From e86aa9a8a455f90bf3d6dc567b9e39b2e4510246 Mon Sep 17 00:00:00 2001 From: Michael Kuperstein Date: Sun, 1 Feb 2015 16:15:07 +0000 Subject: Revert r227728 due to bad line endings. llvm-svn: 227746 --- llvm/lib/Target/X86/X86CallFrameOptimization.cpp | 400 ----------------------- 1 file changed, 400 deletions(-) delete mode 100644 llvm/lib/Target/X86/X86CallFrameOptimization.cpp (limited to 'llvm/lib/Target/X86/X86CallFrameOptimization.cpp') diff --git a/llvm/lib/Target/X86/X86CallFrameOptimization.cpp b/llvm/lib/Target/X86/X86CallFrameOptimization.cpp deleted file mode 100644 index f832b94..0000000 --- a/llvm/lib/Target/X86/X86CallFrameOptimization.cpp +++ /dev/null @@ -1,400 +0,0 @@ -//===----- X86CallFrameOptimization.cpp - Optimize x86 call sequences -----===// -// -// The LLVM Compiler Infrastructure -// -// This file is distributed under the University of Illinois Open Source -// License. See LICENSE.TXT for details. -// -//===----------------------------------------------------------------------===// -// -// 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 an esp-relative mov -// 2) It is possible to push memory arguments directly. So, if the -// the transformation is preformed pre-reg-alloc, it can help relieve -// register pressure. -// -//===----------------------------------------------------------------------===// - -#include - -#include "X86.h" -#include "X86InstrInfo.h" -#include "X86Subtarget.h" -#include "X86MachineFunctionInfo.h" -#include "llvm/ADT/Statistic.h" -#include "llvm/CodeGen/MachineFunctionPass.h" -#include "llvm/CodeGen/MachineInstrBuilder.h" -#include "llvm/CodeGen/MachineRegisterInfo.h" -#include "llvm/CodeGen/Passes.h" -#include "llvm/IR/Function.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Target/TargetInstrInfo.h" - -using namespace llvm; - -#define DEBUG_TYPE "x86-cf-opt" - -cl::opt 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; - -private: - bool shouldPerformTransformation(MachineFunction &MF); - - bool adjustCallSequence(MachineFunction &MF, MachineBasicBlock &MBB, - MachineBasicBlock::iterator I); - - MachineInstr *canFoldIntoRegPush(MachineBasicBlock::iterator FrameSetup, - unsigned Reg); - - const char *getPassName() const override { - return "X86 Optimize Call Frame"; - } - - const TargetInstrInfo *TII; - const TargetFrameLowering *TFL; - const MachineRegisterInfo *MRI; - static char ID; -}; - -char X86CallFrameOptimization::ID = 0; -} - -FunctionPass *llvm::createX86CallFrameOptimization() { - return new X86CallFrameOptimization(); -} - -// This checks whether the transformation is legal and profitable -bool X86CallFrameOptimization::shouldPerformTransformation(MachineFunction &MF) { - if (NoX86CFOpt.getValue()) - return false; - - // We currently only support call sequences where *all* parameters. - // are passed on the stack. - // No point in running this in 64-bit mode, since some arguments are - // passed in-register in all common calling conventions, so the pattern - // we're looking for will never match. - const X86Subtarget &STI = MF.getTarget().getSubtarget(); - if (STI.is64Bit()) - 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. - int FrameSetupOpcode = TII->getCallFrameSetupOpcode(); - int FrameDestroyOpcode = TII->getCallFrameDestroyOpcode(); - for (MachineBasicBlock &BB : MF) { - bool InsideFrameSequence = false; - for (MachineInstr &MI : BB) { - if (MI.getOpcode() == FrameSetupOpcode) { - if (InsideFrameSequence) - return false; - InsideFrameSequence = true; - } - else if (MI.getOpcode() == FrameDestroyOpcode) { - if (!InsideFrameSequence) - return false; - InsideFrameSequence = false; - } - } - - if (InsideFrameSequence) - return false; - } - - // Now that we know the transformation is legal, check if it is - // profitable. - // TODO: Add a heuristic that