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llvm-6502/lib/Target/PowerPC/PPCFrameLowering.cpp
Quentin Colombet 2f7322b348 [ShrinkWrap] Add (a simplified version) of shrink-wrapping. 
This patch introduces a new pass that computes the safe point to insert the
prologue and epilogue of the function.
The interest is to find safe points that are cheaper than the entry and exits
blocks.

As an example and to avoid regressions to be introduce, this patch also
implements the required bits to enable the shrink-wrapping pass for AArch64.


** Context **

Currently we insert the prologue and epilogue of the method/function in the
entry and exits blocks. Although this is correct, we can do a better job when
those are not immediately required and insert them at less frequently executed
places.
The job of the shrink-wrapping pass is to identify such places.


** Motivating example **

Let us consider the following function that perform a call only in one branch of
a if:
define i32 @f(i32 %a, i32 %b)  {
 %tmp = alloca i32, align 4
 %tmp2 = icmp slt i32 %a, %b
 br i1 %tmp2, label %true, label %false

true:
 store i32 %a, i32* %tmp, align 4
 %tmp4 = call i32 @doSomething(i32 0, i32* %tmp)
 br label %false

false:
 %tmp.0 = phi i32 [ %tmp4, %true ], [ %a, %0 ]
 ret i32 %tmp.0
}

On AArch64 this code generates (removing the cfi directives to ease
readabilities):
_f:                                     ; @f
; BB#0:
  stp x29, x30, [sp, #-16]!
  mov  x29, sp
  sub sp, sp, #16             ; =16
  cmp  w0, w1
  b.ge  LBB0_2
; BB#1:                                 ; %true
  stur  w0, [x29, #-4]
  sub x1, x29, #4             ; =4
  mov  w0, wzr
  bl  _doSomething
LBB0_2:                                 ; %false
  mov  sp, x29
  ldp x29, x30, [sp], #16
  ret

With shrink-wrapping we could generate:
_f:                                     ; @f
; BB#0:
  cmp  w0, w1
  b.ge  LBB0_2
; BB#1:                                 ; %true
  stp x29, x30, [sp, #-16]!
  mov  x29, sp
  sub sp, sp, #16             ; =16
  stur  w0, [x29, #-4]
  sub x1, x29, #4             ; =4
  mov  w0, wzr
  bl  _doSomething
  add sp, x29, #16            ; =16
  ldp x29, x30, [sp], #16
LBB0_2:                                 ; %false
  ret

Therefore, we would pay the overhead of setting up/destroying the frame only if
we actually do the call.


** Proposed Solution **

This patch introduces a new machine pass that perform the shrink-wrapping
analysis (See the comments at the beginning of ShrinkWrap.cpp for more details).
It then stores the safe save and restore point into the MachineFrameInfo
attached to the MachineFunction.
This information is then used by the PrologEpilogInserter (PEI) to place the
related code at the right place. This pass runs right before the PEI.

Unlike the original paper of Chow from PLDI’88, this implementation of
shrink-wrapping does not use expensive data-flow analysis and does not need hack
to properly avoid frequently executed point. Instead, it relies on dominance and
loop properties.

The pass is off by default and each target can opt-in by setting the
EnableShrinkWrap boolean to true in their derived class of TargetPassConfig.
This setting can also be overwritten on the command line by using
-enable-shrink-wrap.

Before you try out the pass for your target, make sure you properly fix your
emitProlog/emitEpilog/adjustForXXX method to cope with basic blocks that are not
necessarily the entry block.


** Design Decisions **

1. ShrinkWrap is its own pass right now. It could frankly be merged into PEI but
for debugging and clarity I thought it was best to have its own file.
2. Right now, we only support one save point and one restore point. At some
point we can expand this to several save point and restore point, the impacted
component would then be:
- The pass itself: New algorithm needed.
- MachineFrameInfo: Hold a list or set of Save/Restore point instead of one
  pointer.
- PEI: Should loop over the save point and restore point.
Anyhow, at least for this first iteration, I do not believe this is interesting
to support the complex cases. We should revisit that when we motivating
examples.

Differential Revision: http://reviews.llvm.org/D9210

<rdar://problem/3201744>


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@236507 91177308-0d34-0410-b5e6-96231b3b80d8
2015-05-05 17:38:16 +00:00

