//===----------------------------------------------------------------------===//
//
// This file defines a pass that optimizes call sequences on x86.
-// Currently, it converts movs of function parameters onto the stack into
+// 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
private:
bool shouldPerformTransformation(MachineFunction &MF);
- bool adjustCallSequence(MachineFunction &MF, MachineBasicBlock &MBB,
- MachineBasicBlock::iterator I);
+ // Information we know about a particular call site
+ struct CallContext {
+ CallContext()
+ : Call(nullptr), SPCopy(nullptr), ExpectedDist(0),
+ MovVector(4, nullptr), UsePush(false){};
+
+ // Actuall call instruction
+ MachineInstr *Call;
+
+ // A copy of the stack pointer
+ MachineInstr *SPCopy;
+
+ // The total displacement of all passed parameters
+ int64_t ExpectedDist;
+
+ // The sequence of movs used to pass the parameters
+ SmallVector<MachineInstr *, 4> MovVector;
+
+ // Whether this site should use push instructions
+ bool UsePush;
+ };
+
+ void collectCallInfo(MachineFunction &MF, MachineBasicBlock &MBB,
+ MachineBasicBlock::iterator I, CallContext &Context);
+
+ bool adjustCallSequence(MachineFunction &MF, MachineBasicBlock::iterator I,
+ const CallContext &Context);
MachineInstr *canFoldIntoRegPush(MachineBasicBlock::iterator FrameSetup,
unsigned Reg);
- const char *getPassName() const override {
- return "X86 Optimize Call Frame";
- }
+ const char *getPassName() const override { return "X86 Optimize Call Frame"; }
const TargetInstrInfo *TII;
const TargetFrameLowering *TFL;
}
// This checks whether the transformation is legal and profitable
-bool X86CallFrameOptimization::shouldPerformTransformation(MachineFunction &MF) {
+bool X86CallFrameOptimization::shouldPerformTransformation(
+ MachineFunction &MF) {
if (NoX86CFOpt.getValue())
return false;
if (InsideFrameSequence)
return false;
InsideFrameSequence = true;
- }
- else if (MI.getOpcode() == FrameDestroyOpcode) {
+ } else if (MI.getOpcode() == FrameDestroyOpcode) {
if (!InsideFrameSequence)
return false;
InsideFrameSequence = false;
// 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 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();
// not optimizing for size.
AttributeSet FnAttrs = MF.getFunction()->getAttributes();
bool OptForSize =
- FnAttrs.hasAttribute(AttributeSet::FunctionIndex,
- Attribute::OptimizeForSize) ||
- FnAttrs.hasAttribute(AttributeSet::FunctionIndex, Attribute::MinSize);
+ FnAttrs.hasAttribute(AttributeSet::FunctionIndex,
+ Attribute::OptimizeForSize) ||
+ FnAttrs.hasAttribute(AttributeSet::FunctionIndex, Attribute::MinSize);
if (!OptForSize)
return false;
bool Changed = false;
+ DenseMap<MachineInstr *, CallContext> CallSeqMap;
+
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);
+ if (I->getOpcode() == FrameSetupOpcode) {
+ CallContext &Context = CallSeqMap[I];
+ collectCallInfo(MF, *BB, I, Context);
+ }
+
+ for (auto CC : CallSeqMap)
+ if (CC.second.UsePush)
+ Changed |= adjustCallSequence(MF, CC.first, CC.second);
return Changed;
}
-bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
- MachineBasicBlock &MBB,
- MachineBasicBlock::iterator I) {
-
+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 *>(
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();
+ return;
+ Context.SPCopy = I++;
+ StackPtr = Context.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<MachineInstr*, 4> MovVector(4, nullptr);
unsigned int MaxAdjust = FrameSetup->getOperand(0).getImm() / 4;
if (MaxAdjust > 4)
- MovVector.resize(MaxAdjust, nullptr);
+ Context.MovVector.resize(MaxAdjust, nullptr);
do {
int Opcode = I->getOpcode();
(I->getOperand(X86::AddrIndexReg).getReg() != X86::NoRegister) ||
(I->getOperand(X86::AddrSegmentReg).getReg() != X86::NoRegister) ||
!I->getOperand(X86::AddrDisp).isImm())
- return false;
+ return;
int64_t StackDisp = I->getOperand(X86::AddrDisp).getImm();
- assert(StackDisp >= 0 && "Negative stack displacement when passing parameters");
+ assert(StackDisp >= 0 &&
+ "Negative stack displacement when passing parameters");
// We really don't want to consider the unaligned case.
