MachineFrameInfo *MFI = MF.getFrameInfo();
+ MachineBasicBlock &MBB = MF.front();
+ MachineFrameInfo *MFI = MF.getFrameInfo();
+ MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
+ MachineBasicBlock::iterator MBBI = MBB.begin();
// Get the number of bytes to allocate from the FrameInfo
int NumBytes = (int) MFI->getStackSize();
+ #ifndef NDEBUG
+ DOUT << "\n<--- EMIT PROLOGUE --->";
+ DOUT << "Stack size :" << NumBytes << "\n";
+ #endif
+
// Do we need to allocate space on the stack?
if (NumBytes == 0) return;
- // FIXME: is Stack Align needed here ?? (maybe it's done before...)
+ int FPOffset, RAOffset;
+
+ // Always allocate space for saved RA and FP,
+ // even if FramePointer is not used. When not
+ // using FP, the last stack slot becomes empty
+ // and RA is saved before it.
+ if ((hasFP(MF)) && (MFI->hasCalls())) {
+ FPOffset = NumBytes;
+ RAOffset = (NumBytes+4);
+ } else if ((!hasFP(MF)) && (MFI->hasCalls())) {
+ FPOffset = 0;
+ RAOffset = NumBytes;
+ } else if ((hasFP(MF)) && (!MFI->hasCalls())) {
+ FPOffset = NumBytes;
+ RAOffset = 0;
+ }
+
+ MFI->setObjectOffset(MFI->CreateStackObject(4,4), -FPOffset);
+ MFI->setObjectOffset(MFI->CreateStackObject(4,4), -RAOffset);
+ MipsFI->setFPStackOffset(FPOffset);
+ MipsFI->setRAStackOffset(RAOffset);
+
+ #ifndef NDEBUG
+ DOUT << "FPOffset :" << FPOffset << "\n";
+ DOUT << "RAOffset :" << RAOffset << "\n";
+ #endif
+
+ // Align stack.
+ NumBytes += 8;
unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
- NumBytes = -((NumBytes+Align-1)/Align*Align);
+ NumBytes = ((NumBytes+Align-1)/Align*Align);
- // Update frame info to pretend that this is part of the stack...
+ #ifndef NDEBUG
+ DOUT << "New stack size :" << NumBytes << "\n\n";
+ #endif
+
+ // Update frame info
MFI->setStackSize(NumBytes);
- // adjust stack : addi sp, sp, (-imm)
- BuildMI(MBB, MBB.begin(), TII.get(Mips::ADDi), Mips::SP)
- .addReg(Mips::SP).addImm(NumBytes);
+ // Adjust stack : addi sp, sp, (-imm)
+ BuildMI(MBB, MBBI, TII.get(Mips::ADDiu), Mips::SP)
+ .addReg(Mips::SP).addImm(-NumBytes);
+
+ // Save the return address only if the function isnt a leaf one.
+ // sw $ra, stack_loc($sp)
+ if (MFI->hasCalls()) {
+ BuildMI(MBB, MBBI, TII.get(Mips::SW))
+ .addReg(Mips::RA).addImm(RAOffset).addReg(Mips::SP);
+ }
+
+ // if framepointer enabled, save it and set it
+ // to point to the stack pointer
+ if (hasFP(MF)) {
+ // sw $fp,stack_loc($sp)
+ BuildMI(MBB, MBBI, TII.get(Mips::SW))
+ .addReg(Mips::FP).addImm(FPOffset).addReg(Mips::SP);
+
+ // move $fp, $sp
+ BuildMI(MBB, MBBI, TII.get(Mips::ADDu), Mips::FP)
+ .addReg(Mips::SP).addReg(Mips::ZERO);
+ }
}
void MipsRegisterInfo::
emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const
{
MachineBasicBlock::iterator MBBI = prior(MBB.end());
- MachineFrameInfo *MFI = MF.getFrameInfo();
+ MachineFrameInfo *MFI = MF.getFrameInfo();
+ MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
// Get the number of bytes from FrameInfo
int NumBytes = (int) MFI->getStackSize();
+ // Get the FI's where RA and FP are saved.
+ int FPOffset = MipsFI->getFPStackOffset();
+ int RAOffset = MipsFI->getRAStackOffset();
+
+ #ifndef NDEBUG
+ DOUT << "\n<--- EMIT EPILOGUE --->" << "\n";
+ DOUT << "Stack size :" << NumBytes << "\n";
+ DOUT << "FPOffset :" << FPOffset << "\n";
+ DOUT << "RAOffset :" << RAOffset << "\n\n";
+ #endif
+
+ // if framepointer enabled, restore it and restore the
+ // stack pointer
+ if (hasFP(MF)) {
+ // move $sp, $fp
+ BuildMI(MBB, MBBI, TII.get(Mips::ADDu), Mips::SP)
+ .addReg(Mips::FP).addReg(Mips::ZERO);
+
+ // lw $fp,stack_loc($sp)
+ BuildMI(MBB, MBBI, TII.get(Mips::LW))
+ .addReg(Mips::FP).addImm(FPOffset).addReg(Mips::SP);
+ }
+
+ // Restore the return address only if the function isnt a leaf one.
+ // lw $ra, stack_loc($sp)
+ if (MFI->hasCalls()) {
+ BuildMI(MBB, MBBI, TII.get(Mips::LW))
+ .addReg(Mips::RA).addImm(RAOffset).addReg(Mips::SP);
+ }
+
// adjust stack : insert addi sp, sp, (imm)
if (NumBytes) {
- BuildMI(MBB, MBBI, TII.get(Mips::ADDi), Mips::SP)
- .addReg(Mips::SP).addImm(-NumBytes);
+ BuildMI(MBB, MBBI, TII.get(Mips::ADDiu), Mips::SP)
+ .addReg(Mips::SP).addImm(NumBytes);
}
}
void MipsRegisterInfo::
-processFunctionBeforeFrameFinalized(MachineFunction &MF) const {}
+processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
+}
unsigned MipsRegisterInfo::
getRARegister() const {
@@ -268,8 +403,7 @@
unsigned MipsRegisterInfo::
getFrameRegister(MachineFunction &MF) const {
- assert(0 && "What is the frame register");
- return Mips::FP;
+ return hasFP(MF) ? Mips::FP : Mips::SP;
}
unsigned MipsRegisterInfo::
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