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//===-- PPCFrameLowering.cpp - PPC Frame Information ----------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the PPC implementation of TargetFrameLowering class.
//
//===----------------------------------------------------------------------===//
#include "PPCFrameLowering.h"
#include "PPCInstrBuilder.h"
#include "PPCInstrInfo.h"
#include "PPCMachineFunctionInfo.h"
#include "PPCSubtarget.h"
#include "PPCTargetMachine.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/IR/Function.h"
#include "llvm/Target/TargetOptions.h"
using namespace llvm;
/// VRRegNo - Map from a numbered VR register to its enum value.
///
static const uint16_t VRRegNo[] = {
PPC::V0 , PPC::V1 , PPC::V2 , PPC::V3 , PPC::V4 , PPC::V5 , PPC::V6 , PPC::V7 ,
PPC::V8 , PPC::V9 , PPC::V10, PPC::V11, PPC::V12, PPC::V13, PPC::V14, PPC::V15,
PPC::V16, PPC::V17, PPC::V18, PPC::V19, PPC::V20, PPC::V21, PPC::V22, PPC::V23,
PPC::V24, PPC::V25, PPC::V26, PPC::V27, PPC::V28, PPC::V29, PPC::V30, PPC::V31
};
static unsigned computeReturnSaveOffset(const PPCSubtarget &STI) {
if (STI.isDarwinABI())
return STI.isPPC64() ? 16 : 8;
// SVR4 ABI:
return STI.isPPC64() ? 16 : 4;
}
static unsigned computeTOCSaveOffset(const PPCSubtarget &STI) {
return STI.isELFv2ABI() ? 24 : 40;
}
static unsigned computeFramePointerSaveOffset(const PPCSubtarget &STI) {
// For the Darwin ABI:
// We cannot use the TOC save slot (offset +20) in the PowerPC linkage area
// for saving the frame pointer (if needed.) While the published ABI has
// not used this slot since at least MacOSX 10.2, there is older code
// around that does use it, and that needs to continue to work.
if (STI.isDarwinABI())
return STI.isPPC64() ? -8U : -4U;
// SVR4 ABI: First slot in the general register save area.
return STI.isPPC64() ? -8U : -4U;
}
static unsigned computeLinkageSize(const PPCSubtarget &STI) {
if (STI.isDarwinABI() || STI.isPPC64())
return (STI.isELFv2ABI() ? 4 : 6) * (STI.isPPC64() ? 8 : 4);
// SVR4 ABI:
return 8;
}
static unsigned computeBasePointerSaveOffset(const PPCSubtarget &STI) {
if (STI.isDarwinABI())
return STI.isPPC64() ? -16U : -8U;
// SVR4 ABI: First slot in the general register save area.
return STI.isPPC64()
? -16U
: (STI.getTargetMachine().getRelocationModel() == Reloc::PIC_)
? -12U
: -8U;
}
PPCFrameLowering::PPCFrameLowering(const PPCSubtarget &STI)
: TargetFrameLowering(TargetFrameLowering::StackGrowsDown,
STI.getPlatformStackAlignment(), 0),
Subtarget(STI), ReturnSaveOffset(computeReturnSaveOffset(Subtarget)),
TOCSaveOffset(computeTOCSaveOffset(Subtarget)),
FramePointerSaveOffset(computeFramePointerSaveOffset(Subtarget)),
LinkageSize(computeLinkageSize(Subtarget)),
BasePointerSaveOffset(computeBasePointerSaveOffset(STI)) {}
// With the SVR4 ABI, callee-saved registers have fixed offsets on the stack.
const PPCFrameLowering::SpillSlot *PPCFrameLowering::getCalleeSavedSpillSlots(
unsigned &NumEntries) const {
if (Subtarget.isDarwinABI()) {
NumEntries = 1;
if (Subtarget.isPPC64()) {
static const SpillSlot darwin64Offsets = {PPC::X31, -8};
return &darwin64Offsets;
} else {
static const SpillSlot darwinOffsets = {PPC::R31, -4};
return &darwinOffsets;
}
}
// Early exit if not using the SVR4 ABI.
if (!Subtarget.isSVR4ABI()) {
NumEntries = 0;
return nullptr;
}
// Note that the offsets here overlap, but this is fixed up in
// processFunctionBeforeFrameFinalized.
static const SpillSlot Offsets[] = {
// Floating-point register save area offsets.
{PPC::F31, -8},
{PPC::F30, -16},
{PPC::F29, -24},
{PPC::F28, -32},
{PPC::F27, -40},
{PPC::F26, -48},
{PPC::F25, -56},
{PPC::F24, -64},
{PPC::F23, -72},
{PPC::F22, -80},
{PPC::F21, -88},
{PPC::F20, -96},
{PPC::F19, -104},
{PPC::F18, -112},
{PPC::F17, -120},
{PPC::F16, -128},
{PPC::F15, -136},
{PPC::F14, -144},
// General register save area offsets.
{PPC::R31, -4},
{PPC::R30, -8},
{PPC::R29, -12},
{PPC::R28, -16},
{PPC::R27, -20},
{PPC::R26, -24},
{PPC::R25, -28},
{PPC::R24, -32},
{PPC::R23, -36},
{PPC::R22, -40},
{PPC::R21, -44},
{PPC::R20, -48},
{PPC::R19, -52},
{PPC::R18, -56},
{PPC::R17, -60},
{PPC::R16, -64},
{PPC::R15, -68},
{PPC::R14, -72},
// CR save area offset. We map each of the nonvolatile CR fields
// to the slot for CR2, which is the first of the nonvolatile CR
// fields to be assigned, so that we only allocate one save slot.
// See PPCRegisterInfo::hasReservedSpillSlot() for more information.
{PPC::CR2, -4},
// VRSAVE save area offset.
{PPC::VRSAVE, -4},
// Vector register save area
{PPC::V31, -16},
{PPC::V30, -32},
{PPC::V29, -48},
{PPC::V28, -64},
{PPC::V27, -80},
{PPC::V26, -96},
{PPC::V25, -112},
{PPC::V24, -128},
{PPC::V23, -144},
{PPC::V22, -160},
{PPC::V21, -176},
{PPC::V20, -192}};
static const SpillSlot Offsets64[] = {
// Floating-point register save area offsets.
{PPC::F31, -8},
{PPC::F30, -16},
{PPC::F29, -24},
{PPC::F28, -32},
{PPC::F27, -40},
{PPC::F26, -48},
{PPC::F25, -56},
{PPC::F24, -64},
{PPC::F23, -72},
{PPC::F22, -80},
{PPC::F21, -88},
{PPC::F20, -96},
{PPC::F19, -104},
{PPC::F18, -112},
{PPC::F17, -120},
{PPC::F16, -128},
{PPC::F15, -136},
{PPC::F14, -144},
// General register save area offsets.
{PPC::X31, -8},
{PPC::X30, -16},
{PPC::X29, -24},
{PPC::X28, -32},
{PPC::X27, -40},
{PPC::X26, -48},
{PPC::X25, -56},
{PPC::X24, -64},
{PPC::X23, -72},
{PPC::X22, -80},
{PPC::X21, -88},
{PPC::X20, -96},
{PPC::X19, -104},
{PPC::X18, -112},
{PPC::X17, -120},
{PPC::X16, -128},
{PPC::X15, -136},
{PPC::X14, -144},
// VRSAVE save area offset.
{PPC::VRSAVE, -4},
// Vector register save area
{PPC::V31, -16},
{PPC::V30, -32},
{PPC::V29, -48},
{PPC::V28, -64},
{PPC::V27, -80},
{PPC::V26, -96},
{PPC::V25, -112},
{PPC::V24, -128},
{PPC::V23, -144},
{PPC::V22, -160},
{PPC::V21, -176},
{PPC::V20, -192}};
if (Subtarget.isPPC64()) {
NumEntries = array_lengthof(Offsets64);
return Offsets64;
} else {
NumEntries = array_lengthof(Offsets);
return Offsets;
}
}
/// RemoveVRSaveCode - We have found that this function does not need any code
/// to manipulate the VRSAVE register, even though it uses vector registers.
/// This can happen when the only registers used are known to be live in or out
/// of the function. Remove all of the VRSAVE related code from the function.
/// FIXME: The removal of the code results in a compile failure at -O0 when the
/// function contains a function call, as the GPR containing original VRSAVE
/// contents is spilled and reloaded around the call. Without the prolog code,
/// the spill instruction refers to an undefined register. This code needs
/// to account for all uses of that GPR.
static void RemoveVRSaveCode(MachineInstr *MI) {
MachineBasicBlock *Entry = MI->getParent();
MachineFunction *MF = Entry->getParent();
// We know that the MTVRSAVE instruction immediately follows MI. Remove it.
MachineBasicBlock::iterator MBBI = MI;
++MBBI;
assert(MBBI != Entry->end() && MBBI->getOpcode() == PPC::MTVRSAVE);
MBBI->eraseFromParent();
bool RemovedAllMTVRSAVEs = true;
// See if we can find and remove the MTVRSAVE instruction from all of the
// epilog blocks.
for (MachineFunction::iterator I = MF->begin(), E = MF->end(); I != E; ++I) {
// If last instruction is a return instruction, add an epilogue
if (!I->empty() && I->back().isReturn()) {
