[PPC] Refactor PPCBranchSelector.cpp
This patch splits the huge function PPCBranchSelector.cpp:runOnMachineFunction into several smaller functions. No functional change. Differential Revision: https://reviews.llvm.org/D59623 llvm-svn: 357033
This commit is contained in:
Guozhi Wei
parent
c74271c537
commit
330dcd9dab
|
|
@ -48,6 +48,17 @@ namespace {
|
|||
// size that is due to potential padding.
|
||||
std::vector<std::pair<unsigned, unsigned>> BlockSizes;
|
||||
|
||||
// The first block number which has imprecise instruction address.
|
||||
int FirstImpreciseBlock = -1;
|
||||
|
||||
unsigned GetAlignmentAdjustment(MachineBasicBlock &MBB, unsigned Offset);
|
||||
unsigned ComputeBlockSizes(MachineFunction &Fn);
|
||||
void modifyAdjustment(MachineFunction &Fn);
|
||||
int computeBranchSize(MachineFunction &Fn,
|
||||
const MachineBasicBlock *Src,
|
||||
const MachineBasicBlock *Dest,
|
||||
unsigned BrOffset);
|
||||
|
||||
bool runOnMachineFunction(MachineFunction &Fn) override;
|
||||
|
||||
MachineFunctionProperties getRequiredProperties() const override {
|
||||
|
|
@ -70,47 +81,47 @@ FunctionPass *llvm::createPPCBranchSelectionPass() {
|
|||
return new PPCBSel();
|
||||
}
|
||||
|
||||
bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
||||
const PPCInstrInfo *TII =
|
||||
static_cast<const PPCInstrInfo *>(Fn.getSubtarget().getInstrInfo());
|
||||
// Give the blocks of the function a dense, in-order, numbering.
|
||||
Fn.RenumberBlocks();
|
||||
BlockSizes.resize(Fn.getNumBlockIDs());
|
||||
// The first block number which has imprecise instruction address.
|
||||
int FirstImpreciseBlock = -1;
|
||||
/// In order to make MBB aligned, we need to add an adjustment value to the
|
||||
/// original Offset.
|
||||
unsigned PPCBSel::GetAlignmentAdjustment(MachineBasicBlock &MBB,
|
||||
unsigned Offset) {
|
||||
unsigned Align = MBB.getAlignment();
|
||||
if (!Align)
|
||||
return 0;
|
||||
|
||||
auto GetAlignmentAdjustment = [&FirstImpreciseBlock]
|
||||
(MachineBasicBlock &MBB, unsigned Offset) -> unsigned {
|
||||
unsigned Align = MBB.getAlignment();
|
||||
if (!Align)
|
||||
return 0;
|
||||
unsigned AlignAmt = 1 << Align;
|
||||
unsigned ParentAlign = MBB.getParent()->getAlignment();
|
||||
|
||||
unsigned AlignAmt = 1 << Align;
|
||||
unsigned ParentAlign = MBB.getParent()->getAlignment();
|
||||
if (Align <= ParentAlign)
|
||||
return OffsetToAlignment(Offset, AlignAmt);
|
||||
|
||||
if (Align <= ParentAlign)
|
||||
return OffsetToAlignment(Offset, AlignAmt);
|
||||
// The alignment of this MBB is larger than the function's alignment, so we
|
||||
// can't tell whether or not it will insert nops. Assume that it will.
|
||||
if (FirstImpreciseBlock < 0)
|
||||
FirstImpreciseBlock = MBB.getNumber();
|
||||
return AlignAmt + OffsetToAlignment(Offset, AlignAmt);
|
||||
}
|
||||
|
||||
// The alignment of this MBB is larger than the function's alignment, so we
|
||||
// can't tell whether or not it will insert nops. Assume that it will.
|
||||
if (FirstImpreciseBlock < 0)
|
||||
FirstImpreciseBlock = MBB.getNumber();
|
||||
return AlignAmt + OffsetToAlignment(Offset, AlignAmt);
|
||||
};
|
||||
|
||||
// We need to be careful about the offset of the first block in the function
|
||||
// because it might not have the function's alignment. This happens because,
|
||||
// under the ELFv2 ABI, for functions which require a TOC pointer, we add a
|
||||
// two-instruction sequence to the start of the function.
|
||||
// Note: This needs to be synchronized with the check in
|
||||
// PPCLinuxAsmPrinter::EmitFunctionBodyStart.
|
||||
/// We need to be careful about the offset of the first block in the function
|
||||
/// because it might not have the function's alignment. This happens because,
|
||||
/// under the ELFv2 ABI, for functions which require a TOC pointer, we add a
|
||||
/// two-instruction sequence to the start of the function.
