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diff --git a/llvm/lib/Target/X86/X86CallFrameOptimization.cpp b/llvm/lib/Target/X86/X86CallFrameOptimization.cpp
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+//===----- X86CallFrameOptimization.cpp - Optimize x86 call sequences -----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines a pass that optimizes call sequences on x86.
+// Currently, it converts movs of function parameters onto the stack into
+// pushes. This is beneficial for two main reasons:
+// 1) The push instruction encoding is much smaller than a stack-ptr-based mov.
+// 2) It is possible to push memory arguments directly. So, if the
+// the transformation is performed pre-reg-alloc, it can help relieve
+// register pressure.
+//
+//===----------------------------------------------------------------------===//
+
+#include "MCTargetDesc/X86BaseInfo.h"
+#include "X86FrameLowering.h"
+#include "X86InstrInfo.h"
+#include "X86MachineFunctionInfo.h"
+#include "X86RegisterInfo.h"
+#include "X86Subtarget.h"
+#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineFunctionPass.h"
+#include "llvm/CodeGen/MachineInstr.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineOperand.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/TargetInstrInfo.h"
+#include "llvm/CodeGen/TargetRegisterInfo.h"
+#include "llvm/IR/DebugLoc.h"
+#include "llvm/IR/Function.h"
+#include "llvm/MC/MCDwarf.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MathExtras.h"
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+
+using namespace llvm;
+
+#define DEBUG_TYPE "x86-cf-opt"
+
+static cl::opt<bool>
+ NoX86CFOpt("no-x86-call-frame-opt",
+ cl::desc("Avoid optimizing x86 call frames for size"),
+ cl::init(false), cl::Hidden);
+
+namespace {
+
+class X86CallFrameOptimization : public MachineFunctionPass {
+public:
+ X86CallFrameOptimization() : MachineFunctionPass(ID) { }
+
+ bool runOnMachineFunction(MachineFunction &MF) override;
+
+ static char ID;
+
+private:
+ // Information we know about a particular call site
+ struct CallContext {
+ CallContext() : FrameSetup(nullptr), ArgStoreVector(4, nullptr) {}
+
+ // Iterator referring to the frame setup instruction
+ MachineBasicBlock::iterator FrameSetup;
+
+ // Actual call instruction
+ MachineInstr *Call = nullptr;
+
+ // A copy of the stack pointer
+ MachineInstr *SPCopy = nullptr;
+
+ // The total displacement of all passed parameters
+ int64_t ExpectedDist = 0;
+
+ // The sequence of storing instructions used to pass the parameters
+ SmallVector<MachineInstr *, 4> ArgStoreVector;
+
+ // True if this call site has no stack parameters
+ bool NoStackParams = false;
+
+ // True if this call site can use push instructions
+ bool UsePush = false;
+ };
+
+ typedef SmallVector<CallContext, 8> ContextVector;
+
+ bool isLegal(MachineFunction &MF);
+
+ bool isProfitable(MachineFunction &MF, ContextVector &CallSeqMap);
+
+ void collectCallInfo(MachineFunction &MF, MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator I, CallContext &Context);
+
+ void adjustCallSequence(MachineFunction &MF, const CallContext &Context);
+
+ MachineInstr *canFoldIntoRegPush(MachineBasicBlock::iterator FrameSetup,
+ unsigned Reg);
+
+ enum InstClassification { Convert, Skip, Exit };
+
+ InstClassification classifyInstruction(MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator MI,
+ const X86RegisterInfo &RegInfo,
+ DenseSet<unsigned int> &UsedRegs);
+
+ StringRef getPassName() const override { return "X86 Optimize Call Frame"; }
+
+ const X86InstrInfo *TII;
+ const X86FrameLowering *TFL;
+ const X86Subtarget *STI;
+ MachineRegisterInfo *MRI;
+ unsigned SlotSize;
+ unsigned Log2SlotSize;
+};
+
+} // end anonymous namespace
+char X86CallFrameOptimization::ID = 0;
+INITIALIZE_PASS(X86CallFrameOptimization, DEBUG_TYPE,
+ "X86 Call Frame Optimization", false, false)
+
+// This checks whether the transformation is legal.
+// Also returns false in cases where it's potentially legal, but
+// we don't even want to try.