bool FoundIt = false;
for (MBBI = I->end(); MBBI != I->begin(); ) {
--MBBI;
if (MBBI->getOpcode() == PPC::MTVRSAVE) {
MBBI->eraseFromParent(); // remove it.
FoundIt = true;
break;
}
}
RemovedAllMTVRSAVEs &= FoundIt;
}
}
// If we found and removed all MTVRSAVE instructions, remove the read of
// VRSAVE as well.
if (RemovedAllMTVRSAVEs) {
MBBI = MI;
assert(MBBI != Entry->begin() && "UPDATE_VRSAVE is first instr in block?");
--MBBI;
assert(MBBI->getOpcode() == PPC::MFVRSAVE && "VRSAVE instrs wandered?");
MBBI->eraseFromParent();
}
// Finally, nuke the UPDATE_VRSAVE.
MI->eraseFromParent();
}
// HandleVRSaveUpdate - MI is the UPDATE_VRSAVE instruction introduced by the
// instruction selector. Based on the vector registers that have been used,
// transform this into the appropriate ORI instruction.
static void HandleVRSaveUpdate(MachineInstr *MI, const TargetInstrInfo &TII) {
MachineFunction *MF = MI->getParent()->getParent();
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
DebugLoc dl = MI->getDebugLoc();
unsigned UsedRegMask = 0;
for (unsigned i = 0; i != 32; ++i)
if (MF->getRegInfo().isPhysRegUsed(VRRegNo[i]))
UsedRegMask |= 1 << (31-i);
// Live in and live out values already must be in the mask, so don't bother
// marking them.
for (MachineRegisterInfo::livein_iterator
I = MF->getRegInfo().livein_begin(),
E = MF->getRegInfo().livein_end(); I != E; ++I) {
unsigned RegNo = TRI->getEncodingValue(I->first);
if (VRRegNo[RegNo] == I->first) // If this really is a vector reg.
UsedRegMask &= ~(1 << (31-RegNo)); // Doesn't need to be marked.
}
// Live out registers appear as use operands on return instructions.
for (MachineFunction::const_iterator BI = MF->begin(), BE = MF->end();
UsedRegMask != 0 && BI != BE; ++BI) {
const MachineBasicBlock &MBB = *BI;
if (MBB.empty() || !MBB.back().isReturn())
continue;
const MachineInstr &Ret = MBB.back();
for (unsigned I = 0, E = Ret.getNumOperands(); I != E; ++I) {
const MachineOperand &MO = Ret.getOperand(I);
if (!MO.isReg() || !PPC::VRRCRegClass.contains(MO.getReg()))
continue;
unsigned RegNo = TRI->getEncodingValue(MO.getReg());
UsedRegMask &= ~(1 << (31-RegNo));
}
}
// If no registers are used, turn this into a copy.
if (UsedRegMask == 0) {
// Remove all VRSAVE code.
RemoveVRSaveCode(MI);
return;
}
unsigned SrcReg = MI->getOperand(1).getReg();
unsigned DstReg = MI->getOperand(0).getReg();
if ((UsedRegMask & 0xFFFF) == UsedRegMask) {
if (DstReg != SrcReg)
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORI), DstReg)
.addReg(SrcReg)
.addImm(UsedRegMask);
else
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORI), DstReg)
.addReg(SrcReg, RegState::Kill)
.addImm(UsedRegMask);
} else if ((UsedRegMask & 0xFFFF0000) == UsedRegMask) {
if (DstReg != SrcReg)
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORIS), DstReg)
.addReg(SrcReg)
.addImm(UsedRegMask >> 16);
else
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORIS), DstReg)
.addReg(SrcReg, RegState::Kill)
.addImm(UsedRegMask >> 16);
} else {
if (DstReg != SrcReg)
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORIS), DstReg)
.addReg(SrcReg)
.addImm(UsedRegMask >> 16);
else
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORIS), DstReg)
.addReg(SrcReg, RegState::Kill)
.addImm(UsedRegMask >> 16);
BuildMI(*MI->getParent(), MI, dl, TII.get(PPC::ORI), DstReg)
.addReg(DstReg, RegState::Kill)
.addImm(UsedRegMask & 0xFFFF);
}
// Remove the old UPDATE_VRSAVE instruction.
MI->eraseFromParent();
}
static bool spillsCR(const MachineFunction &MF) {
const PPCFunctionInfo *FuncInfo = MF.getInfo<PPCFunctionInfo>();
return FuncInfo->isCRSpilled();
}
static bool spillsVRSAVE(const MachineFunction &MF) {
const PPCFunctionInfo *FuncInfo = MF.getInfo<PPCFunctionInfo>();
return FuncInfo->isVRSAVESpilled();
}
static bool hasSpills(const MachineFunction &MF) {
const PPCFunctionInfo *FuncInfo = MF.getInfo<PPCFunctionInfo>();
return FuncInfo->hasSpills();
}
static bool hasNonRISpills(const MachineFunction &MF) {
const PPCFunctionInfo *FuncInfo = MF.getInfo<PPCFunctionInfo>();
return FuncInfo->hasNonRISpills();
}
/// MustSaveLR - Return true if this function requires that we save the LR
/// register onto the stack in the prolog and restore it in the epilog of the
/// function.
static bool MustSaveLR(const MachineFunction &MF, unsigned LR) {
const PPCFunctionInfo *MFI = MF.getInfo<PPCFunctionInfo>();
// We need a save/restore of LR if there is any def of LR (which is
// defined by calls, including the PIC setup sequence), or if there is
// some use of the LR stack slot (e.g. for builtin_return_address).
// (LR comes in 32 and 64 bit versions.)
MachineRegisterInfo::def_iterator RI = MF.getRegInfo().def_begin(LR);
return RI !=MF.getRegInfo().def_end() || MFI->isLRStoreRequired();
}
/// determineFrameLayout - Determine the size of the frame and maximum call
/// frame size.
unsigned PPCFrameLowering::determineFrameLayout(MachineFunction &MF,
bool UpdateMF,
bool UseEstimate) const {
MachineFrameInfo *MFI = MF.getFrameInfo();
// Get the number of bytes to allocate from the FrameInfo
unsigned FrameSize =
UseEstimate ? MFI->estimateStackSize(MF) : MFI->getStackSize();
// Get stack alignments. The frame must be aligned to the greatest of these:
unsigned TargetAlign = getStackAlignment(); // alignment required per the ABI
unsigned MaxAlign = MFI->getMaxAlignment(); // algmt required by data in frame
unsigned AlignMask = std::max(MaxAlign, TargetAlign) - 1;
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
// If we are a leaf function, and use up to 224 bytes of stack space,
// don't have a frame pointer, calls, or dynamic alloca then we do not need
// to adjust the stack pointer (we fit in the Red Zone).
// The 32-bit SVR4 ABI has no Red Zone. However, it can still generate
// stackless code if all local vars are reg-allocated.
bool DisableRedZone = MF.getFunction()->hasFnAttribute(Attribute::NoRedZone);
unsigned LR = RegInfo->getRARegister();
if (!DisableRedZone &&
(Subtarget.isPPC64() || // 32-bit SVR4, no stack-
!Subtarget.isSVR4ABI() || // allocated locals.
FrameSize == 0) &&
FrameSize <= 224 && // Fits in red zone.
!MFI->hasVarSizedObjects() && // No dynamic alloca.
!MFI->adjustsStack() && // No calls.
!MustSaveLR(MF, LR) &&
!RegInfo->hasBasePointer(MF)) { // No special alignment.
// No need for frame
if (UpdateMF)
MFI->setStackSize(0);
return 0;
}
// Get the maximum call frame size of all the calls.
unsigned maxCallFrameSize = MFI->getMaxCallFrameSize();
// Maximum call frame needs to be at least big enough for linkage area.
unsigned minCallFrameSize = getLinkageSize();
maxCallFrameSize = std::max(maxCallFrameSize, minCallFrameSize);
// If we have dynamic alloca then maxCallFrameSize needs to be aligned so
// that allocations will be aligned.
if (MFI->hasVarSizedObjects())
maxCallFrameSize = (maxCallFrameSize + AlignMask) & ~AlignMask;
// Update maximum call frame size.
if (UpdateMF)
MFI->setMaxCallFrameSize(maxCallFrameSize);
// Include call frame size in total.
FrameSize += maxCallFrameSize;
// Make sure the frame is aligned.
FrameSize = (FrameSize + AlignMask) & ~AlignMask;
// Update frame info.
if (UpdateMF)
MFI->setStackSize(FrameSize);
return FrameSize;
}