|
||||
/// Note: This needs to be synchronized with the check in
|
||||
/// PPCLinuxAsmPrinter::EmitFunctionBodyStart.
|
||||
static inline unsigned GetInitialOffset(MachineFunction &Fn) {
|
||||
unsigned InitialOffset = 0;
|
||||
if (Fn.getSubtarget<PPCSubtarget>().isELFv2ABI() &&
|
||||
!Fn.getRegInfo().use_empty(PPC::X2))
|
||||
InitialOffset = 8;
|
||||
return InitialOffset;
|
||||
}
|
||||
|
||||
/// Measure each MBB and compute a size for the entire function.
|
||||
unsigned PPCBSel::ComputeBlockSizes(MachineFunction &Fn) {
|
||||
const PPCInstrInfo *TII =
|
||||
static_cast<const PPCInstrInfo *>(Fn.getSubtarget().getInstrInfo());
|
||||
unsigned FuncSize = GetInitialOffset(Fn);
|
||||
|
||||
// Measure each MBB and compute a size for the entire function.
|
||||
unsigned FuncSize = InitialOffset;
|
||||
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
|
||||
++MFI) {
|
||||
MachineBasicBlock *MBB = &*MFI;
|
||||
|
|
@ -138,6 +149,135 @@ bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
|||
FuncSize += BlockSize;
|
||||
}
|
||||
|
||||
return FuncSize;
|
||||
}
|
||||
|
||||
/// Modify the basic block align adjustment.
|
||||
void PPCBSel::modifyAdjustment(MachineFunction &Fn) {
|
||||
unsigned Offset = GetInitialOffset(Fn);
|
||||
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
|
||||
++MFI) {
|
||||
MachineBasicBlock *MBB = &*MFI;
|
||||
|
||||
if (MBB->getNumber() > 0) {
|
||||
auto &BS = BlockSizes[MBB->getNumber()-1];
|
||||
BS.first -= BS.second;
|
||||
Offset -= BS.second;
|
||||
|
||||
unsigned AlignExtra = GetAlignmentAdjustment(*MBB, Offset);
|
||||
|
||||
BS.first += AlignExtra;
|
||||
BS.second = AlignExtra;
|
||||
|
||||
Offset += AlignExtra;
|
||||
}
|
||||
|
||||
Offset += BlockSizes[MBB->getNumber()].first;
|
||||
}
|
||||
}
|
||||
|
||||
/// Determine the offset from the branch in Src block to the Dest block.
|
||||
/// BrOffset is the offset of the branch instruction inside Src block.
|
||||
int PPCBSel::computeBranchSize(MachineFunction &Fn,
|
||||
const MachineBasicBlock *Src,
|
||||
const MachineBasicBlock *Dest,
|
||||
unsigned BrOffset) {
|
||||
int BranchSize;
|
||||
unsigned MaxAlign = 2;
|
||||
bool NeedExtraAdjustment = false;
|
||||
if (Dest->getNumber() <= Src->getNumber()) {
|
||||
// If this is a backwards branch, the delta is the offset from the
|
||||
// start of this block to this branch, plus the sizes of all blocks
|
||||
// from this block to the dest.
|
||||
BranchSize = BrOffset;
|
||||
MaxAlign = std::max(MaxAlign, Src->getAlignment());
|
||||
|
||||
int DestBlock = Dest->getNumber();
|
||||
BranchSize += BlockSizes[DestBlock].first;
|
||||
for (unsigned i = DestBlock+1, e = Src->getNumber(); i < e; ++i) {
|
||||
BranchSize += BlockSizes[i].first;
|
||||
MaxAlign = std::max(MaxAlign,
|
||||
Fn.getBlockNumbered(i)->getAlignment());
|
||||
}
|
||||
|
||||
NeedExtraAdjustment = (FirstImpreciseBlock >= 0) &&
|
||||
(DestBlock >= FirstImpreciseBlock);
|
||||
} else {
|
||||
// Otherwise, add the size of the blocks between this block and the
|
||||
// dest to the number of bytes left in this block.
|
||||
unsigned StartBlock = Src->getNumber();
|
||||
BranchSize = BlockSizes[StartBlock].first - BrOffset;
|
||||
|
||||
MaxAlign = std::max(MaxAlign, Dest->getAlignment());
|
||||
for (unsigned i = StartBlock+1, e = Dest->getNumber(); i != e; ++i) {
|
||||
BranchSize += BlockSizes[i].first;
|
||||
MaxAlign = std::max(MaxAlign,
|
||||
Fn.getBlockNumbered(i)->getAlignment());
|
||||
}
|
||||
|
||||
NeedExtraAdjustment = (FirstImpreciseBlock >= 0) &&
|
||||
(Src->getNumber() >= FirstImpreciseBlock);
|
||||
}
|
||||
|
||||
// We tend to over estimate code size due to large alignment and
|
||||
// inline assembly. Usually it causes larger computed branch offset.