actually looks at the function, - // and enable this for more cases. - - // This transformation is always a win when we expected to have - // a reserved call frame. Under other circumstances, it may be either - // a win or a loss, and requires a heuristic. - // For now, enable it only for the relatively clear win cases. - bool CannotReserveFrame = MF.getFrameInfo()->hasVarSizedObjects(); - if (CannotReserveFrame) - return true; - - // For now, don't even try to evaluate the profitability when - // not optimizing for size. - AttributeSet FnAttrs = MF.getFunction()->getAttributes(); - bool OptForSize = - FnAttrs.hasAttribute(AttributeSet::FunctionIndex, - Attribute::OptimizeForSize) || - FnAttrs.hasAttribute(AttributeSet::FunctionIndex, Attribute::MinSize); - - if (!OptForSize) - return false; - - // Stack re-alignment can make this unprofitable even in terms of size. - // As mentioned above, a better heuristic is needed. For now, don't do this - // when the required alignment is above 8. (4 would be the safe choice, but - // some experimentation showed 8 is generally good). - if (TFL->getStackAlignment() > 8) - return false; - - return true; -} - -bool X86CallFrameOptimization::runOnMachineFunction(MachineFunction &MF) { - TII = MF.getSubtarget().getInstrInfo(); - TFL = MF.getSubtarget().getFrameLowering(); - MRI = &MF.getRegInfo(); - - if (!shouldPerformTransformation(MF)) - return false; - - int FrameSetupOpcode = TII->getCallFrameSetupOpcode(); - - bool Changed = false; - - for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB) - for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) - if (I->getOpcode() == FrameSetupOpcode) - Changed |= adjustCallSequence(MF, *BB, I); - - return Changed; -} - -bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF, - MachineBasicBlock &MBB, - MachineBasicBlock::iterator I) { - - // Check that this particular call sequence is amenable to the - // transformation. - const X86RegisterInfo &RegInfo = *static_cast( - MF.getSubtarget().getRegisterInfo()); - unsigned StackPtr = RegInfo.getStackRegister(); - int FrameDestroyOpcode = TII->getCallFrameDestroyOpcode(); - - // We expect to enter this at the beginning of a call sequence - assert(I->getOpcode() == TII->getCallFrameSetupOpcode()); - MachineBasicBlock::iterator FrameSetup = I++; - - - // For globals in PIC mode, we can have some LEAs here. - // Ignore them, they don't bother us. - // TODO: Extend this to something that covers more cases. - while (I->getOpcode() == X86::LEA32r) - ++I; - - // We expect a copy instruction here. - // TODO: The copy instruction is a lowering artifact. - // We should also support a copy-less version, where the stack - // pointer is used directly. - if (!I->isCopy() || !I->getOperand(0).isReg()) - return false; - MachineBasicBlock::iterator SPCopy = I++; - StackPtr = SPCopy->getOperand(0).getReg(); - - // Scan the call setup sequence for the pattern we're looking for. - // We only handle a simple case - a sequence of MOV32mi or MOV32mr - // instructions, that push a sequence of 32-bit values onto the stack, with - // no gaps between them. - SmallVector MovVector(4, nullptr); - unsigned int MaxAdjust = FrameSetup->getOperand(0).getImm() / 4; - if (MaxAdjust > 4) - MovVector.resize(MaxAdjust, nullptr); - - do { - int Opcode = I->getOpcode(); - if (Opcode != X86::MOV32mi && Opcode != X86::MOV32mr) - break; - - // We only want movs of the form: - // movl imm/r32, k(%esp) - // 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 false; - - 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 % 4) - return false; - StackDisp /= 4; - - assert((size_t)StackDisp < MovVector.