// hasFP - Return true if the specified function actually has a dedicated frame
// pointer register.
bool PPCFrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
// FIXME: This is pretty much broken by design: hasFP() might be called really
// early, before the stack layout was calculated and thus hasFP() might return
// true or false here depending on the time of call.
return (MFI->getStackSize()) && needsFP(MF);
}
// needsFP - 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 PPCFrameLowering::needsFP(const MachineFunction &MF) const {
const MachineFrameInfo *MFI = MF.getFrameInfo();
// Naked functions have no stack frame pushed, so we don't have a frame
// pointer.
if (MF.getFunction()->hasFnAttribute(Attribute::Naked))
return false;
return MF.getTarget().Options.DisableFramePointerElim(MF) ||
MFI->hasVarSizedObjects() ||
MFI->hasStackMap() || MFI->hasPatchPoint() ||
(MF.getTarget().Options.GuaranteedTailCallOpt &&
MF.getInfo<PPCFunctionInfo>()->hasFastCall());
}
void PPCFrameLowering::replaceFPWithRealFP(MachineFunction &MF) const {
bool is31 = needsFP(MF);
unsigned FPReg = is31 ? PPC::R31 : PPC::R1;
unsigned FP8Reg = is31 ? PPC::X31 : PPC::X1;
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
bool HasBP = RegInfo->hasBasePointer(MF);
unsigned BPReg = HasBP ? (unsigned) RegInfo->getBaseRegister(MF) : FPReg;
unsigned BP8Reg = HasBP ? (unsigned) PPC::X30 : FPReg;
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end();
BI != BE; ++BI)
for (MachineBasicBlock::iterator MBBI = BI->end(); MBBI != BI->begin(); ) {
--MBBI;
for (unsigned I = 0, E = MBBI->getNumOperands(); I != E; ++I) {
MachineOperand &MO = MBBI->getOperand(I);
if (!MO.isReg())
continue;
switch (MO.getReg()) {
case PPC::FP:
MO.setReg(FPReg);
break;
case PPC::FP8:
MO.setReg(FP8Reg);
break;
case PPC::BP:
MO.setReg(BPReg);
break;
case PPC::BP8:
MO.setReg(BP8Reg);
break;
}
}
}
}
void PPCFrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
MachineBasicBlock::iterator MBBI = MBB.begin();
MachineFrameInfo *MFI = MF.getFrameInfo();
const PPCInstrInfo &TII =
*static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
MachineModuleInfo &MMI = MF.getMMI();
const MCRegisterInfo *MRI = MMI.getContext().getRegisterInfo();
DebugLoc dl;
bool needsCFI = MMI.hasDebugInfo() ||
MF.getFunction()->needsUnwindTableEntry();
// Get processor type.
bool isPPC64 = Subtarget.isPPC64();
// Get the ABI.
bool isSVR4ABI = Subtarget.isSVR4ABI();
bool isELFv2ABI = Subtarget.isELFv2ABI();
assert((Subtarget.isDarwinABI() || isSVR4ABI) &&
"Currently only Darwin and SVR4 ABIs are supported for PowerPC.");
// Scan the prolog, looking for an UPDATE_VRSAVE instruction. If we find it,
// process it.
if (!isSVR4ABI)
for (unsigned i = 0; MBBI != MBB.end(); ++i, ++MBBI) {
if (MBBI->getOpcode() == PPC::UPDATE_VRSAVE) {
HandleVRSaveUpdate(MBBI, TII);
break;
}
}
// Move MBBI back to the beginning of the function.
MBBI = MBB.begin();
// Work out frame sizes.
unsigned FrameSize = determineFrameLayout(MF);
int NegFrameSize = -FrameSize;
if (!isInt<32>(NegFrameSize))
llvm_unreachable("Unhandled stack size!");
if (MFI->isFrameAddressTaken())
replaceFPWithRealFP(MF);
// Check if the link register (LR) must be saved.
PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
bool MustSaveLR = FI->mustSaveLR();
const SmallVectorImpl<unsigned> &MustSaveCRs = FI->getMustSaveCRs();
// Do we have a frame pointer and/or base pointer for this function?
bool HasFP = hasFP(MF);
bool HasBP = RegInfo->hasBasePointer(MF);
unsigned SPReg = isPPC64 ? PPC::X1 : PPC::R1;
unsigned BPReg = RegInfo->getBaseRegister(MF);
unsigned FPReg = isPPC64 ? PPC::X31 : PPC::R31;
unsigned LRReg = isPPC64 ? PPC::LR8 : PPC::LR;
unsigned ScratchReg = isPPC64 ? PPC::X0 : PPC::R0;
unsigned TempReg = isPPC64 ? PPC::X12 : PPC::R12; // another scratch reg
// ...(R12/X12 is volatile in both Darwin & SVR4, & can't be a function arg.)
const MCInstrDesc& MFLRInst = TII.get(isPPC64 ? PPC::MFLR8
: PPC::MFLR );
const MCInstrDesc& StoreInst = TII.get(isPPC64 ? PPC::STD
: PPC::STW );
const MCInstrDesc& StoreUpdtInst = TII.get(isPPC64 ? PPC::STDU
: PPC::STWU );
const MCInstrDesc& StoreUpdtIdxInst = TII.get(isPPC64 ? PPC::STDUX
: PPC::STWUX);
const MCInstrDesc& LoadImmShiftedInst = TII.get(isPPC64 ? PPC::LIS8
: PPC::LIS );
const MCInstrDesc& OrImmInst = TII.get(isPPC64 ? PPC::ORI8
: PPC::ORI );
const MCInstrDesc& OrInst = TII.get(isPPC64 ? PPC::OR8
: PPC::OR );
const MCInstrDesc& SubtractCarryingInst = TII.get(isPPC64 ? PPC::SUBFC8
: PPC::SUBFC);
const MCInstrDesc& SubtractImmCarryingInst = TII.get(isPPC64 ? PPC::SUBFIC8
: PPC::SUBFIC);
// Regarding this assert: Even though LR is saved in the caller's frame (i.e.,
// LROffset is positive), that slot is callee-owned. Because PPC32 SVR4 has no
// Red Zone, an asynchronous event (a form of "callee") could claim a frame &
// overwrite it, so PPC32 SVR4 must claim at least a minimal frame to save LR.
assert((isPPC64 || !isSVR4ABI || !(!FrameSize && (MustSaveLR || HasFP))) &&
"FrameSize must be >0 to save/restore the FP or LR for 32-bit SVR4.");
int LROffset = getReturnSaveOffset();
int FPOffset = 0;
if (HasFP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int FPIndex = FI->getFramePointerSaveIndex();
assert(FPIndex && "No Frame Pointer Save Slot!");
FPOffset = FFI->getObjectOffset(FPIndex);
} else {
FPOffset = getFramePointerSaveOffset();
}
}
int BPOffset = 0;
if (HasBP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int BPIndex = FI->getBasePointerSaveIndex();
assert(BPIndex && "No Base Pointer Save Slot!");
BPOffset = FFI->getObjectOffset(BPIndex);
} else {
BPOffset = getBasePointerSaveOffset();
}
}
int PBPOffset = 0;
if (FI->usesPICBase()) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int PBPIndex = FI->getPICBasePointerSaveIndex();
assert(PBPIndex && "No PIC Base Pointer Save Slot!");
PBPOffset = FFI->getObjectOffset(PBPIndex);
}
// Get stack alignments.
unsigned MaxAlign = MFI->getMaxAlignment();
if (HasBP && MaxAlign > 1)
assert(isPowerOf2_32(MaxAlign) && isInt<16>(MaxAlign) &&
"Invalid alignment!");
// Frames of 32KB & larger require special handling because they cannot be
// indexed into with a simple STDU/STWU/STD/STW immediate offset operand.
bool isLargeFrame = !isInt<16>(NegFrameSize);
if (MustSaveLR)
BuildMI(MBB, MBBI, dl, MFLRInst, ScratchReg);
assert((isPPC64 || MustSaveCRs.empty()) &&
"Prologue CR saving supported only in 64-bit mode");
if (!MustSaveCRs.empty()) { // will only occur for PPC64
// FIXME: In the ELFv2 ABI, we are not required to save all CR fields.
// If only one or two CR fields are clobbered, it could be more
// efficient to use mfocrf to selectively save just those fields.
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, dl, TII.get(PPC::MFCR8), TempReg);
for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
MIB.addReg(MustSaveCRs[i], RegState::ImplicitKill);
}
if (HasFP)
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(FPReg)
.addImm(FPOffset)
.addReg(SPReg);
if (FI->usesPICBase())
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(PPC::R30)
.addImm(PBPOffset)
.addReg(SPReg);
if (HasBP)
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(BPReg)
.addImm(BPOffset)
.addReg(SPReg);
if (MustSaveLR)
