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[Machine Combiner] Refactor machine reassociation code to be target-independent.

Browse Source 
No functional change intended.
Patch by Haicheng Wu <haicheng@codeaurora.org>!

http://reviews.llvm.org/D12887
PR24522

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@248164 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chad Rosier 2015-09-21 15:09:11 +00:00
parent 7dfb31c329
commit c5d4530d42
9 changed files with 294 additions and 515 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

24
include/llvm/CodeGen/MachineCombinerPattern.h
View File

@ -22,7 +22,29 @@ namespace llvm {
///
namespace MachineCombinerPattern {
// Forward declaration
enum MC_PATTERN : int;
enum MC_PATTERN : int {
// These are commutative variants for reassociating a computation chain. See
// the comments before getMachineCombinerPatterns() in TargetInstrInfo.cpp.
MC_REASSOC_AX_BY = 0,
MC_REASSOC_AX_YB = 1,
MC_REASSOC_XA_BY = 2,
MC_REASSOC_XA_YB = 3,
/// Enumeration of instruction pattern supported by AArch64 machine combiner
MC_NONE,
MC_MULADDW_OP1,
MC_MULADDW_OP2,
MC_MULSUBW_OP1,
MC_MULSUBW_OP2,
MC_MULADDWI_OP1,
MC_MULSUBWI_OP1,
MC_MULADDX_OP1,
MC_MULADDX_OP2,
MC_MULSUBX_OP1,
MC_MULSUBX_OP2,
MC_MULADDXI_OP1,
MC_MULSUBXI_OP1
};
} // end namespace MachineCombinerPattern
} // end namespace llvm

37
include/llvm/Target/TargetInstrInfo.h
View File

@ -727,10 +727,27 @@ public:
/// \param Pattern - Vector of possible combination patterns
virtual bool getMachineCombinerPatterns(
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Pattern) const {
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const;
/// Return true if the input \P Inst is part of a chain of dependent ops
/// that are suitable for reassociation, otherwise return false.
/// If the instruction's operands must be commuted to have a previous
/// instruction of the same type define the first source operand, \P Commuted
/// will be set to true.
bool isReassociationCandidate(const MachineInstr &Inst, bool &Commuted) const;
/// Return true when \P Inst is both associative and commutative.
virtual bool isAssociativeAndCommutative(const MachineInstr &Inst) const {
return false;
}
/// Return true when \P Inst has reassociable operands in the same \P MBB.
virtual bool hasReassociableOperands(const MachineInstr &Inst,
const MachineBasicBlock *MBB) const;
/// Return true when \P Inst has reassociable sibling.
bool hasReassociableSibling(const MachineInstr &Inst, bool &Commuted) const;
/// When getMachineCombinerPatterns() finds patterns, this function generates
/// the instructions that could replace the original code sequence. The client
/// has to decide whether the actual replacement is beneficial or not.
@ -745,9 +762,23 @@ public:
MachineInstr &Root, MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const {
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const;
/// Attempt to reassociate \P Root and \P Prev according to \P Pattern to
/// reduce critical path length.
void reassociateOps(MachineInstr &Root, MachineInstr &Prev,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const;
/// This is an architecture-specific helper function of reassociateOps.
/// Set special operand attributes for new instructions after reassociation.
virtual void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,
MachineInstr &NewMI1,
MachineInstr &NewMI2) const {
return;
}
};
/// Return true when a target supports MachineCombiner.
virtual bool useMachineCombiner() const { return false; }