+bool X86CallFrameOptimization::isLegal(MachineFunction &MF) {
+ if (NoX86CFOpt.getValue())
+ return false;
+
+ // We can't encode multiple DW_CFA_GNU_args_size or DW_CFA_def_cfa_offset
+ // in the compact unwind encoding that Darwin uses. So, bail if there
+ // is a danger of that being generated.
+ if (STI->isTargetDarwin() &&
+ (!MF.getLandingPads().empty() ||
+ (MF.getFunction().needsUnwindTableEntry() && !TFL->hasFP(MF))))
+ return false;
+
+ // It is not valid to change the stack pointer outside the prolog/epilog
+ // on 64-bit Windows.
+ if (STI->isTargetWin64())
+ return false;
+
+ // You would expect straight-line code between call-frame setup and
+ // call-frame destroy. You would be wrong. There are circumstances (e.g.
+ // CMOV_GR8 expansion of a select that feeds a function call!) where we can
+ // end up with the setup and the destroy in different basic blocks.
+ // This is bad, and breaks SP adjustment.
+ // So, check that all of the frames in the function are closed inside
+ // the same block, and, for good measure, that there are no nested frames.
+ //
+ // If any call allocates more argument stack memory than the stack
+ // probe size, don't do this optimization. Otherwise, this pass
+ // would need to synthesize additional stack probe calls to allocate
+ // memory for arguments.
+ unsigned FrameSetupOpcode = TII->getCallFrameSetupOpcode();
+ unsigned FrameDestroyOpcode = TII->getCallFrameDestroyOpcode();
+ bool UseStackProbe =
+ !STI->getTargetLowering()->getStackProbeSymbolName(MF).empty();
+ unsigned StackProbeSize = STI->getTargetLowering()->getStackProbeSize(MF);
+ for (MachineBasicBlock &BB : MF) {
+ bool InsideFrameSequence = false;
+ for (MachineInstr &MI : BB) {
+ if (MI.getOpcode() == FrameSetupOpcode) {
+ if (TII->getFrameSize(MI) >= StackProbeSize && UseStackProbe)
+ return false;
+ if (InsideFrameSequence)
+ return false;
+ InsideFrameSequence = true;
+ } else if (MI.getOpcode() == FrameDestroyOpcode) {
+ if (!InsideFrameSequence)
+ return false;
+ InsideFrameSequence = false;
+ }
+ }
+
+ if (InsideFrameSequence)
+ return false;
+ }
+
+ return true;
+}
+
+// Check whether this transformation is profitable for a particular
+// function - in terms of code size.
+bool X86CallFrameOptimization::isProfitable(MachineFunction &MF,
+ ContextVector &CallSeqVector) {
+ // This transformation is always a win when we do not expect to have
+ // a reserved call frame. Under other circumstances, it may be either
+ // a win or a loss, and requires a heuristic.
+ bool CannotReserveFrame = MF.getFrameInfo().hasVarSizedObjects();
+ if (CannotReserveFrame)
+ return true;
+
+ unsigned StackAlign = TFL->getStackAlignment();
+
+ int64_t Advantage = 0;
+ for (auto CC : CallSeqVector) {
+ // Call sites where no parameters are passed on the stack
+ // do not affect the cost, since there needs to be no
+ // stack adjustment.
+ if (CC.NoStackParams)
+ continue;
+
+ if (!CC.UsePush) {
+ // If we don't use pushes for a particular call site,
+ // we pay for not having a reserved call frame with an
+ // additional sub/add esp pair. The cost is ~3 bytes per instruction,
+ // depending on the size of the constant.
+ // TODO: Callee-pop functions should have a smaller penalty, because
+ // an add is needed even with a reserved call frame.
+ Advantage -= 6;
+ } else {
+ // We can use pushes. First, account for the fixed costs.
+ // We'll need a add after the call.
+ Advantage -= 3;
+ // If we have to realign the stack, we'll also need a sub before
+ if (CC.ExpectedDist % StackAlign)
+ Advantage -= 3;
+ // Now, for each push, we save ~3 bytes. For small constants, we actually,
+ // save more (up to 5 bytes), but 3 should be a good approximation.
