//
// This pass assigns local frame indices to stack slots relative to one another
// and allocates additional base registers to access them when the target
-// estimates the are likely to be out of range of stack pointer and frame
+// estimates they are likely to be out of range of stack pointer and frame
// pointer relative addressing.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "localstackalloc"
-#include "llvm/Constants.h"
-#include "llvm/DerivedTypes.h"
-#include "llvm/Instructions.h"
-#include "llvm/Intrinsics.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
-#include "llvm/Pass.h"
+#include "llvm/CodeGen/Passes.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/ADT/SmallSet.h"
+#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/CodeGen/StackProtector.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetRegisterInfo.h"
-#include "llvm/Target/TargetFrameInfo.h"
+#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
-STATISTIC(NumAllocations, "Number of frame indices processed");
+#define DEBUG_TYPE "localstackalloc"
+
+STATISTIC(NumAllocations, "Number of frame indices allocated into local block");
+STATISTIC(NumBaseRegisters, "Number of virtual frame base registers allocated");
+STATISTIC(NumReplacements, "Number of frame indices references replaced");
namespace {
+ class FrameRef {
+ MachineBasicBlock::iterator MI; // Instr referencing the frame
+ int64_t LocalOffset; // Local offset of the frame idx referenced
+ int FrameIdx; // The frame index
+ public:
+ FrameRef(MachineBasicBlock::iterator I, int64_t Offset, int Idx) :
+ MI(I), LocalOffset(Offset), FrameIdx(Idx) {}
+ bool operator<(const FrameRef &RHS) const {
+ return LocalOffset < RHS.LocalOffset;
+ }
+ MachineBasicBlock::iterator getMachineInstr() const { return MI; }
+ int64_t getLocalOffset() const { return LocalOffset; }
+ int getFrameIndex() const { return FrameIdx; }
+ };
+
class LocalStackSlotPass: public MachineFunctionPass {
+ SmallVector<int64_t,16> LocalOffsets;
+ /// StackObjSet - A set of stack object indexes
+ typedef SmallSetVector<int, 8> StackObjSet;
+
+ void AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
+ bool StackGrowsDown, unsigned &MaxAlign);
+ void AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
+ SmallSet<int, 16> &ProtectedObjs,
+ MachineFrameInfo *MFI, bool StackGrowsDown,
+ int64_t &Offset, unsigned &MaxAlign);
void calculateFrameObjectOffsets(MachineFunction &Fn);
+ bool insertFrameReferenceRegisters(MachineFunction &Fn);
public:
static char ID; // Pass identification, replacement for typeid
- explicit LocalStackSlotPass() : MachineFunctionPass(ID) { }
- bool runOnMachineFunction(MachineFunction &MF);
+ explicit LocalStackSlotPass() : MachineFunctionPass(ID) {
+ initializeLocalStackSlotPassPass(*PassRegistry::getPassRegistry());
+ }
+ bool runOnMachineFunction(MachineFunction &MF) override;
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+ void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
+ AU.addRequired<StackProtector>();
MachineFunctionPass::getAnalysisUsage(AU);
}
- const char *getPassName() const {
- return "Local Stack Slot Allocation";
- }
private:
};
} // end anonymous namespace
char LocalStackSlotPass::ID = 0;
+char &llvm::LocalStackSlotAllocationID = LocalStackSlotPass::ID;
+INITIALIZE_PASS_BEGIN(LocalStackSlotPass, "localstackalloc",
+ "Local Stack Slot Allocation", false, false)
+INITIALIZE_PASS_DEPENDENCY(StackProtector)
+INITIALIZE_PASS_END(LocalStackSlotPass, "localstackalloc",
+ "Local Stack Slot Allocation", false, false)
-FunctionPass *llvm::createLocalStackSlotAllocationPass() {
- return new LocalStackSlotPass();
-}
bool LocalStackSlotPass::runOnMachineFunction(MachineFunction &MF) {
+ MachineFrameInfo *MFI = MF.getFrameInfo();
+ const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
+ unsigned LocalObjectCount = MFI->getObjectIndexEnd();
+
+ // If the target doesn't want/need this pass, or if there are no locals
+ // to consider, early exit.