210
lib/CodeGen/TargetInstrInfo.cpp
View File

@ -511,6 +511,216 @@ MachineInstr *TargetInstrInfo::foldMemoryOperand(MachineBasicBlock::iterator MI,
return --Pos;
}
bool TargetInstrInfo::hasReassociableOperands(
const MachineInstr &Inst, const MachineBasicBlock *MBB) const {
const MachineOperand &Op1 = Inst.getOperand(1);
const MachineOperand &Op2 = Inst.getOperand(2);
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
// We need virtual register definitions for the operands that we will
// reassociate.
MachineInstr *MI1 = nullptr;
MachineInstr *MI2 = nullptr;
if (Op1.isReg() && TargetRegisterInfo::isVirtualRegister(Op1.getReg()))
MI1 = MRI.getUniqueVRegDef(Op1.getReg());
if (Op2.isReg() && TargetRegisterInfo::isVirtualRegister(Op2.getReg()))
MI2 = MRI.getUniqueVRegDef(Op2.getReg());
// And they need to be in the trace (otherwise, they won't have a depth).
if (MI1 && MI2 && MI1->getParent() == MBB && MI2->getParent() == MBB)
return true;
return false;
}
bool TargetInstrInfo::hasReassociableSibling(const MachineInstr &Inst,
bool &Commuted) const {
const MachineBasicBlock *MBB = Inst.getParent();
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
MachineInstr *MI1 = MRI.getUniqueVRegDef(Inst.getOperand(1).getReg());
MachineInstr *MI2 = MRI.getUniqueVRegDef(Inst.getOperand(2).getReg());
unsigned AssocOpcode = Inst.getOpcode();
// If only one operand has the same opcode and it's the second source operand,
// the operands must be commuted.
Commuted = MI1->getOpcode() != AssocOpcode && MI2->getOpcode() == AssocOpcode;
if (Commuted)
std::swap(MI1, MI2);
// 1. The previous instruction must be the same type as Inst.
// 2. The previous instruction must have virtual register definitions for its
// operands in the same basic block as Inst.
// 3. The previous instruction's result must only be used by Inst.
if (MI1->getOpcode() == AssocOpcode && hasReassociableOperands(*MI1, MBB) &&
MRI.hasOneNonDBGUse(MI1->getOperand(0).getReg()))
return true;
return false;
}
// 1. The operation must be associative and commutative.
// 2. The instruction must have virtual register definitions for its
// operands in the same basic block.
// 3. The instruction must have a reassociable sibling.
bool TargetInstrInfo::isReassociationCandidate(const MachineInstr &Inst,
bool &Commuted) const {
if (isAssociativeAndCommutative(Inst) &&
hasReassociableOperands(Inst, Inst.getParent()) &&
hasReassociableSibling(Inst, Commuted))
return true;
return false;
}
// The concept of the reassociation pass is that these operations can benefit
// from this kind of transformation:
//
// A = ? op ?
// B = A op X (Prev)
// C = B op Y (Root)
// -->
// A = ? op ?
// B = X op Y
// C = A op B
//
// breaking the dependency between A and B, allowing them to be executed in
// parallel (or back-to-back in a pipeline) instead of depending on each other.
// FIXME: This has the potential to be expensive (compile time) while not
// improving the code at all. Some ways to limit the overhead:
// 1. Track successful transforms; bail out if hit rate gets too low.
// 2. Only enable at -O3 or some other non-default optimization level.
// 3. Pre-screen pattern candidates here: if an operand of the previous
// instruction is known to not increase the critical path, then don't match
// that pattern.
bool TargetInstrInfo::getMachineCombinerPatterns(
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
bool Commute;
if (isReassociationCandidate(Root, Commute)) {
// We found a sequence of instructions that may be suitable for a
// reassociation of operands to increase ILP. Specify each commutation
// possibility for the Prev instruction in the sequence and let the
// machine combiner decide if changing the operands is worthwhile.
if (Commute) {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_YB);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_YB);
} else {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_BY);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_BY);
}
return true;
}
return false;
}
/// Attempt the reassociation transformation to reduce critical path length.
/// See the above comments before getMachineCombinerPatterns().
void TargetInstrInfo::reassociateOps(
MachineInstr &Root, MachineInstr &Prev,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const {
MachineFunction *MF = Root.getParent()->getParent();
MachineRegisterInfo &MRI = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
const TargetRegisterClass *RC = Root.getRegClassConstraint(0, TII, TRI);
// This array encodes the operand index for each parameter because the
// operands may be commuted. Each row corresponds to a pattern value,
// and each column specifies the index of A, B, X, Y.
unsigned OpIdx[4][4] = {
{ 1, 1, 2, 2 },
{ 1, 2, 2, 1 },
{ 2, 1, 1, 2 },
{ 2, 2, 1, 1 }
};
MachineOperand &OpA = Prev.getOperand(OpIdx[Pattern][0]);
MachineOperand &OpB = Root.getOperand(OpIdx[Pattern][1]);
MachineOperand &OpX = Prev.getOperand(OpIdx[Pattern][2]);
MachineOperand &OpY = Root.getOperand(OpIdx[Pattern][3]);
MachineOperand &OpC = Root.getOperand(0);
unsigned RegA = OpA.getReg();
unsigned RegB = OpB.getReg();
unsigned RegX = OpX.getReg();
unsigned RegY = OpY.getReg();
unsigned RegC = OpC.getReg();
if (TargetRegisterInfo::isVirtualRegister(RegA))
MRI.constrainRegClass(RegA, RC);
if (TargetRegisterInfo::isVirtualRegister(RegB))
MRI.constrainRegClass(RegB, RC);
if (TargetRegisterInfo::isVirtualRegister(RegX))
MRI.constrainRegClass(RegX, RC);
if (TargetRegisterInfo::isVirtualRegister(RegY))
MRI.constrainRegClass(RegY, RC);
if (TargetRegisterInfo::isVirtualRegister(RegC))
MRI.constrainRegClass(RegC, RC);
// Create a new virtual register for the result of (X op Y) instead of
// recycling RegB because the MachineCombiner's computation of the critical
// path requires a new register definition rather than an existing one.
unsigned NewVR = MRI.createVirtualRegister(RC);
InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
unsigned Opcode = Root.getOpcode();
bool KillA = OpA.isKill();
bool KillX = OpX.isKill();
bool KillY = OpY.isKill();
// Create new instructions for insertion.
MachineInstrBuilder MIB1 =
BuildMI(*MF, Prev.getDebugLoc(), TII->get(Opcode), NewVR)
.addReg(RegX, getKillRegState(KillX))
.addReg(RegY, getKillRegState(KillY));
MachineInstrBuilder MIB2 =
BuildMI(*MF, Root.getDebugLoc(), TII->get(Opcode), RegC)
.addReg(RegA, getKillRegState(KillA))
.addReg(NewVR, getKillRegState(true));
setSpecialOperandAttr(Root, Prev, *MIB1, *MIB2);
// Record new instructions for insertion and old instructions for deletion.
InsInstrs.push_back(MIB1);
InsInstrs.push_back(MIB2);
DelInstrs.push_back(&Prev);
DelInstrs.push_back(&Root);
}
void TargetInstrInfo::genAlternativeCodeSequence(
MachineInstr &Root, MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstIdxForVirtReg) const {
MachineRegisterInfo &MRI = Root.getParent()->getParent()->getRegInfo();
// Select the previous instruction in the sequence based on the input pattern.
MachineInstr *Prev = nullptr;
switch (Pattern) {
case MachineCombinerPattern::MC_REASSOC_AX_BY:
case MachineCombinerPattern::MC_REASSOC_XA_BY:
Prev = MRI.getUniqueVRegDef(Root.getOperand(1).getReg());
break;
case MachineCombinerPattern::MC_REASSOC_AX_YB:
case MachineCombinerPattern::MC_REASSOC_XA_YB:
Prev = MRI.getUniqueVRegDef(Root.getOperand(2).getReg());
break;
default:
break;
}
assert(Prev && "Unknown pattern for machine combiner");
reassociateOps(Root, *Prev, Pattern, InsInstrs, DelInstrs, InstIdxForVirtReg);
return;
}
/// foldMemoryOperand - Same as the previous version except it allows folding
/// of any load and store from / to any address, not just from a specific
/// stack slot.