+ Advantage += (CC.ExpectedDist >> Log2SlotSize) * 3;
+ }
+ }
+
+ return Advantage >= 0;
+}
+
+bool X86CallFrameOptimization::runOnMachineFunction(MachineFunction &MF) {
+ STI = &MF.getSubtarget<X86Subtarget>();
+ TII = STI->getInstrInfo();
+ TFL = STI->getFrameLowering();
+ MRI = &MF.getRegInfo();
+
+ const X86RegisterInfo &RegInfo =
+ *static_cast<const X86RegisterInfo *>(STI->getRegisterInfo());
+ SlotSize = RegInfo.getSlotSize();
+ assert(isPowerOf2_32(SlotSize) && "Expect power of 2 stack slot size");
+ Log2SlotSize = Log2_32(SlotSize);
+
+ if (skipFunction(MF.getFunction()) || !isLegal(MF))
+ return false;
+
+ unsigned FrameSetupOpcode = TII->getCallFrameSetupOpcode();
+
+ bool Changed = false;
+
+ ContextVector CallSeqVector;
+
+ for (auto &MBB : MF)
+ for (auto &MI : MBB)
+ if (MI.getOpcode() == FrameSetupOpcode) {
+ CallContext Context;
+ collectCallInfo(MF, MBB, MI, Context);
+ CallSeqVector.push_back(Context);
+ }
+
+ if (!isProfitable(MF, CallSeqVector))
+ return false;
+
+ for (auto CC : CallSeqVector) {
+ if (CC.UsePush) {
+ adjustCallSequence(MF, CC);
+ Changed = true;
+ }
+ }
+
+ return Changed;
+}
+
+X86CallFrameOptimization::InstClassification
+X86CallFrameOptimization::classifyInstruction(
+ MachineBasicBlock &MBB, MachineBasicBlock::iterator MI,
+ const X86RegisterInfo &RegInfo, DenseSet<unsigned int> &UsedRegs) {
+ if (MI == MBB.end())
+ return Exit;
+
+ // The instructions we actually care about are movs onto the stack or special
+ // cases of constant-stores to stack
+ switch (MI->getOpcode()) {
+ case X86::AND16mi8:
+ case X86::AND32mi8:
+ case X86::AND64mi8: {
+ MachineOperand ImmOp = MI->getOperand(X86::AddrNumOperands);
+ return ImmOp.getImm() == 0 ? Convert : Exit;
+ }
+ case X86::OR16mi8:
+ case X86::OR32mi8:
+ case X86::OR64mi8: {
+ MachineOperand ImmOp = MI->getOperand(X86::AddrNumOperands);
+ return ImmOp.getImm() == -1 ? Convert : Exit;
+ }
+ case X86::MOV32mi:
+ case X86::MOV32mr:
+ case X86::MOV64mi32:
+ case X86::MOV64mr:
+ return Convert;
+ }
+
+ // Not all calling conventions have only stack MOVs between the stack
+ // adjust and the call.
+
+ // We want to tolerate other instructions, to cover more cases.
+ // In particular:
+ // a) PCrel calls, where we expect an additional COPY of the basereg.
+ // b) Passing frame-index addresses.
+ // c) Calling conventions that have inreg parameters. These generate
+ // both copies and movs into registers.
+ // To avoid creating lots of special cases, allow any instruction
+ // that does not write into memory, does not def or use the stack
+ // pointer, and does not def any register that was used by a preceding
+ // push.
+ // (Reading from memory is allowed, even if referenced through a
+ // frame index, since these will get adjusted properly in PEI)
+
+ // The reason for the last condition is that the pushes can't replace
+ // the movs in place, because the order must be reversed.
+ // So if we have a MOV32mr that uses EDX, then an instruction that defs
+ // EDX, and then the call, after the transformation the push will use
+ // the modified version of EDX, and not the original one.
+ // Since we are still in SSA form at this point, we only need to
+ // make sure we don't clobber any *physical* registers that were
+ // used by an earlier mov that will become a push.