if (StackDisp % 4)
- return false;
+ return;
StackDisp /= 4;
- assert((size_t)StackDisp < MovVector.size() &&
- "Function call has more parameters than the stack is adjusted for.");
+ assert((size_t)StackDisp < Context.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;
+ if (Context.MovVector[StackDisp] != nullptr)
+ return;
+ Context.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;
+ return;
// 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<X86MachineFunctionInfo>()->getGlobalBaseReg())
+ MF.getInfo<X86MachineFunctionInfo>()->getGlobalBaseReg())
++I;
else
- return false;
+ return;
}
if (!I->isCall())
- return false;
- MachineBasicBlock::iterator Call = I;
+ return;
+
+ Context.Call = I;
if ((++I)->getOpcode() != FrameDestroyOpcode)
- return false;
+ return;
// 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)
+ auto MMI = Context.MovVector.begin(), MME = Context.MovVector.end();
+ for (; MMI != MME; ++MMI, Context.ExpectedDist += 4)
if (*MMI == nullptr)
break;
-
+
// If the call had no parameters, do nothing
- if (!ExpectedDist)
- return false;
+ if (MMI == Context.MovVector.begin())
+ return;
- // We are either at the last parameter, or a gap.
+ // 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;
+ return;
+ Context.UsePush = true;
+ return;
+}
+
+bool X86CallFrameOptimization::adjustCallSequence(MachineFunction &MF,
+ MachineBasicBlock::iterator I,
+ 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.
- FrameSetup->getOperand(1).setImm(ExpectedDist);
+ MachineBasicBlock::iterator FrameSetup = I;
+ MachineBasicBlock &MBB = *(I->getParent());
+ FrameSetup->getOperand(1).setImm(Context.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
+ // 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];
+ for (int Idx = (Context.ExpectedDist / 4) - 1; Idx >= 0; --Idx) {
+ MachineBasicBlock::iterator MOV = *Context.MovVector[Idx];
MachineOperand PushOp = MOV->getOperand(X86::AddrNumOperands);
if (MOV->getOpcode() == X86::MOV32mi) {
unsigned PushOpcode = X86::PUSHi32;
if (isInt<8>(Val))
PushOpcode = X86::PUSH32i8;
}
- BuildMI(MBB, Call, DL, TII->get(PushOpcode)).addOperand(PushOp);
+ BuildMI(MBB, Context.Call, DL, TII->get(PushOpcode)).addOperand(PushOp);
} else {
unsigned int Reg = PushOp.getReg();
// conservative about that.
MachineInstr *DefMov = nullptr;
if (!SlowPUSHrmm && (DefMov = canFoldIntoRegPush(FrameSetup, Reg))) {
- MachineInstr *Push = BuildMI(MBB, Call, DL, TII->get(X86::PUSH32rmm));
+ MachineInstr *Push =
+ BuildMI(MBB, Context.Call, DL, TII->get(X86::PUSH32rmm));
unsigned NumOps = DefMov->getDesc().getNumOperands();
for (unsigned i = NumOps - X86::AddrNumOperands; i != NumOps; ++i)
DefMov->eraseFromParent();
} else {
- BuildMI(MBB, Call, DL, TII->get(X86::PUSH32r)).addReg(Reg).getInstr();
+ BuildMI(MBB, Context.Call, DL, TII->get(X86::PUSH32r))
+ .addReg(Reg)
+ .getInstr();
}
}
// 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();
+ if (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.
// 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.
+ // to be smarter about folding into pushes.
for (auto I = DefMI; I != FrameSetup; ++I)
if (I->getOpcode() != X86::MOV32rm)
return nullptr;
projects / oota-llvm.git / commitdiff