1
lib/Target/AArch64/AArch64InstrInfo.cpp
View File

@ -12,7 +12,6 @@
//===----------------------------------------------------------------------===//
#include "AArch64InstrInfo.h"
#include "AArch64MachineCombinerPattern.h"
#include "AArch64Subtarget.h"
#include "MCTargetDesc/AArch64AddressingModes.h"
#include "llvm/CodeGen/MachineFrameInfo.h"

42
lib/Target/AArch64/AArch64MachineCombinerPattern.h
View File

@ -1,42 +0,0 @@
//===- AArch64MachineCombinerPattern.h -===//
//===- AArch64 instruction pattern supported by combiner -===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines instruction pattern supported by combiner
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_LIB_TARGET_AARCH64_AARCH64MACHINECOMBINERPATTERN_H
#define LLVM_LIB_TARGET_AARCH64_AARCH64MACHINECOMBINERPATTERN_H
namespace llvm {
/// Enumeration of instruction pattern supported by machine combiner
///
///
namespace MachineCombinerPattern {
enum MC_PATTERN : int {
MC_NONE = 0,
MC_MULADDW_OP1 = 1,
MC_MULADDW_OP2 = 2,
MC_MULSUBW_OP1 = 3,
MC_MULSUBW_OP2 = 4,
MC_MULADDWI_OP1 = 5,
MC_MULSUBWI_OP1 = 6,
MC_MULADDX_OP1 = 7,
MC_MULADDX_OP2 = 8,
MC_MULSUBX_OP1 = 9,
MC_MULSUBX_OP2 = 10,
MC_MULADDXI_OP1 = 11,
MC_MULSUBXI_OP1 = 12
};
} // end namespace MachineCombinerPattern
} // end namespace llvm
#endif