+
+ if (MI->isCall() || MI->mayStore())
+ return Exit;
+
+ for (const MachineOperand &MO : MI->operands()) {
+ if (!MO.isReg())
+ continue;
+ Register Reg = MO.getReg();
+ if (!Register::isPhysicalRegister(Reg))
+ continue;
+ if (RegInfo.regsOverlap(Reg, RegInfo.getStackRegister()))
+ return Exit;
+ if (MO.isDef()) {
+ for (unsigned int U : UsedRegs)
+ if (RegInfo.regsOverlap(Reg, U))
+ return Exit;
+ }
+ }
+
+ return Skip;
+}
+
+void X86CallFrameOptimization::collectCallInfo(MachineFunction &MF,
+ MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator I,
+ CallContext &Context) {
+ // Check that this particular call sequence is amenable to the
+ // transformation.
+ const X86RegisterInfo &RegInfo =
+ *static_cast<const X86RegisterInfo *>(STI->getRegisterInfo());
+
+ // We expect to enter this at the beginning of a call sequence
+ assert(I->getOpcode() == TII->getCallFrameSetupOpcode());
+ MachineBasicBlock::iterator FrameSetup = I++;
+ Context.FrameSetup = FrameSetup;
+
+ // How much do we adjust the stack? This puts an upper bound on
+ // the number of parameters actually passed on it.
+ unsigned int MaxAdjust = TII->getFrameSize(*FrameSetup) >> Log2SlotSize;
+
+ // A zero adjustment means no stack parameters
+ if (!MaxAdjust) {
+ Context.NoStackParams = true;
+ return;
+ }
+
+ // Skip over DEBUG_VALUE.
+ // For globals in PIC mode, we can have some LEAs here. Skip them as well.
+ // TODO: Extend this to something that covers more cases.
+ while (I->getOpcode() == X86::LEA32r || I->isDebugInstr())
+ ++I;
+
+ Register StackPtr = RegInfo.getStackRegister();
+ auto StackPtrCopyInst = MBB.end();
+ // SelectionDAG (but not FastISel) inserts a copy of ESP into a virtual
+ // register. If it's there, use that virtual register as stack pointer
+ // instead. Also, we need to locate this instruction so that we can later
+ // safely ignore it while doing the conservative processing of the call chain.
+ // The COPY can be located anywhere between the call-frame setup
+ // instruction and its first use. We use the call instruction as a boundary
+ // because it is usually cheaper to check if an instruction is a call than
+ // checking if an instruction uses a register.
+ for (auto J = I; !J->isCall(); ++J)
+ if (J->isCopy() && J->getOperand(0).isReg() && J->getOperand(1).isReg() &&
+ J->getOperand(1).getReg() == StackPtr) {
+ StackPtrCopyInst = J;
+ Context.SPCopy = &*J++;
+ StackPtr = Context.SPCopy->getOperand(0).getReg();
+ break;
+ }
+
+ // Scan the call setup sequence for the pattern we're looking for.
+ // We only handle a simple case - a sequence of store instructions that
+ // push a sequence of stack-slot-aligned values onto the stack, with
+ // no gaps between them.
+ if (MaxAdjust > 4)
+ Context.ArgStoreVector.resize(MaxAdjust, nullptr);
+
+ DenseSet<unsigned int> UsedRegs;
+
+ for (InstClassification Classification = Skip; Classification != Exit; ++I) {
+ // If this is the COPY of the stack pointer, it's ok to ignore.
+ if (I == StackPtrCopyInst)
+ continue;
+ Classification = classifyInstruction(MBB, I, RegInfo, UsedRegs);
+ if (Classification != Convert)
+ continue;
+ // We know the instruction has a supported store opcode.
+ // We only want movs of the form:
+ // mov imm/reg, k(%StackPtr)
+ // If we run into something else, bail.
+ // Note that AddrBaseReg may, counter to its name, not be a register,
+ // but rather a frame index.
+ // TODO: Support the fi case. This should probably work now that we
+ // have the infrastructure to track the stack pointer within a call
+ // sequence.
+ if (!I->getOperand(X86::AddrBaseReg).isReg() ||
+ (I->getOperand(X86::AddrBaseReg).getReg() != StackPtr) ||
+ !I->getOperand(X86::AddrScaleAmt).isImm() ||
+ (I->getOperand(X86::AddrScaleAmt).getImm() != 1) ||
+ (I->getOperand(X86::AddrIndexReg).getReg() != X86::NoRegister) ||
+ (I->getOperand(X86::AddrSegmentReg).getReg() != X86::NoRegister) ||
+ !I->getOperand(X86::AddrDisp).isImm())
+ return;
+
+ int64_t StackDisp = I->getOperand(X86::AddrDisp).getImm();
+ assert(StackDisp >= 0 &&
+ "Negative stack displacement when passing parameters");
+
+ // We really don't want to consider the unaligned case.