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 (MovVector[StackDisp] != nullptr) - return false; - MovVector[StackDisp] = I; - - ++I; - } while (I != MBB.end()); - - // We now expect the end of the sequence - a call and a stack adjust. - if (I == MBB.end()) - return false; - - // For PCrel calls, we expect an additional COPY of the basereg. - // If we find one, skip it. - if (I->isCopy()) { - if (I->getOperand(1).getReg() == - MF.getInfo()->getGlobalBaseReg()) - ++I; - else - return false; - } - - if (!I->isCall()) - return false; - MachineBasicBlock::iterator Call = I; - if ((++I)->getOpcode() != FrameDestroyOpcode) - return false; - - // Now, go through the vector, and see that we don't have any gaps, - // but only a series of 32-bit MOVs. - - int64_t ExpectedDist = 0; - auto MMI = MovVector.begin(), MME = MovVector.end(); - for (; MMI != MME; ++MMI, ExpectedDist += 4) - if (*MMI == nullptr) - break; - - // If the call had no parameters, do nothing - if (!ExpectedDist) - return false; - - // 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 false; - - // 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. - FrameSetup->getOperand(1).setImm(ExpectedDist); - - DebugLoc DL = I->getDebugLoc(); - // Now, iterate through the vector in reverse order, and replace the movs - // with pushes. MOVmi/MOVmr doesn't have any defs, so no need to - // replace uses. - for (int Idx = (ExpectedDist / 4) - 1; Idx >= 0; --Idx) { - MachineBasicBlock::iterator MOV = *MovVector[Idx]; - MachineOperand PushOp = MOV->getOperand(X86::AddrNumOperands); - if (MOV->getOpcode() == X86::MOV32mi) { - unsigned PushOpcode = 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 = X86::PUSH32i8; - } - BuildMI(MBB, Call, DL, TII->get(PushOpcode)).addOperand(PushOp); - } else { - unsigned int Reg = PushOp.getReg(); - - // If PUSHrmm is not slow on this target, try to fold the source of the - // push into the instruction. - const X86Subtarget &ST = MF.getTarget().getSubtarget(); - bool SlowPUSHrmm = ST.isAtom() || ST.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))) { - MachineInstr *Push = BuildMI(MBB, Call, DL, TII->get(X86::PUSH32rmm)); - - unsigned NumOps = DefMov->getDesc().getNumOperands(); - for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i) - Push->addOperand(DefMov->getOperand(i)); - - DefMov->eraseFromParent(); - } else { - BuildMI(MBB, Call, DL, TII->get(X86::PUSH32r)).addReg(Reg).getInstr(); - } - } - - MBB.erase(MOV); - } - - // 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 (MRI->use_empty(SPCopy->getOperand(0).getReg())) - SPCopy->eraseFromParent(); - - // Once we've done this, we need to make sure PEI doesn't assume a reserved - // frame. - X86MachineFunctionInfo *FuncInfo = MF.getInfo(); - FuncInfo->setHasPushSequences(true); - - return 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 (!TargetRegisterInfo::isVirtualRegister(Reg)) - return nullptr; - - // Make sure this is the only use of Reg. - if (!MRI->hasOneNonDBGUse(Reg)) - return nullptr; - - MachineBasicBlock::iterator DefMI = MRI->getVRegDef(Reg); - - // Make sure the def is a MOV from memory. - // If the def is an another block, give up. - if (DefMI->getOpcode() != X86::MOV32rm || - DefMI->getParent() != FrameSetup->getParent()) - return nullptr; - - // Be careful with movs that load from a stack slot, since it may get - // resolved incorrectly. - // TODO: Again, we already have the infrastructure, so this should work. - if (!DefMI->getOperand(1).isReg()) - return nullptr; - - // Now, make sure everything else up until the ADJCALLSTACK is a sequence - // of MOVs. To be less conservative would require duplicating a lot of the - // logic from PeepholeOptimizer. - // FIXME: A possibly better approach would be to teach the PeepholeOptimizer - // to be smarter about folding into pushes. - for (auto I = DefMI; I != FrameSetup; ++I) - if (I->getOpcode() != X86::MOV32rm) - return nullptr; - - return DefMI; -} -- cgit v1.1