217
lib/Target/PowerPC/PPCInstrInfo.cpp
View File

@ -189,73 +189,13 @@ int PPCInstrInfo::getOperandLatency(const InstrItineraryData *ItinData,
return Latency;
}
static bool hasVirtualRegDefsInBasicBlock(const MachineInstr &Inst,
const MachineBasicBlock *MBB) {
const MachineOperand &Op1 = Inst.getOperand(1);
const MachineOperand &Op2 = Inst.getOperand(2);
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
// We need virtual register definitions.
MachineInstr *MI1 = nullptr;
MachineInstr *MI2 = nullptr;
if (Op1.isReg() && TargetRegisterInfo::isVirtualRegister(Op1.getReg()))
MI1 = MRI.getUniqueVRegDef(Op1.getReg());
if (Op2.isReg() && TargetRegisterInfo::isVirtualRegister(Op2.getReg()))
MI2 = MRI.getUniqueVRegDef(Op2.getReg());
// And they need to be in the trace (otherwise, they won't have a depth).
if (MI1 && MI2 && MI1->getParent() == MBB && MI2->getParent() == MBB)
return true;
return false;
}
static bool hasReassocSibling(const MachineInstr &Inst, bool &Commuted) {
const MachineBasicBlock *MBB = Inst.getParent();
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
MachineInstr *MI1 = MRI.getUniqueVRegDef(Inst.getOperand(1).getReg());
MachineInstr *MI2 = MRI.getUniqueVRegDef(Inst.getOperand(2).getReg());
unsigned AssocOpcode = Inst.getOpcode();
// If only one operand has the same opcode and it's the second source operand,
// the operands must be commuted.
Commuted = MI1->getOpcode() != AssocOpcode && MI2->getOpcode() == AssocOpcode;
if (Commuted)
std::swap(MI1, MI2);
// 1. The previous instruction must be the same type as Inst.
// 2. The previous instruction must have virtual register definitions for its
// operands in the same basic block as Inst.
// 3. The previous instruction's result must only be used by Inst.
if (MI1->getOpcode() == AssocOpcode &&
hasVirtualRegDefsInBasicBlock(*MI1, MBB) &&
MRI.hasOneNonDBGUse(MI1->getOperand(0).getReg()))
return true;
return false;
}
// This function does not list all associative and commutative operations, but
// only those worth feeding through the machine combiner in an attempt to
// reduce the critical path. Mostly, this means floating-point operations,
// because they have high latencies (compared to other operations, such and
// and/or, which are also associative and commutative, but have low latencies).
//
// The concept is that these operations can benefit from this kind of
// transformation:
//
// A = ? op ?
// B = A op X
// C = B op Y
// -->
// A = ? op ?
// B = X op Y
// C = A op B
//
// breaking the dependency between A and B, allowing them to be executed in
// parallel (or back-to-back in a pipeline) instead of depending on each other.
static bool isAssociativeAndCommutative(unsigned Opcode) {
switch (Opcode) {
bool PPCInstrInfo::isAssociativeAndCommutative(const MachineInstr &Inst) const {
switch (Inst.getOpcode()) {
// FP Add:
case PPC::FADD:
case PPC::FADDS:
@ -288,26 +228,9 @@ static bool isAssociativeAndCommutative(unsigned Opcode) {
}
}
/// Return true if the input instruction is part of a chain of dependent ops
/// that are suitable for reassociation, otherwise return false.
/// If the instruction's operands must be commuted to have a previous
/// instruction of the same type define the first source operand, Commuted will
/// be set to true.
static bool isReassocCandidate(const MachineInstr &Inst, bool &Commuted) {
// 1. The operation must be associative and commutative.
// 2. The instruction must have virtual register definitions for its
// operands in the same basic block.
// 3. The instruction must have a reassociable sibling.
if (isAssociativeAndCommutative(Inst.getOpcode()) &&
hasVirtualRegDefsInBasicBlock(Inst, Inst.getParent()) &&
hasReassocSibling(Inst, Commuted))
return true;
return false;
}
bool PPCInstrInfo::getMachineCombinerPatterns(MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
bool PPCInstrInfo::getMachineCombinerPatterns(
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
// Using the machine combiner in this way is potentially expensive, so
// restrict to when aggressive optimizations are desired.
if (Subtarget.getTargetMachine().getOptLevel() != CodeGenOpt::Aggressive)
@ -317,135 +240,7 @@ bool PPCInstrInfo::getMachineCombinerPatterns(MachineInstr &Root,
if (!Root.getParent()->getParent()->getTarget().Options.UnsafeFPMath)
return false;
// Look for this reassociation pattern:
// B = A op X (Prev)
// C = B op Y (Root)
// FIXME: We should also match FMA operations here, where we consider the
// 'part' of the FMA, either the addition or the multiplication, paired with
// an actual addition or multiplication.
bool Commute;
if (isReassocCandidate(Root, Commute)) {
// We found a sequence of instructions that may be suitable for a
// reassociation of operands to increase ILP. Specify each commutation
// possibility for the Prev instruction in the sequence and let the
// machine combiner decide if changing the operands is worthwhile.
if (Commute) {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_YB);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_YB);
} else {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_BY);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_BY);
}
return true;
}
return false;
}
/// Attempt the following reassociation to reduce critical path length:
/// B = A op X (Prev)
/// C = B op Y (Root)
/// ===>
/// B = X op Y
/// C = A op B
static void reassociateOps(MachineInstr &Root, MachineInstr &Prev,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) {
MachineFunction *MF = Root.getParent()->getParent();
MachineRegisterInfo &MRI = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
const TargetRegisterClass *RC = Root.getRegClassConstraint(0, TII, TRI);
// This array encodes the operand index for each parameter because the
// operands may be commuted. Each row corresponds to a pattern value,
// and each column specifies the index of A, B, X, Y.
unsigned OpIdx[4][4] = {
{ 1, 1, 2, 2 },
{ 1, 2, 2, 1 },
{ 2, 1, 1, 2 },
{ 2, 2, 1, 1 }
};
MachineOperand &OpA = Prev.getOperand(OpIdx[Pattern][0]);
MachineOperand &OpB = Root.getOperand(OpIdx[Pattern][1]);
MachineOperand &OpX = Prev.getOperand(OpIdx[Pattern][2]);
MachineOperand &OpY = Root.getOperand(OpIdx[Pattern][3]);
MachineOperand &OpC = Root.getOperand(0);
unsigned RegA = OpA.getReg();
unsigned RegB = OpB.getReg();
unsigned RegX = OpX.getReg();
unsigned RegY = OpY.getReg();
unsigned RegC = OpC.getReg();
if (TargetRegisterInfo::isVirtualRegister(RegA))
MRI.constrainRegClass(RegA, RC);
if (TargetRegisterInfo::isVirtualRegister(RegB))
MRI.constrainRegClass(RegB, RC);
if (TargetRegisterInfo::isVirtualRegister(RegX))
MRI.constrainRegClass(RegX, RC);
if (TargetRegisterInfo::isVirtualRegister(RegY))
MRI.constrainRegClass(RegY, RC);
if (TargetRegisterInfo::isVirtualRegister(RegC))
MRI.constrainRegClass(RegC, RC);
// Create a new virtual register for the result of (X op Y) instead of
// recycling RegB because the MachineCombiner's computation of the critical
// path requires a new register definition rather than an existing one.
unsigned NewVR = MRI.createVirtualRegister(RC);
InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
unsigned Opcode = Root.getOpcode();
bool KillA = OpA.isKill();
bool KillX = OpX.isKill();
bool KillY = OpY.isKill();
// Create new instructions for insertion.
MachineInstrBuilder MIB1 =
BuildMI(*MF, Prev.getDebugLoc(), TII->get(Opcode), NewVR)
.addReg(RegX, getKillRegState(KillX))
.addReg(RegY, getKillRegState(KillY));
InsInstrs.push_back(MIB1);
MachineInstrBuilder MIB2 =
BuildMI(*MF, Root.getDebugLoc(), TII->get(Opcode), RegC)
.addReg(RegA, getKillRegState(KillA))
.addReg(NewVR, getKillRegState(true));
InsInstrs.push_back(MIB2);
// Record old instructions for deletion.
DelInstrs.push_back(&Prev);
DelInstrs.push_back(&Root);
}
void PPCInstrInfo::genAlternativeCodeSequence(
MachineInstr &Root,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstIdxForVirtReg) const {
MachineRegisterInfo &MRI = Root.getParent()->getParent()->getRegInfo();
// Select the previous instruction in the sequence based on the input pattern.
MachineInstr *Prev = nullptr;
switch (Pattern) {
case MachineCombinerPattern::MC_REASSOC_AX_BY:
case MachineCombinerPattern::MC_REASSOC_XA_BY:
Prev = MRI.getUniqueVRegDef(Root.getOperand(1).getReg());
break;
case MachineCombinerPattern::MC_REASSOC_AX_YB:
case MachineCombinerPattern::MC_REASSOC_XA_YB:
Prev = MRI.getUniqueVRegDef(Root.getOperand(2).getReg());
}
assert(Prev && "Unknown pattern for machine combiner");
reassociateOps(Root, *Prev, Pattern, InsInstrs, DelInstrs, InstIdxForVirtReg);
return;
return TargetInstrInfo::getMachineCombinerPatterns(Root, Patterns);
}
// Detect 32 -> 64-bit extensions where we may reuse the low sub-register.