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, StoreInst)
.addReg(ScratchReg)
.addImm(LROffset)
.addReg(SPReg);
if (!MustSaveCRs.empty()) // will only occur for PPC64
BuildMI(MBB, MBBI, dl, TII.get(PPC::STW8))
.addReg(TempReg, getKillRegState(true))
.addImm(8)
.addReg(SPReg);
// Skip the rest if this is a leaf function & all spills fit in the Red Zone.
if (!FrameSize) return;
// Adjust stack pointer: r1 += NegFrameSize.
// If there is a preferred stack alignment, align R1 now
if (HasBP) {
// Save a copy of r1 as the base pointer.
BuildMI(MBB, MBBI, dl, OrInst, BPReg)
.addReg(SPReg)
.addReg(SPReg);
}
if (HasBP && MaxAlign > 1) {
if (isPPC64)
BuildMI(MBB, MBBI, dl, TII.get(PPC::RLDICL), ScratchReg)
.addReg(SPReg)
.addImm(0)
.addImm(64 - Log2_32(MaxAlign));
else // PPC32...
BuildMI(MBB, MBBI, dl, TII.get(PPC::RLWINM), ScratchReg)
.addReg(SPReg)
.addImm(0)
.addImm(32 - Log2_32(MaxAlign))
.addImm(31);
if (!isLargeFrame) {
BuildMI(MBB, MBBI, dl, SubtractImmCarryingInst, ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addImm(NegFrameSize);
} else {
BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, TempReg)
.addImm(NegFrameSize >> 16);
BuildMI(MBB, MBBI, dl, OrImmInst, TempReg)
.addReg(TempReg, RegState::Kill)
.addImm(NegFrameSize & 0xFFFF);
BuildMI(MBB, MBBI, dl, SubtractCarryingInst, ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addReg(TempReg, RegState::Kill);
}
BuildMI(MBB, MBBI, dl, StoreUpdtIdxInst, SPReg)
.addReg(SPReg, RegState::Kill)
.addReg(SPReg)
.addReg(ScratchReg);
} else if (!isLargeFrame) {
BuildMI(MBB, MBBI, dl, StoreUpdtInst, SPReg)
.addReg(SPReg)
.addImm(NegFrameSize)
.addReg(SPReg);
} else {
BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
.addImm(NegFrameSize >> 16);
BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addImm(NegFrameSize & 0xFFFF);
BuildMI(MBB, MBBI, dl, StoreUpdtIdxInst, SPReg)
.addReg(SPReg, RegState::Kill)
.addReg(SPReg)
.addReg(ScratchReg);
}
// Add Call Frame Information for the instructions we generated above.
if (needsCFI) {
unsigned CFIIndex;
if (HasBP) {
// Define CFA in terms of BP. Do this in preference to using FP/SP,
// because if the stack needed aligning then CFA won't be at a fixed
// offset from FP/SP.
unsigned Reg = MRI->getDwarfRegNum(BPReg, true);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaRegister(nullptr, Reg));
} else {
// Adjust the definition of CFA to account for the change in SP.
assert(NegFrameSize);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaOffset(nullptr, NegFrameSize));
}
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
if (HasFP) {
// Describe where FP was saved, at a fixed offset from CFA.
unsigned Reg = MRI->getDwarfRegNum(FPReg, true);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, Reg, FPOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
if (FI->usesPICBase()) {
// Describe where FP was saved, at a fixed offset from CFA.
unsigned Reg = MRI->getDwarfRegNum(PPC::R30, true);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, Reg, PBPOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
if (HasBP) {
// Describe where BP was saved, at a fixed offset from CFA.
unsigned Reg = MRI->getDwarfRegNum(BPReg, true);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, Reg, BPOffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
if (MustSaveLR) {
// Describe where LR was saved, at a fixed offset from CFA.
unsigned Reg = MRI->getDwarfRegNum(LRReg, true);
CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createOffset(nullptr, Reg, LROffset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
// If there is a frame pointer, copy R1 into R31
if (HasFP) {
BuildMI(MBB, MBBI, dl, OrInst, FPReg)
.addReg(SPReg)
.addReg(SPReg);
if (!HasBP && needsCFI) {
// Change the definition of CFA from SP+offset to FP+offset, because SP
// will change at every alloca.
unsigned Reg = MRI->getDwarfRegNum(FPReg, true);
unsigned CFIIndex = MMI.addFrameInst(
MCCFIInstruction::createDefCfaRegister(nullptr, Reg));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
if (needsCFI) {
// Describe where callee saved registers were saved, at fixed offsets from
// CFA.
const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
for (unsigned I = 0, E = CSI.size(); I != E; ++I) {
unsigned Reg = CSI[I].getReg();
if (Reg == PPC::LR || Reg == PPC::LR8 || Reg == PPC::RM) continue;
// This is a bit of a hack: CR2LT, CR2GT, CR2EQ and CR2UN are just
// subregisters of CR2. We just need to emit a move of CR2.
if (PPC::CRBITRCRegClass.contains(Reg))
continue;
// For SVR4, don't emit a move for the CR spill slot if we haven't
// spilled CRs.
if (isSVR4ABI && (PPC::CR2 <= Reg && Reg <= PPC::CR4)
&& MustSaveCRs.empty())
continue;
// For 64-bit SVR4 when we have spilled CRs, the spill location
// is SP+8, not a frame-relative slot.
if (isSVR4ABI && isPPC64 && (PPC::CR2 <= Reg && Reg <= PPC::CR4)) {
// In the ELFv1 ABI, only CR2 is noted in CFI and stands in for
// the whole CR word. In the ELFv2 ABI, every CR that was
// actually saved gets its own CFI record.
unsigned CRReg = isELFv2ABI? Reg : (unsigned) PPC::CR2;
unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(CRReg, true), 8));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
continue;
}
int Offset = MFI->getObjectOffset(CSI[I].getFrameIdx());
unsigned CFIIndex = MMI.addFrameInst(MCCFIInstruction::createOffset(
nullptr, MRI->getDwarfRegNum(Reg, true), Offset));
BuildMI(MBB, MBBI, dl, TII.get(TargetOpcode::CFI_INSTRUCTION))
.addCFIIndex(CFIIndex);
}
}
}
void PPCFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
MachineBasicBlock::iterator MBBI = MBB.getLastNonDebugInstr();
assert(MBBI != MBB.end() && "Returning block has no terminator");
const PPCInstrInfo &TII =
*static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
unsigned RetOpcode = MBBI->getOpcode();
DebugLoc dl;
assert((RetOpcode == PPC::BLR ||
RetOpcode == PPC::BLR8 ||
RetOpcode == PPC::TCRETURNri ||
RetOpcode == PPC::TCRETURNdi ||
RetOpcode == PPC::TCRETURNai ||
RetOpcode == PPC::TCRETURNri8 ||
RetOpcode == PPC::TCRETURNdi8 ||
RetOpcode == PPC::TCRETURNai8) &&
"Can only insert epilog into returning blocks");
// Get alignment info so we know how to restore the SP.
const MachineFrameInfo *MFI = MF.getFrameInfo();
// Get the number of bytes allocated from the FrameInfo.
int FrameSize = MFI->getStackSize();
// Get processor type.
bool isPPC64 = Subtarget.isPPC64();
// Get the ABI.
bool isSVR4ABI = Subtarget.isSVR4ABI();
// Check if the link register (LR) has been saved.
PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
bool MustSaveLR = FI->mustSaveLR();
const SmallVectorImpl<unsigned> &MustSaveCRs = FI->getMustSaveCRs();
// Do we have a frame pointer and/or base pointer for this function?
bool HasFP = hasFP(MF);
bool HasBP = RegInfo->hasBasePointer(MF);
unsigned SPReg = isPPC64 ? PPC::X1 : PPC::R1;
unsigned BPReg = RegInfo->getBaseRegister(MF);
unsigned FPReg = isPPC64 ? PPC::X31 : PPC::R31;
unsigned ScratchReg = isPPC64 ? PPC::X0 : PPC::R0;
unsigned TempReg = isPPC64 ? PPC::X12 : PPC::R12; // another scratch reg
const MCInstrDesc& MTLRInst = TII.get( isPPC64 ? PPC::MTLR8
: PPC::MTLR );
const MCInstrDesc& LoadInst = TII.get( isPPC64 ? PPC::LD
: PPC::LWZ );