+ if (!TRI->requiresVirtualBaseRegisters(MF) || LocalObjectCount == 0)
+ return true;
+
+ // Make sure we have enough space to store the local offsets.
+ LocalOffsets.resize(MFI->getObjectIndexEnd());
+
+ // Lay out the local blob.
calculateFrameObjectOffsets(MF);
+
+ // Insert virtual base registers to resolve frame index references.
+ bool UsedBaseRegs = insertFrameReferenceRegisters(MF);
+
+ // Tell MFI whether any base registers were allocated. PEI will only
+ // want to use the local block allocations from this pass if there were any.
+ // Otherwise, PEI can do a bit better job of getting the alignment right
+ // without a hole at the start since it knows the alignment of the stack
+ // at the start of local allocation, and this pass doesn't.
+ MFI->setUseLocalStackAllocationBlock(UsedBaseRegs);
+
return true;
}
/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
-static inline void
-AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx, int64_t &Offset,
- unsigned &MaxAlign) {
+void LocalStackSlotPass::AdjustStackOffset(MachineFrameInfo *MFI,
+ int FrameIdx, int64_t &Offset,
+ bool StackGrowsDown,
+ unsigned &MaxAlign) {
+ // If the stack grows down, add the object size to find the lowest address.
+ if (StackGrowsDown)
+ Offset += MFI->getObjectSize(FrameIdx);
+
unsigned Align = MFI->getObjectAlignment(FrameIdx);
// If the alignment of this object is greater than that of the stack, then
// Adjust to alignment boundary.
Offset = (Offset + Align - 1) / Align * Align;
+ int64_t LocalOffset = StackGrowsDown ? -Offset : Offset;
DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
- << Offset << "\n");
- MFI->mapLocalFrameObject(FrameIdx, Offset);
- Offset += MFI->getObjectSize(FrameIdx);
+ << LocalOffset << "\n");
+ // Keep the offset available for base register allocation
+ LocalOffsets[FrameIdx] = LocalOffset;
+ // And tell MFI about it for PEI to use later
+ MFI->mapLocalFrameObject(FrameIdx, LocalOffset);
+
+ if (!StackGrowsDown)
+ Offset += MFI->getObjectSize(FrameIdx);
++NumAllocations;
}
+/// AssignProtectedObjSet - Helper function to assign large stack objects (i.e.,
+/// those required to be close to the Stack Protector) to stack offsets.
+void LocalStackSlotPass::AssignProtectedObjSet(const StackObjSet &UnassignedObjs,
+ SmallSet<int, 16> &ProtectedObjs,
+ MachineFrameInfo *MFI,
+ bool StackGrowsDown, int64_t &Offset,
+ unsigned &MaxAlign) {
+
+ for (StackObjSet::const_iterator I = UnassignedObjs.begin(),
+ E = UnassignedObjs.end(); I != E; ++I) {
+ int i = *I;
+ AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
+ ProtectedObjs.insert(i);
+ }
+}
+
/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
/// abstract stack objects.
///
void LocalStackSlotPass::calculateFrameObjectOffsets(MachineFunction &Fn) {
- const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
-
// Loop over all of the stack objects, assigning sequential addresses...
MachineFrameInfo *MFI = Fn.getFrameInfo();
+ const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
+ bool StackGrowsDown =
+ TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
int64_t Offset = 0;
unsigned MaxAlign = 0;
+ StackProtector *SP = &getAnalysis<StackProtector>();
// Make sure that the stack protector comes before the local variables on the
// stack.
- SmallSet<int, 16> LargeStackObjs;
+ SmallSet<int, 16> ProtectedObjs;
if (MFI->getStackProtectorIndex() >= 0) {
- AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset, MaxAlign);
+ StackObjSet LargeArrayObjs;
+ StackObjSet SmallArrayObjs;
+ StackObjSet AddrOfObjs;
+
+ AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), Offset,
+ StackGrowsDown, MaxAlign);
// Assign large stack objects first.