+ if (StackDisp & (SlotSize - 1))
+ return;
+ StackDisp >>= Log2SlotSize;
+
+ assert((size_t)StackDisp < Context.ArgStoreVector.size() &&
+ "Function call has more parameters than the stack is adjusted for.");
+
+ // If the same stack slot is being filled twice, something's fishy.
+ if (Context.ArgStoreVector[StackDisp] != nullptr)
+ return;
+ Context.ArgStoreVector[StackDisp] = &*I;
+
+ for (const MachineOperand &MO : I->uses()) {
+ if (!MO.isReg())
+ continue;
+ Register Reg = MO.getReg();
+ if (Register::isPhysicalRegister(Reg))
+ UsedRegs.insert(Reg);
+ }
+ }
+
+ --I;
+
+ // We now expect the end of the sequence. If we stopped early,
+ // or reached the end of the block without finding a call, bail.
+ if (I == MBB.end() || !I->isCall())
+ return;
+
+ Context.Call = &*I;
+ if ((++I)->getOpcode() != TII->getCallFrameDestroyOpcode())
+ return;
+
+ // Now, go through the vector, and see that we don't have any gaps,
+ // but only a series of storing instructions.
+ auto MMI = Context.ArgStoreVector.begin(), MME = Context.ArgStoreVector.end();
+ for (; MMI != MME; ++MMI, Context.ExpectedDist += SlotSize)
+ if (*MMI == nullptr)
+ break;
+
+ // If the call had no parameters, do nothing
+ if (MMI == Context.ArgStoreVector.begin())
+ return;
+
+ // We are either at the last parameter, or a gap.
+ // Make sure it's not a gap
+ for (; MMI != MME; ++MMI)
+ if (*MMI != nullptr)
+ return;
+
+ Context.UsePush = true;
+}
+
+void X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
+ const CallContext &Context) {
+ // Ok, we can in fact do the transformation for this call.
+ // Do not remove the FrameSetup instruction, but adjust the parameters.
+ // PEI will end up finalizing the handling of this.
+ MachineBasicBlock::iterator FrameSetup = Context.FrameSetup;
+ MachineBasicBlock &MBB = *(FrameSetup->getParent());
+ TII->setFrameAdjustment(*FrameSetup, Context.ExpectedDist);
+
+ DebugLoc DL = FrameSetup->getDebugLoc();
+ bool Is64Bit = STI->is64Bit();
+ // Now, iterate through the vector in reverse order, and replace the store to
+ // stack with pushes. MOVmi/MOVmr doesn't have any defs, so no need to
+ // replace uses.
+ for (int Idx = (Context.ExpectedDist >> Log2SlotSize) - 1; Idx >= 0; --Idx) {
+ MachineBasicBlock::iterator Store = *Context.ArgStoreVector[Idx];
+ MachineOperand PushOp = Store->getOperand(X86::AddrNumOperands);
+ MachineBasicBlock::iterator Push = nullptr;
+ unsigned PushOpcode;
+ switch (Store->getOpcode()) {
+ default:
+ llvm_unreachable("Unexpected Opcode!");
+ case X86::AND16mi8:
+ case X86::AND32mi8:
+ case X86::AND64mi8:
+ case X86::OR16mi8:
+ case X86::OR32mi8:
+ case X86::OR64mi8:
+ case X86::MOV32mi:
+ case X86::MOV64mi32:
+ PushOpcode = Is64Bit ? X86::PUSH64i32 : X86::PUSHi32;
+ // If the operand is a small (8-bit) immediate, we can use a
+ // PUSH instruction with a shorter encoding.
+ // Note that isImm() may fail even though this is a MOVmi, because
+ // the operand can also be a symbol.
+ if (PushOp.isImm()) {
+ int64_t Val = PushOp.getImm();
+ if (isInt<8>(Val))
+ PushOpcode = Is64Bit ? X86::PUSH64i8 : X86::PUSH32i8;
+ }
+ Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode)).add(PushOp);
+ break;
+ case X86::MOV32mr:
+ case X86::MOV64mr: {
+ Register Reg = PushOp.getReg();
+
+ // If storing a 32-bit vreg on 64-bit targets, extend to a 64-bit vreg
+ // in preparation for the PUSH64. The upper 32 bits can be undef.