const MCInstrDesc& LoadImmShiftedInst = TII.get( isPPC64 ? PPC::LIS8
: PPC::LIS );
const MCInstrDesc& OrImmInst = TII.get( isPPC64 ? PPC::ORI8
: PPC::ORI );
const MCInstrDesc& AddImmInst = TII.get( isPPC64 ? PPC::ADDI8
: PPC::ADDI );
const MCInstrDesc& AddInst = TII.get( isPPC64 ? PPC::ADD8
: PPC::ADD4 );
int LROffset = getReturnSaveOffset();
int FPOffset = 0;
if (HasFP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int FPIndex = FI->getFramePointerSaveIndex();
assert(FPIndex && "No Frame Pointer Save Slot!");
FPOffset = FFI->getObjectOffset(FPIndex);
} else {
FPOffset = getFramePointerSaveOffset();
}
}
int BPOffset = 0;
if (HasBP) {
if (isSVR4ABI) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int BPIndex = FI->getBasePointerSaveIndex();
assert(BPIndex && "No Base Pointer Save Slot!");
BPOffset = FFI->getObjectOffset(BPIndex);
} else {
BPOffset = getBasePointerSaveOffset();
}
}
int PBPOffset = 0;
if (FI->usesPICBase()) {
MachineFrameInfo *FFI = MF.getFrameInfo();
int PBPIndex = FI->getPICBasePointerSaveIndex();
assert(PBPIndex && "No PIC Base Pointer Save Slot!");
PBPOffset = FFI->getObjectOffset(PBPIndex);
}
bool UsesTCRet = RetOpcode == PPC::TCRETURNri ||
RetOpcode == PPC::TCRETURNdi ||
RetOpcode == PPC::TCRETURNai ||
RetOpcode == PPC::TCRETURNri8 ||
RetOpcode == PPC::TCRETURNdi8 ||
RetOpcode == PPC::TCRETURNai8;
if (UsesTCRet) {
int MaxTCRetDelta = FI->getTailCallSPDelta();
MachineOperand &StackAdjust = MBBI->getOperand(1);
assert(StackAdjust.isImm() && "Expecting immediate value.");
// Adjust stack pointer.
int StackAdj = StackAdjust.getImm();
int Delta = StackAdj - MaxTCRetDelta;
assert((Delta >= 0) && "Delta must be positive");
if (MaxTCRetDelta>0)
FrameSize += (StackAdj +Delta);
else
FrameSize += StackAdj;
}
// Frames of 32KB & larger require special handling because they cannot be
// indexed into with a simple LD/LWZ immediate offset operand.
bool isLargeFrame = !isInt<16>(FrameSize);
if (FrameSize) {
// In the prologue, the loaded (or persistent) stack pointer value is offset
// by the STDU/STDUX/STWU/STWUX instruction. Add this offset back now.
// If this function contained a fastcc call and GuaranteedTailCallOpt is
// enabled (=> hasFastCall()==true) the fastcc call might contain a tail
// call which invalidates the stack pointer value in SP(0). So we use the
// value of R31 in this case.
if (FI->hasFastCall()) {
assert(HasFP && "Expecting a valid frame pointer.");
if (!isLargeFrame) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(FPReg).addImm(FrameSize);
} else {
BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
.addImm(FrameSize >> 16);
BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addImm(FrameSize & 0xFFFF);
BuildMI(MBB, MBBI, dl, AddInst)
.addReg(SPReg)
.addReg(FPReg)
.addReg(ScratchReg);
}
} else if (!isLargeFrame && !HasBP && !MFI->hasVarSizedObjects()) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(SPReg)
.addImm(FrameSize);
} else {
BuildMI(MBB, MBBI, dl, LoadInst, SPReg)
.addImm(0)
.addReg(SPReg);
}
}
if (MustSaveLR)
BuildMI(MBB, MBBI, dl, LoadInst, ScratchReg)
.addImm(LROffset)
.addReg(SPReg);
assert((isPPC64 || MustSaveCRs.empty()) &&
"Epilogue CR restoring supported only in 64-bit mode");
if (!MustSaveCRs.empty()) // will only occur for PPC64
BuildMI(MBB, MBBI, dl, TII.get(PPC::LWZ8), TempReg)
.addImm(8)
.addReg(SPReg);
if (HasFP)
BuildMI(MBB, MBBI, dl, LoadInst, FPReg)
.addImm(FPOffset)
.addReg(SPReg);
if (FI->usesPICBase())
// FIXME: On PPC32 SVR4, we must not spill before claiming the stackframe.
BuildMI(MBB, MBBI, dl, LoadInst)
.addReg(PPC::R30)
.addImm(PBPOffset)
.addReg(SPReg);
if (HasBP)
BuildMI(MBB, MBBI, dl, LoadInst, BPReg)
.addImm(BPOffset)
.addReg(SPReg);
if (!MustSaveCRs.empty()) // will only occur for PPC64
for (unsigned i = 0, e = MustSaveCRs.size(); i != e; ++i)
BuildMI(MBB, MBBI, dl, TII.get(PPC::MTOCRF8), MustSaveCRs[i])
.addReg(TempReg, getKillRegState(i == e-1));
if (MustSaveLR)
BuildMI(MBB, MBBI, dl, MTLRInst).addReg(ScratchReg);
// Callee pop calling convention. Pop parameter/linkage area. Used for tail
// call optimization
if (MF.getTarget().Options.GuaranteedTailCallOpt &&
(RetOpcode == PPC::BLR || RetOpcode == PPC::BLR8) &&
MF.getFunction()->getCallingConv() == CallingConv::Fast) {
PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
unsigned CallerAllocatedAmt = FI->getMinReservedArea();
if (CallerAllocatedAmt && isInt<16>(CallerAllocatedAmt)) {
BuildMI(MBB, MBBI, dl, AddImmInst, SPReg)
.addReg(SPReg).addImm(CallerAllocatedAmt);
} else {
BuildMI(MBB, MBBI, dl, LoadImmShiftedInst, ScratchReg)
.addImm(CallerAllocatedAmt >> 16);
BuildMI(MBB, MBBI, dl, OrImmInst, ScratchReg)
.addReg(ScratchReg, RegState::Kill)
.addImm(CallerAllocatedAmt & 0xFFFF);
BuildMI(MBB, MBBI, dl, AddInst)
.addReg(SPReg)
.addReg(FPReg)
.addReg(ScratchReg);
}
} else if (RetOpcode == PPC::TCRETURNdi) {
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILB)).
addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset());
} else if (RetOpcode == PPC::TCRETURNri) {
MBBI = MBB.getLastNonDebugInstr();
assert(MBBI->getOperand(0).isReg() && "Expecting register operand.");
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBCTR));
} else if (RetOpcode == PPC::TCRETURNai) {
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBA)).addImm(JumpTarget.getImm());
} else if (RetOpcode == PPC::TCRETURNdi8) {
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILB8)).
addGlobalAddress(JumpTarget.getGlobal(), JumpTarget.getOffset());
} else if (RetOpcode == PPC::TCRETURNri8) {
MBBI = MBB.getLastNonDebugInstr();
assert(MBBI->getOperand(0).isReg() && "Expecting register operand.");
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBCTR8));
} else if (RetOpcode == PPC::TCRETURNai8) {
MBBI = MBB.getLastNonDebugInstr();
MachineOperand &JumpTarget = MBBI->getOperand(0);
BuildMI(MBB, MBBI, dl, TII.get(PPC::TAILBA8)).addImm(JumpTarget.getImm());
}
}
void
PPCFrameLowering::processFunctionBeforeCalleeSavedScan(MachineFunction &MF,
RegScavenger *) const {
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
// Save and clear the LR state.
PPCFunctionInfo *FI = MF.getInfo<PPCFunctionInfo>();
unsigned LR = RegInfo->getRARegister();
FI->setMustSaveLR(MustSaveLR(MF, LR));
MachineRegisterInfo &MRI = MF.getRegInfo();
MRI.setPhysRegUnused(LR);
// Save R31 if necessary
int FPSI = FI->getFramePointerSaveIndex();
bool isPPC64 = Subtarget.isPPC64();
bool isDarwinABI = Subtarget.isDarwinABI();
MachineFrameInfo *MFI = MF.getFrameInfo();
// If the frame pointer save index hasn't been defined yet.
if (!FPSI && needsFP(MF)) {
// Find out what the fix offset of the frame pointer save area.
int FPOffset = getFramePointerSaveOffset();
// Allocate the frame index for frame pointer save area.
FPSI = MFI->CreateFixedObject(isPPC64? 8 : 4, FPOffset, true);
// Save the result.
FI->setFramePointerSaveIndex(FPSI);
}
int BPSI = FI->getBasePointerSaveIndex();
if (!BPSI && RegInfo->hasBasePointer(MF)) {
int BPOffset = getBasePointerSaveOffset();
// Allocate the frame index for the base pointer save area.
BPSI = MFI->CreateFixedObject(isPPC64? 8 : 4, BPOffset, true);
// Save the result.
FI->setBasePointerSaveIndex(BPSI);
}
// Reserve stack space for the PIC Base register (R30).
// Only used in SVR4 32-bit.