|
||||
// But sometimes it may also causes smaller computed branch offset
|
||||
// than actual branch offset. If the offset is close to the limit of
|
||||
// encoding, it may cause problem at run time.
|
||||
// Following is a simplified example.
|
||||
//
|
||||
// actual estimated
|
||||
// address address
|
||||
// ...
|
||||
// bne Far 100 10c
|
||||
// .p2align 4
|
||||
// Near: 110 110
|
||||
// ...
|
||||
// Far: 8108 8108
|
||||
//
|
||||
// Actual offset: 0x8108 - 0x100 = 0x8008
|
||||
// Computed offset: 0x8108 - 0x10c = 0x7ffc
|
||||
//
|
||||
// This example also shows when we can get the largest gap between
|
||||
// estimated offset and actual offset. If there is an aligned block
|
||||
// ABB between branch and target, assume its alignment is <align>
|
||||
// bits. Now consider the accumulated function size FSIZE till the end
|
||||
// of previous block PBB. If the estimated FSIZE is multiple of
|
||||
// 2^<align>, we don't need any padding for the estimated address of
|
||||
// ABB. If actual FSIZE at the end of PBB is 4 bytes more than
|
||||
// multiple of 2^<align>, then we need (2^<align> - 4) bytes of
|
||||
// padding. It also means the actual branch offset is (2^<align> - 4)
|
||||
// larger than computed offset. Other actual FSIZE needs less padding
|
||||
// bytes, so causes smaller gap between actual and computed offset.
|
||||
//
|
||||
// On the other hand, if the inline asm or large alignment occurs
|
||||
// between the branch block and destination block, the estimated address
|
||||
// can be <delta> larger than actual address. If padding bytes are
|
||||
// needed for a later aligned block, the actual number of padding bytes
|
||||
// is at most <delta> more than estimated padding bytes. So the actual
|
||||
// aligned block address is less than or equal to the estimated aligned
|
||||
// block address. So the actual branch offset is less than or equal to
|
||||
// computed branch offset.
|
||||
//
|
||||
// The computed offset is at most ((1 << alignment) - 4) bytes smaller
|
||||
// than actual offset. So we add this number to the offset for safety.
|
||||
if (NeedExtraAdjustment)
|
||||
BranchSize += (1 << MaxAlign) - 4;
|
||||
|
||||
return BranchSize;
|
||||
}
|
||||
|
||||
bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
||||
const PPCInstrInfo *TII =
|
||||
static_cast<const PPCInstrInfo *>(Fn.getSubtarget().getInstrInfo());
|
||||
// Give the blocks of the function a dense, in-order, numbering.
|
||||
Fn.RenumberBlocks();
|
||||
BlockSizes.resize(Fn.getNumBlockIDs());
|
||||
FirstImpreciseBlock = -1;
|
||||
|
||||
// Measure each MBB and compute a size for the entire function.
|
||||
unsigned FuncSize = ComputeBlockSizes(Fn);
|
||||
|
||||
// If the entire function is smaller than the displacement of a branch field,
|
||||
// we know we don't need to shrink any branches in this function. This is a
|
||||
// common case.
|
||||
|
|
@ -185,87 +325,7 @@ bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
|||
|
||||
// Determine the offset from the current branch to the destination
|
||||
// block.
|
||||
int BranchSize;
|
||||
unsigned MaxAlign = 2;
|
||||
bool NeedExtraAdjustment = false;
|
||||
if (Dest->getNumber() <= MBB.getNumber()) {
|
||||
// If this is a backwards branch, the delta is the offset from the
|
||||
// start of this block to this branch, plus the sizes of all blocks
|
||||
// from this block to the dest.
|
||||
BranchSize = MBBStartOffset;
|
||||
MaxAlign = std::max(MaxAlign, MBB.getAlignment());
|
||||
|
||||
int DestBlock = Dest->getNumber();
|
||||
BranchSize += BlockSizes[DestBlock].first;
|
||||
for (unsigned i = DestBlock+1, e = MBB.getNumber(); i < e; ++i) {
|
||||
BranchSize += BlockSizes[i].first;
|
||||
MaxAlign = std::max(MaxAlign,
|
||||
Fn.getBlockNumbered(i)->getAlignment());
|
||||
}
|
||||
|
||||
NeedExtraAdjustment = (FirstImpreciseBlock >= 0) &&
|
||||
(DestBlock >= FirstImpreciseBlock);
|
||||
} else {
|
||||
// Otherwise, add the size of the blocks between this block and the
|
||||
// dest to the number of bytes left in this block.