21
lib/Target/PowerPC/PPCInstrInfo.h
View File

@ -63,19 +63,6 @@ enum PPC970_Unit {
};
} // end namespace PPCII
namespace MachineCombinerPattern {
enum MC_PATTERN : int {
// These are commutative variants for reassociating a computation chain
// of the form:
// B = A op X (Prev)
// C = B op Y (Root)
MC_REASSOC_AX_BY = 0,
MC_REASSOC_AX_YB = 1,
MC_REASSOC_XA_BY = 2,
MC_REASSOC_XA_YB = 3,
};
} // end namespace MachineCombinerPattern
class PPCSubtarget;
class PPCInstrInfo : public PPCGenInstrInfo {
PPCSubtarget &Subtarget;
@ -143,13 +130,7 @@ public:
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &P) const override;
/// When getMachineCombinerPatterns() finds a pattern, this function generates
/// the instructions that could replace the original code sequence.
void genAlternativeCodeSequence(
MachineInstr &Root, MachineCombinerPattern::MC_PATTERN P,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const override;
bool isAssociativeAndCommutative(const MachineInstr &Inst) const override;
bool isCoalescableExtInstr(const MachineInstr &MI,
unsigned &SrcReg, unsigned &DstReg,

213
lib/Target/X86/X86InstrInfo.cpp
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@ -6328,13 +6328,10 @@ hasHighOperandLatency(const TargetSchedModel &SchedModel,
return isHighLatencyDef(DefMI->getOpcode());
}
static bool hasReassociableOperands(const MachineInstr &Inst,
const MachineBasicBlock *MBB) {
bool X86InstrInfo::hasReassociableOperands(const MachineInstr &Inst,
const MachineBasicBlock *MBB) const {
assert((Inst.getNumOperands() == 3 || Inst.getNumOperands() == 4) &&
"Reassociation needs binary operators");
const MachineOperand &Op1 = Inst.getOperand(1);
const MachineOperand &Op2 = Inst.getOperand(2);
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
// Integer binary math/logic instructions have a third source operand:
// the EFLAGS register. That operand must be both defined here and never
@ -6350,52 +6347,14 @@ static bool hasReassociableOperands(const MachineInstr &Inst,
return false;
}
// We need virtual register definitions for the operands that we will
// reassociate.
MachineInstr *MI1 = nullptr;
MachineInstr *MI2 = nullptr;
if (Op1.isReg() && TargetRegisterInfo::isVirtualRegister(Op1.getReg()))
MI1 = MRI.getUniqueVRegDef(Op1.getReg());
if (Op2.isReg() && TargetRegisterInfo::isVirtualRegister(Op2.getReg()))
MI2 = MRI.getUniqueVRegDef(Op2.getReg());
// And they need to be in the trace (otherwise, they won't have a depth).
if (MI1 && MI2 && MI1->getParent() == MBB && MI2->getParent() == MBB)
return true;
return false;
}
static bool hasReassociableSibling(const MachineInstr &Inst, bool &Commuted) {
const MachineBasicBlock *MBB = Inst.getParent();
const MachineRegisterInfo &MRI = MBB->getParent()->getRegInfo();
MachineInstr *MI1 = MRI.getUniqueVRegDef(Inst.getOperand(1).getReg());
MachineInstr *MI2 = MRI.getUniqueVRegDef(Inst.getOperand(2).getReg());
unsigned AssocOpcode = Inst.getOpcode();
// If only one operand has the same opcode and it's the second source operand,
// the operands must be commuted.
Commuted = MI1->getOpcode() != AssocOpcode && MI2->getOpcode() == AssocOpcode;
if (Commuted)
std::swap(MI1, MI2);
// 1. The previous instruction must be the same type as Inst.
// 2. The previous instruction must have virtual register definitions for its
// operands in the same basic block as Inst.
// 3. The previous instruction's result must only be used by Inst.
if (MI1->getOpcode() == AssocOpcode &&
hasReassociableOperands(*MI1, MBB) &&
MRI.hasOneNonDBGUse(MI1->getOperand(0).getReg()))
return true;
return false;
return TargetInstrInfo::hasReassociableOperands(Inst, MBB);
}
// TODO: There are many more machine instruction opcodes to match:
// 1. Other data types (integer, vectors)
// 2. Other math / logic operations (xor, or)
// 3. Other forms of the same operation (intrinsics and other variants)
static bool isAssociativeAndCommutative(const MachineInstr &Inst) {
bool X86InstrInfo::isAssociativeAndCommutative(const MachineInstr &Inst) const {
switch (Inst.getOpcode()) {
case X86::AND8rr:
case X86::AND16rr:
@ -6468,63 +6427,12 @@ static bool isAssociativeAndCommutative(const MachineInstr &Inst) {
}
}
/// Return true if the input instruction is part of a chain of dependent ops
/// that are suitable for reassociation, otherwise return false.
/// If the instruction's operands must be commuted to have a previous
/// instruction of the same type define the first source operand, Commuted will
/// be set to true.
static bool isReassociationCandidate(const MachineInstr &Inst, bool &Commuted) {
// 1. The operation must be associative and commutative.
// 2. The instruction must have virtual register definitions for its
// operands in the same basic block.
// 3. The instruction must have a reassociable sibling.
if (isAssociativeAndCommutative(Inst) &&
hasReassociableOperands(Inst, Inst.getParent()) &&
hasReassociableSibling(Inst, Commuted))
return true;
return false;
}
// FIXME: This has the potential to be expensive (compile time) while not
// improving the code at all. Some ways to limit the overhead:
// 1. Track successful transforms; bail out if hit rate gets too low.
// 2. Only enable at -O3 or some other non-default optimization level.
// 3. Pre-screen pattern candidates here: if an operand of the previous
// instruction is known to not increase the critical path, then don't match
// that pattern.