if (FI->usesPICBase()) {
int PBPSI = FI->getPICBasePointerSaveIndex();
PBPSI = MFI->CreateFixedObject(4, -8, true);
FI->setPICBasePointerSaveIndex(PBPSI);
}
// Reserve stack space to move the linkage area to in case of a tail call.
int TCSPDelta = 0;
if (MF.getTarget().Options.GuaranteedTailCallOpt &&
(TCSPDelta = FI->getTailCallSPDelta()) < 0) {
MFI->CreateFixedObject(-1 * TCSPDelta, TCSPDelta, true);
}
// For 32-bit SVR4, allocate the nonvolatile CR spill slot iff the
// function uses CR 2, 3, or 4.
if (!isPPC64 && !isDarwinABI &&
(MRI.isPhysRegUsed(PPC::CR2) ||
MRI.isPhysRegUsed(PPC::CR3) ||
MRI.isPhysRegUsed(PPC::CR4))) {
int FrameIdx = MFI->CreateFixedObject((uint64_t)4, (int64_t)-4, true);
FI->setCRSpillFrameIndex(FrameIdx);
}
}
void PPCFrameLowering::processFunctionBeforeFrameFinalized(MachineFunction &MF,
RegScavenger *RS) const {
// Early exit if not using the SVR4 ABI.
if (!Subtarget.isSVR4ABI()) {
addScavengingSpillSlot(MF, RS);
return;
}
// Get callee saved register information.
MachineFrameInfo *FFI = MF.getFrameInfo();
const std::vector<CalleeSavedInfo> &CSI = FFI->getCalleeSavedInfo();
// Early exit if no callee saved registers are modified!
if (CSI.empty() && !needsFP(MF)) {
addScavengingSpillSlot(MF, RS);
return;
}
unsigned MinGPR = PPC::R31;
unsigned MinG8R = PPC::X31;
unsigned MinFPR = PPC::F31;
unsigned MinVR = PPC::V31;
bool HasGPSaveArea = false;
bool HasG8SaveArea = false;
bool HasFPSaveArea = false;
bool HasVRSAVESaveArea = false;
bool HasVRSaveArea = false;
SmallVector<CalleeSavedInfo, 18> GPRegs;
SmallVector<CalleeSavedInfo, 18> G8Regs;
SmallVector<CalleeSavedInfo, 18> FPRegs;
SmallVector<CalleeSavedInfo, 18> VRegs;
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (PPC::GPRCRegClass.contains(Reg)) {
HasGPSaveArea = true;
GPRegs.push_back(CSI[i]);
if (Reg < MinGPR) {
MinGPR = Reg;
}
} else if (PPC::G8RCRegClass.contains(Reg)) {
HasG8SaveArea = true;
G8Regs.push_back(CSI[i]);
if (Reg < MinG8R) {
MinG8R = Reg;
}
} else if (PPC::F8RCRegClass.contains(Reg)) {
HasFPSaveArea = true;
FPRegs.push_back(CSI[i]);
if (Reg < MinFPR) {
MinFPR = Reg;
}
} else if (PPC::CRBITRCRegClass.contains(Reg) ||
PPC::CRRCRegClass.contains(Reg)) {
; // do nothing, as we already know whether CRs are spilled
} else if (PPC::VRSAVERCRegClass.contains(Reg)) {
HasVRSAVESaveArea = true;
} else if (PPC::VRRCRegClass.contains(Reg)) {
HasVRSaveArea = true;
VRegs.push_back(CSI[i]);
if (Reg < MinVR) {
MinVR = Reg;
}
} else {
llvm_unreachable("Unknown RegisterClass!");
}
}
PPCFunctionInfo *PFI = MF.getInfo<PPCFunctionInfo>();
const TargetRegisterInfo *TRI = Subtarget.getRegisterInfo();
int64_t LowerBound = 0;
// Take into account stack space reserved for tail calls.
int TCSPDelta = 0;
if (MF.getTarget().Options.GuaranteedTailCallOpt &&
(TCSPDelta = PFI->getTailCallSPDelta()) < 0) {
LowerBound = TCSPDelta;
}
// The Floating-point register save area is right below the back chain word
// of the previous stack frame.
if (HasFPSaveArea) {
for (unsigned i = 0, e = FPRegs.size(); i != e; ++i) {
int FI = FPRegs[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
LowerBound -= (31 - TRI->getEncodingValue(MinFPR) + 1) * 8;
}
// Check whether the frame pointer register is allocated. If so, make sure it
// is spilled to the correct offset.
if (needsFP(MF)) {
HasGPSaveArea = true;
int FI = PFI->getFramePointerSaveIndex();
assert(FI && "No Frame Pointer Save Slot!");
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
if (PFI->usesPICBase()) {
HasGPSaveArea = true;
int FI = PFI->getPICBasePointerSaveIndex();
assert(FI && "No PIC Base Pointer Save Slot!");
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
const PPCRegisterInfo *RegInfo =
static_cast<const PPCRegisterInfo *>(Subtarget.getRegisterInfo());
if (RegInfo->hasBasePointer(MF)) {
HasGPSaveArea = true;
int FI = PFI->getBasePointerSaveIndex();
assert(FI && "No Base Pointer Save Slot!");
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
// General register save area starts right below the Floating-point
// register save area.
if (HasGPSaveArea || HasG8SaveArea) {
// Move general register save area spill slots down, taking into account
// the size of the Floating-point register save area.
for (unsigned i = 0, e = GPRegs.size(); i != e; ++i) {
int FI = GPRegs[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
// Move general register save area spill slots down, taking into account
// the size of the Floating-point register save area.
for (unsigned i = 0, e = G8Regs.size(); i != e; ++i) {
int FI = G8Regs[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
unsigned MinReg =
std::min<unsigned>(TRI->getEncodingValue(MinGPR),
TRI->getEncodingValue(MinG8R));
if (Subtarget.isPPC64()) {
LowerBound -= (31 - MinReg + 1) * 8;
} else {
LowerBound -= (31 - MinReg + 1) * 4;
}
}
// For 32-bit only, the CR save area is below the general register
// save area. For 64-bit SVR4, the CR save area is addressed relative
// to the stack pointer and hence does not need an adjustment here.
// Only CR2 (the first nonvolatile spilled) has an associated frame
// index so that we have a single uniform save area.
if (spillsCR(MF) && !(Subtarget.isPPC64() && Subtarget.isSVR4ABI())) {
// Adjust the frame index of the CR spill slot.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if ((Subtarget.isSVR4ABI() && Reg == PPC::CR2)
// Leave Darwin logic as-is.
|| (!Subtarget.isSVR4ABI() &&
(PPC::CRBITRCRegClass.contains(Reg) ||
PPC::CRRCRegClass.contains(Reg)))) {
int FI = CSI[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
}
LowerBound -= 4; // The CR save area is always 4 bytes long.
}
if (HasVRSAVESaveArea) {
// FIXME SVR4: Is it actually possible to have multiple elements in CSI
// which have the VRSAVE register class?
// Adjust the frame index of the VRSAVE spill slot.
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
if (PPC::VRSAVERCRegClass.contains(Reg)) {
int FI = CSI[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
}
LowerBound -= 4; // The VRSAVE save area is always 4 bytes long.
}
if (HasVRSaveArea) {
// Insert alignment padding, we need 16-byte alignment.
LowerBound = (LowerBound - 15) & ~(15);
for (unsigned i = 0, e = VRegs.size(); i != e; ++i) {
int FI = VRegs[i].getFrameIdx();
FFI->setObjectOffset(FI, LowerBound + FFI->getObjectOffset(FI));
}
}
addScavengingSpillSlot(MF, RS);
}
void
PPCFrameLowering::addScavengingSpillSlot(MachineFunction &MF,
RegScavenger *RS) const {
// Reserve a slot closest to SP or frame pointer if we have a dynalloc or
// a large stack, which will require scavenging a register to materialize a
// large offset.
// We need to have a scavenger spill slot for spills if the frame size is
// large. In case there is no free register for large-offset addressing,
// this slot is used for the necessary emergency spill. Also, we need the
// slot for dynamic stack allocations.
// The scavenger might be invoked if the frame offset does not fit into
// the 16-bit immediate. We don't know the complete frame size here
// because we've not yet computed callee-saved register spills or the
// needed alignment padding.
unsigned StackSize = determineFrameLayout(MF, false, true);
MachineFrameInfo *MFI = MF.getFrameInfo();