|
||||
unsigned StartBlock = MBB.getNumber();
|
||||
BranchSize = BlockSizes[StartBlock].first - MBBStartOffset;
|
||||
|
||||
MaxAlign = std::max(MaxAlign, Dest->getAlignment());
|
||||
for (unsigned i = StartBlock+1, e = Dest->getNumber(); i != e; ++i) {
|
||||
BranchSize += BlockSizes[i].first;
|
||||
MaxAlign = std::max(MaxAlign,
|
||||
Fn.getBlockNumbered(i)->getAlignment());
|
||||
}
|
||||
|
||||
NeedExtraAdjustment = (FirstImpreciseBlock >= 0) &&
|
||||
(MBB.getNumber() >= FirstImpreciseBlock);
|
||||
}
|
||||
|
||||
// We tend to over estimate code size due to large alignment and
|
||||
// inline assembly. Usually it causes larger computed branch offset.
|
||||
// But sometimes it may also causes smaller computed branch offset
|
||||
// than actual branch offset. If the offset is close to the limit of
|
||||
// encoding, it may cause problem at run time.
|
||||
// Following is a simplified example.
|
||||
//
|
||||
// actual estimated
|
||||
// address address
|
||||
// ...
|
||||
// bne Far 100 10c
|
||||
// .p2align 4
|
||||
// Near: 110 110
|
||||
// ...
|
||||
// Far: 8108 8108
|
||||
//
|
||||
// Actual offset: 0x8108 - 0x100 = 0x8008
|
||||
// Computed offset: 0x8108 - 0x10c = 0x7ffc
|
||||
//
|
||||
// This example also shows when we can get the largest gap between
|
||||
// estimated offset and actual offset. If there is an aligned block
|
||||
// ABB between branch and target, assume its alignment is <align>
|
||||
// bits. Now consider the accumulated function size FSIZE till the end
|
||||
// of previous block PBB. If the estimated FSIZE is multiple of
|
||||
// 2^<align>, we don't need any padding for the estimated address of
|
||||
// ABB. If actual FSIZE at the end of PBB is 4 bytes more than
|
||||
// multiple of 2^<align>, then we need (2^<align> - 4) bytes of
|
||||
// padding. It also means the actual branch offset is (2^<align> - 4)
|
||||
// larger than computed offset. Other actual FSIZE needs less padding
|
||||
// bytes, so causes smaller gap between actual and computed offset.
|
||||
//
|
||||
// On the other hand, if the inline asm or large alignment occurs
|
||||
// between the branch block and destination block, the estimated address
|
||||
// can be <delta> larger than actual address. If padding bytes are
|
||||
// needed for a later aligned block, the actual number of padding bytes
|
||||
// is at most <delta> more than estimated padding bytes. So the actual
|
||||
// aligned block address is less than or equal to the estimated aligned
|
||||
// block address. So the actual branch offset is less than or equal to
|
||||
// computed branch offset.
|
||||
//
|
||||
// The computed offset is at most ((1 << alignment) - 4) bytes smaller
|
||||
// than actual offset. So we add this number to the offset for safety.
|
||||
if (NeedExtraAdjustment)
|
||||
BranchSize += (1 << MaxAlign) - 4;
|
||||
int BranchSize = computeBranchSize(Fn, &MBB, Dest, MBBStartOffset);
|
||||
|
||||
// If this branch is in range, ignore it.
|
||||
if (isInt<16>(BranchSize)) {
|
||||
|
|
@ -324,26 +384,7 @@ bool PPCBSel::runOnMachineFunction(MachineFunction &Fn) {
|
|||
if (MadeChange) {
|
||||
// If we're going to iterate again, make sure we've updated our
|
||||
// padding-based contributions to the block sizes.
|
||||
unsigned Offset = InitialOffset;
|
||||
for (MachineFunction::iterator MFI = Fn.begin(), E = Fn.end(); MFI != E;
|
||||
++MFI) {
|
||||
MachineBasicBlock *MBB = &*MFI;
|
||||
|
||||
if (MBB->getNumber() > 0) {
|
||||
auto &BS = BlockSizes[MBB->getNumber()-1];
|
||||
BS.first -= BS.second;
|
||||
Offset -= BS.second;
|
||||
|
||||
unsigned AlignExtra = GetAlignmentAdjustment(*MBB, Offset);
|
||||
|
||||
BS.first += AlignExtra;
|
||||
BS.second = AlignExtra;
|
||||
|
||||
Offset += AlignExtra;
|
||||
}
|
||||
|
||||
Offset += BlockSizes[MBB->getNumber()].first;
|
||||
}
|
||||
modifyAdjustment(Fn);
|
||||
}
|
||||
|
||||
EverMadeChange |= MadeChange;
|
||||
|
|
|
|||
Loading…
Reference in New Issue