bool X86InstrInfo::getMachineCombinerPatterns(MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &Patterns) const {
// TODO: There is nothing x86-specific here except the instruction type.
// This logic could be hoisted into the machine combiner pass itself.
// Look for this reassociation pattern:
// B = A op X (Prev)
// C = B op Y (Root)
bool Commute;
if (isReassociationCandidate(Root, Commute)) {
// We found a sequence of instructions that may be suitable for a
// reassociation of operands to increase ILP. Specify each commutation
// possibility for the Prev instruction in the sequence and let the
// machine combiner decide if changing the operands is worthwhile.
if (Commute) {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_YB);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_YB);
} else {
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_AX_BY);
Patterns.push_back(MachineCombinerPattern::MC_REASSOC_XA_BY);
}
return true;
}
return false;
}
/// This is an architecture-specific helper function of reassociateOps.
/// Set special operand attributes for new instructions after reassociation.
static void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,
MachineInstr &NewMI1, MachineInstr &NewMI2) {
void X86InstrInfo::setSpecialOperandAttr(MachineInstr &OldMI1,
MachineInstr &OldMI2,
MachineInstr &NewMI1,
MachineInstr &NewMI2) const {
// Integer instructions define an implicit EFLAGS source register operand as
// the third source (fourth total) operand.
if (OldMI1.getNumOperands() != 4 || OldMI2.getNumOperands() != 4)
@ -6559,111 +6467,6 @@ static void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,
NewOp2.setIsDead();
}
/// Attempt the following reassociation to reduce critical path length:
/// B = A op X (Prev)
/// C = B op Y (Root)
/// ===>
/// B = X op Y
/// C = A op B
static void reassociateOps(MachineInstr &Root, MachineInstr &Prev,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) {
MachineFunction *MF = Root.getParent()->getParent();
MachineRegisterInfo &MRI = MF->getRegInfo();
const TargetInstrInfo *TII = MF->getSubtarget().getInstrInfo();
const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
const TargetRegisterClass *RC = Root.getRegClassConstraint(0, TII, TRI);
// This array encodes the operand index for each parameter because the
// operands may be commuted. Each row corresponds to a pattern value,
// and each column specifies the index of A, B, X, Y.
unsigned OpIdx[4][4] = {
{ 1, 1, 2, 2 },
{ 1, 2, 2, 1 },
{ 2, 1, 1, 2 },
{ 2, 2, 1, 1 }
};
MachineOperand &OpA = Prev.getOperand(OpIdx[Pattern][0]);
MachineOperand &OpB = Root.getOperand(OpIdx[Pattern][1]);
MachineOperand &OpX = Prev.getOperand(OpIdx[Pattern][2]);
MachineOperand &OpY = Root.getOperand(OpIdx[Pattern][3]);
MachineOperand &OpC = Root.getOperand(0);
unsigned RegA = OpA.getReg();
unsigned RegB = OpB.getReg();
unsigned RegX = OpX.getReg();
unsigned RegY = OpY.getReg();
unsigned RegC = OpC.getReg();
if (TargetRegisterInfo::isVirtualRegister(RegA))
MRI.constrainRegClass(RegA, RC);
if (TargetRegisterInfo::isVirtualRegister(RegB))
MRI.constrainRegClass(RegB, RC);
if (TargetRegisterInfo::isVirtualRegister(RegX))
MRI.constrainRegClass(RegX, RC);
if (TargetRegisterInfo::isVirtualRegister(RegY))
MRI.constrainRegClass(RegY, RC);
if (TargetRegisterInfo::isVirtualRegister(RegC))
MRI.constrainRegClass(RegC, RC);
// Create a new virtual register for the result of (X op Y) instead of
// recycling RegB because the MachineCombiner's computation of the critical
// path requires a new register definition rather than an existing one.
unsigned NewVR = MRI.createVirtualRegister(RC);
InstrIdxForVirtReg.insert(std::make_pair(NewVR, 0));
unsigned Opcode = Root.getOpcode();
bool KillA = OpA.isKill();
bool KillX = OpX.isKill();
bool KillY = OpY.isKill();
// Create new instructions for insertion.
MachineInstrBuilder MIB1 =
BuildMI(*MF, Prev.getDebugLoc(), TII->get(Opcode), NewVR)
.addReg(RegX, getKillRegState(KillX))
.addReg(RegY, getKillRegState(KillY));
MachineInstrBuilder MIB2 =
BuildMI(*MF, Root.getDebugLoc(), TII->get(Opcode), RegC)
.addReg(RegA, getKillRegState(KillA))
.addReg(NewVR, getKillRegState(true));
setSpecialOperandAttr(Root, Prev, *MIB1, *MIB2);
// Record new instructions for insertion and old instructions for deletion.
InsInstrs.push_back(MIB1);
InsInstrs.push_back(MIB2);
DelInstrs.push_back(&Prev);
DelInstrs.push_back(&Root);
}
void X86InstrInfo::genAlternativeCodeSequence(
MachineInstr &Root,
MachineCombinerPattern::MC_PATTERN Pattern,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstIdxForVirtReg) const {
MachineRegisterInfo &MRI = Root.getParent()->getParent()->getRegInfo();
// Select the previous instruction in the sequence based on the input pattern.
MachineInstr *Prev = nullptr;
switch (Pattern) {
case MachineCombinerPattern::MC_REASSOC_AX_BY:
case MachineCombinerPattern::MC_REASSOC_XA_BY:
Prev = MRI.getUniqueVRegDef(Root.getOperand(1).getReg());
break;
case MachineCombinerPattern::MC_REASSOC_AX_YB:
case MachineCombinerPattern::MC_REASSOC_XA_YB:
Prev = MRI.getUniqueVRegDef(Root.getOperand(2).getReg());
}
assert(Prev && "Unknown pattern for machine combiner");
reassociateOps(Root, *Prev, Pattern, InsInstrs, DelInstrs, InstIdxForVirtReg);
return;
}
std::pair<unsigned, unsigned>
X86InstrInfo::decomposeMachineOperandsTargetFlags(unsigned TF) const {
return std::make_pair(TF, 0u);