if (MFI->hasVarSizedObjects() || spillsCR(MF) || spillsVRSAVE(MF) ||
hasNonRISpills(MF) || (hasSpills(MF) && !isInt<16>(StackSize))) {
const TargetRegisterClass *GPRC = &PPC::GPRCRegClass;
const TargetRegisterClass *G8RC = &PPC::G8RCRegClass;
const TargetRegisterClass *RC = Subtarget.isPPC64() ? G8RC : GPRC;
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
// Might we have over-aligned allocas?
bool HasAlVars = MFI->hasVarSizedObjects() &&
MFI->getMaxAlignment() > getStackAlignment();
// These kinds of spills might need two registers.
if (spillsCR(MF) || spillsVRSAVE(MF) || HasAlVars)
RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
RC->getAlignment(),
false));
}
}
bool
PPCFrameLowering::spillCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
// Currently, this function only handles SVR4 32- and 64-bit ABIs.
// Return false otherwise to maintain pre-existing behavior.
if (!Subtarget.isSVR4ABI())
return false;
MachineFunction *MF = MBB.getParent();
const PPCInstrInfo &TII =
*static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
DebugLoc DL;
bool CRSpilled = false;
MachineInstrBuilder CRMIB;
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
// Only Darwin actually uses the VRSAVE register, but it can still appear
// here if, for example, @llvm.eh.unwind.init() is used. If we're not on
// Darwin, ignore it.
if (Reg == PPC::VRSAVE && !Subtarget.isDarwinABI())
continue;
// CR2 through CR4 are the nonvolatile CR fields.
bool IsCRField = PPC::CR2 <= Reg && Reg <= PPC::CR4;
// Add the callee-saved register as live-in; it's killed at the spill.
MBB.addLiveIn(Reg);
if (CRSpilled && IsCRField) {
CRMIB.addReg(Reg, RegState::ImplicitKill);
continue;
}
// Insert the spill to the stack frame.
if (IsCRField) {
PPCFunctionInfo *FuncInfo = MF->getInfo<PPCFunctionInfo>();
if (Subtarget.isPPC64()) {
// The actual spill will happen at the start of the prologue.
FuncInfo->addMustSaveCR(Reg);
} else {
CRSpilled = true;
FuncInfo->setSpillsCR();
// 32-bit: FP-relative. Note that we made sure CR2-CR4 all have
// the same frame index in PPCRegisterInfo::hasReservedSpillSlot.
CRMIB = BuildMI(*MF, DL, TII.get(PPC::MFCR), PPC::R12)
.addReg(Reg, RegState::ImplicitKill);
MBB.insert(MI, CRMIB);
MBB.insert(MI, addFrameReference(BuildMI(*MF, DL, TII.get(PPC::STW))
.addReg(PPC::R12,
getKillRegState(true)),
CSI[i].getFrameIdx()));
}
} else {
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.storeRegToStackSlot(MBB, MI, Reg, true,
CSI[i].getFrameIdx(), RC, TRI);
}
}
return true;
}
static void
restoreCRs(bool isPPC64, bool is31,
bool CR2Spilled, bool CR3Spilled, bool CR4Spilled,
MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI, unsigned CSIIndex) {
MachineFunction *MF = MBB.getParent();
const PPCInstrInfo &TII = *MF->getSubtarget<PPCSubtarget>().getInstrInfo();
DebugLoc DL;
unsigned RestoreOp, MoveReg;
if (isPPC64)
// This is handled during epilogue generation.
return;
else {
// 32-bit: FP-relative
MBB.insert(MI, addFrameReference(BuildMI(*MF, DL, TII.get(PPC::LWZ),
PPC::R12),
CSI[CSIIndex].getFrameIdx()));
RestoreOp = PPC::MTOCRF;
MoveReg = PPC::R12;
}
if (CR2Spilled)
MBB.insert(MI, BuildMI(*MF, DL, TII.get(RestoreOp), PPC::CR2)
.addReg(MoveReg, getKillRegState(!CR3Spilled && !CR4Spilled)));
if (CR3Spilled)
MBB.insert(MI, BuildMI(*MF, DL, TII.get(RestoreOp), PPC::CR3)
.addReg(MoveReg, getKillRegState(!CR4Spilled)));
if (CR4Spilled)
MBB.insert(MI, BuildMI(*MF, DL, TII.get(RestoreOp), PPC::CR4)
.addReg(MoveReg, getKillRegState(true)));
}
void PPCFrameLowering::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
const TargetInstrInfo &TII = *Subtarget.getInstrInfo();
if (MF.getTarget().Options.GuaranteedTailCallOpt &&
I->getOpcode() == PPC::ADJCALLSTACKUP) {
// Add (actually subtract) back the amount the callee popped on return.
if (int CalleeAmt = I->getOperand(1).getImm()) {
bool is64Bit = Subtarget.isPPC64();
CalleeAmt *= -1;
unsigned StackReg = is64Bit ? PPC::X1 : PPC::R1;
unsigned TmpReg = is64Bit ? PPC::X0 : PPC::R0;
unsigned ADDIInstr = is64Bit ? PPC::ADDI8 : PPC::ADDI;
unsigned ADDInstr = is64Bit ? PPC::ADD8 : PPC::ADD4;
unsigned LISInstr = is64Bit ? PPC::LIS8 : PPC::LIS;
unsigned ORIInstr = is64Bit ? PPC::ORI8 : PPC::ORI;
MachineInstr *MI = I;
DebugLoc dl = MI->getDebugLoc();
if (isInt<16>(CalleeAmt)) {
BuildMI(MBB, I, dl, TII.get(ADDIInstr), StackReg)
.addReg(StackReg, RegState::Kill)
.addImm(CalleeAmt);
} else {
MachineBasicBlock::iterator MBBI = I;
BuildMI(MBB, MBBI, dl, TII.get(LISInstr), TmpReg)
.addImm(CalleeAmt >> 16);
BuildMI(MBB, MBBI, dl, TII.get(ORIInstr), TmpReg)
.addReg(TmpReg, RegState::Kill)
.addImm(CalleeAmt & 0xFFFF);
BuildMI(MBB, MBBI, dl, TII.get(ADDInstr), StackReg)
.addReg(StackReg, RegState::Kill)
.addReg(TmpReg);
}
}
}
// Simply discard ADJCALLSTACKDOWN, ADJCALLSTACKUP instructions.
MBB.erase(I);
}
bool
PPCFrameLowering::restoreCalleeSavedRegisters(MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const std::vector<CalleeSavedInfo> &CSI,
const TargetRegisterInfo *TRI) const {
// Currently, this function only handles SVR4 32- and 64-bit ABIs.
// Return false otherwise to maintain pre-existing behavior.
if (!Subtarget.isSVR4ABI())
return false;
MachineFunction *MF = MBB.getParent();
const PPCInstrInfo &TII =
*static_cast<const PPCInstrInfo *>(Subtarget.getInstrInfo());
bool CR2Spilled = false;
bool CR3Spilled = false;
bool CR4Spilled = false;
unsigned CSIIndex = 0;
// Initialize insertion-point logic; we will be restoring in reverse
// order of spill.
MachineBasicBlock::iterator I = MI, BeforeI = I;
bool AtStart = I == MBB.begin();
if (!AtStart)
--BeforeI;
for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
unsigned Reg = CSI[i].getReg();
// Only Darwin actually uses the VRSAVE register, but it can still appear
// here if, for example, @llvm.eh.unwind.init() is used. If we're not on
// Darwin, ignore it.
if (Reg == PPC::VRSAVE && !Subtarget.isDarwinABI())
continue;
if (Reg == PPC::CR2) {
CR2Spilled = true;
// The spill slot is associated only with CR2, which is the
// first nonvolatile spilled. Save it here.
CSIIndex = i;
continue;
} else if (Reg == PPC::CR3) {
CR3Spilled = true;
continue;
} else if (Reg == PPC::CR4) {
CR4Spilled = true;
continue;
} else {
// When we first encounter a non-CR register after seeing at
// least one CR register, restore all spilled CRs together.
if ((CR2Spilled || CR3Spilled || CR4Spilled)
&& !(PPC::CR2 <= Reg && Reg <= PPC::CR4)) {
bool is31 = needsFP(*MF);
restoreCRs(Subtarget.isPPC64(), is31,
CR2Spilled, CR3Spilled, CR4Spilled,
MBB, I, CSI, CSIIndex);
CR2Spilled = CR3Spilled = CR4Spilled = false;
}
// Default behavior for non-CR saves.
const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
TII.loadRegFromStackSlot(MBB, I, Reg, CSI[i].getFrameIdx(),
RC, TRI);
assert(I != MBB.begin() &&
"loadRegFromStackSlot didn't insert any code!");
}
// Insert in reverse order.
if (AtStart)
I = MBB.begin();
else {
I = BeforeI;
++I;
}
}
// If we haven't yet spilled the CRs, do so now.
if (CR2Spilled || CR3Spilled || CR4Spilled) {
bool is31 = needsFP(*MF);
restoreCRs(Subtarget.isPPC64(), is31, CR2Spilled, CR3Spilled, CR4Spilled,
MBB, I, CSI, CSIIndex);
}
return true;
}
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