+ if (Is64Bit && Store->getOpcode() == X86::MOV32mr) {
+ Register UndefReg = MRI->createVirtualRegister(&X86::GR64RegClass);
+ Reg = MRI->createVirtualRegister(&X86::GR64RegClass);
+ BuildMI(MBB, Context.Call, DL, TII->get(X86::IMPLICIT_DEF), UndefReg);
+ BuildMI(MBB, Context.Call, DL, TII->get(X86::INSERT_SUBREG), Reg)
+ .addReg(UndefReg)
+ .add(PushOp)
+ .addImm(X86::sub_32bit);
+ }
+
+ // If PUSHrmm is not slow on this target, try to fold the source of the
+ // push into the instruction.
+ bool SlowPUSHrmm = STI->isAtom() || STI->isSLM();
+
+ // Check that this is legal to fold. Right now, we're extremely
+ // conservative about that.
+ MachineInstr *DefMov = nullptr;
+ if (!SlowPUSHrmm && (DefMov = canFoldIntoRegPush(FrameSetup, Reg))) {
+ PushOpcode = Is64Bit ? X86::PUSH64rmm : X86::PUSH32rmm;
+ Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode));
+
+ unsigned NumOps = DefMov->getDesc().getNumOperands();
+ for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)
+ Push->addOperand(DefMov->getOperand(i));
+
+ DefMov->eraseFromParent();
+ } else {
+ PushOpcode = Is64Bit ? X86::PUSH64r : X86::PUSH32r;
+ Push = BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode))
+ .addReg(Reg)
+ .getInstr();
+ }
+ break;
+ }
+ }
+
+ // For debugging, when using SP-based CFA, we need to adjust the CFA
+ // offset after each push.
+ // TODO: This is needed only if we require precise CFA.
+ if (!TFL->hasFP(MF))
+ TFL->BuildCFI(
+ MBB, std::next(Push), DL,
+ MCCFIInstruction::createAdjustCfaOffset(nullptr, SlotSize));
+
+ MBB.erase(Store);
+ }
+
+ // The stack-pointer copy is no longer used in the call sequences.
+ // There should not be any other users, but we can't commit to that, so:
+ if (Context.SPCopy && MRI->use_empty(Context.SPCopy->getOperand(0).getReg()))
+ Context.SPCopy->eraseFromParent();
+
+ // Once we've done this, we need to make sure PEI doesn't assume a reserved
+ // frame.
+ X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
+ FuncInfo->setHasPushSequences(true);
+}
+
+MachineInstr *X86CallFrameOptimization::canFoldIntoRegPush(
+ MachineBasicBlock::iterator FrameSetup, unsigned Reg) {
+ // Do an extremely restricted form of load folding.
+ // ISel will often create patterns like:
+ // movl 4(%edi), %eax
+ // movl 8(%edi), %ecx
+ // movl 12(%edi), %edx
+ // movl %edx, 8(%esp)
+ // movl %ecx, 4(%esp)
+ // movl %eax, (%esp)
+ // call
+ // Get rid of those with prejudice.
+ if (!Register::isVirtualRegister(Reg))
+ return nullptr;
+
+ // Make sure this is the only use of Reg.
+ if (!MRI->hasOneNonDBGUse(Reg))
+ return nullptr;
+
+ MachineInstr &DefMI = *MRI->getVRegDef(Reg);
+
+ // Make sure the def is a MOV from memory.
+ // If the def is in another block, give up.
+ if ((DefMI.getOpcode() != X86::MOV32rm &&
+ DefMI.getOpcode() != X86::MOV64rm) ||
+ DefMI.getParent() != FrameSetup->getParent())
+ return nullptr;
+
+ // Make sure we don't have any instructions between DefMI and the
+ // push that make folding the load illegal.
+ for (MachineBasicBlock::iterator I = DefMI; I != FrameSetup; ++I)
+ if (I->isLoadFoldBarrier())
+ return nullptr;
+
+ return &DefMI;
+}
+
+FunctionPass *llvm::createX86CallFrameOptimization() {
+ return new X86CallFrameOptimization();
+}
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