34
lib/Target/X86/X86InstrInfo.h
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@ -26,19 +26,6 @@ namespace llvm {
class X86RegisterInfo;
class X86Subtarget;
namespace MachineCombinerPattern {
enum MC_PATTERN : int {
// These are commutative variants for reassociating a computation chain
// of the form:
// B = A op X (Prev)
// C = B op Y (Root)
MC_REASSOC_AX_BY = 0,
MC_REASSOC_AX_YB = 1,
MC_REASSOC_XA_BY = 2,
MC_REASSOC_XA_YB = 3,
};
} // end namespace MachineCombinerPattern
namespace X86 {
// X86 specific condition code. These correspond to X86_*_COND in
// X86InstrInfo.td. They must be kept in synch.
@ -452,25 +439,18 @@ public:
const MachineInstr *UseMI,
unsigned UseIdx) const override;
bool useMachineCombiner() const override {
return true;
}
/// Return true when there is potentially a faster code sequence
/// for an instruction chain ending in <Root>. All potential patterns are
/// output in the <Pattern> array.
bool getMachineCombinerPatterns(
MachineInstr &Root,
SmallVectorImpl<MachineCombinerPattern::MC_PATTERN> &P) const override;
bool isAssociativeAndCommutative(const MachineInstr &Inst) const override;
/// When getMachineCombinerPatterns() finds a pattern, this function generates
/// the instructions that could replace the original code sequence.
void genAlternativeCodeSequence(
MachineInstr &Root, MachineCombinerPattern::MC_PATTERN P,
SmallVectorImpl<MachineInstr *> &InsInstrs,
SmallVectorImpl<MachineInstr *> &DelInstrs,
DenseMap<unsigned, unsigned> &InstrIdxForVirtReg) const override;
bool hasReassociableOperands(const MachineInstr &Inst,
const MachineBasicBlock *MBB) const override;
void setSpecialOperandAttr(MachineInstr &OldMI1, MachineInstr &OldMI2,
MachineInstr &NewMI1,
MachineInstr &NewMI2) const override;
/// analyzeCompare - For a comparison instruction, return the source registers
/// in SrcReg and SrcReg2 if having two register operands, and the value it