for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
- if (!MFI->MayNeedStackProtector(i))
- continue;
- AdjustStackOffset(MFI, i, Offset, MaxAlign);
- LargeStackObjs.insert(i);
+ switch (SP->getSSPLayout(MFI->getObjectAllocation(i))) {
+ case StackProtector::SSPLK_None:
+ continue;
+ case StackProtector::SSPLK_SmallArray:
+ SmallArrayObjs.insert(i);
+ continue;
+ case StackProtector::SSPLK_AddrOf:
+ AddrOfObjs.insert(i);
+ continue;
+ case StackProtector::SSPLK_LargeArray:
+ LargeArrayObjs.insert(i);
+ continue;
+ }
+ llvm_unreachable("Unexpected SSPLayoutKind.");
}
+
+ AssignProtectedObjSet(LargeArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
+ Offset, MaxAlign);
+ AssignProtectedObjSet(SmallArrayObjs, ProtectedObjs, MFI, StackGrowsDown,
+ Offset, MaxAlign);
+ AssignProtectedObjSet(AddrOfObjs, ProtectedObjs, MFI, StackGrowsDown,
+ Offset, MaxAlign);
}
// Then assign frame offsets to stack objects that are not used to spill
continue;
if (MFI->getStackProtectorIndex() == (int)i)
continue;
- if (LargeStackObjs.count(i))
+ if (ProtectedObjs.count(i))
continue;
- AdjustStackOffset(MFI, i, Offset, MaxAlign);
+ AdjustStackOffset(MFI, i, Offset, StackGrowsDown, MaxAlign);
}
// Remember how big this blob of stack space is
MFI->setLocalFrameSize(Offset);
MFI->setLocalFrameMaxAlign(MaxAlign);
}
+
+static inline bool
+lookupCandidateBaseReg(unsigned BaseReg,
+ int64_t BaseOffset,
+ int64_t FrameSizeAdjust,
+ int64_t LocalFrameOffset,
+ const MachineInstr *MI,
+ const TargetRegisterInfo *TRI) {
+ // Check if the relative offset from the where the base register references
+ // to the target address is in range for the instruction.
+ int64_t Offset = FrameSizeAdjust + LocalFrameOffset - BaseOffset;
+ return TRI->isFrameOffsetLegal(MI, BaseReg, Offset);
+}
+
+bool LocalStackSlotPass::insertFrameReferenceRegisters(MachineFunction &Fn) {
+ // Scan the function's instructions looking for frame index references.
+ // For each, ask the target if it wants a virtual base register for it
+ // based on what we can tell it about where the local will end up in the
+ // stack frame. If it wants one, re-use a suitable one we've previously
+ // allocated, or if there isn't one that fits the bill, allocate a new one
+ // and ask the target to create a defining instruction for it.
+ bool UsedBaseReg = false;
+
+ MachineFrameInfo *MFI = Fn.getFrameInfo();
+ const TargetRegisterInfo *TRI = Fn.getSubtarget().getRegisterInfo();
+ const TargetFrameLowering &TFI = *Fn.getSubtarget().getFrameLowering();
+ bool StackGrowsDown =
+ TFI.getStackGrowthDirection() == TargetFrameLowering::StackGrowsDown;
+
+ // Collect all of the instructions in the block that reference
+ // a frame index. Also store the frame index referenced to ease later
+ // lookup. (For any insn that has more than one FI reference, we arbitrarily
+ // choose the first one).
+ SmallVector<FrameRef, 64> FrameReferenceInsns;
+
+ for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB) {
+ for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I) {
+ MachineInstr *MI = I;
+
+ // Debug value, stackmap and patchpoint instructions can't be out of
+ // range, so they don't need any updates.
+ if (MI->isDebugValue() ||
+ MI->getOpcode() == TargetOpcode::STATEPOINT ||
+ MI->getOpcode() == TargetOpcode::STACKMAP ||
+ MI->getOpcode() == TargetOpcode::PATCHPOINT)
+ continue;
+
+ // For now, allocate the base register(s) within the basic block
+ // where they're used, and don't try to keep them around outside
+ // of that. It may be beneficial to try sharing them more broadly
+ // than that, but the increased register pressure makes that a
+ // tricky thing to balance. Investigate if re-materializing these
+ // becomes an issue.
+ for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
+ // Consider replacing all frame index operands that reference
+ // an object allocated in the local block.
+ if (MI->getOperand(i).isFI()) {
+ // Don't try this with values not in the local block.
+ if (!MFI->isObjectPreAllocated(MI->getOperand(i).getIndex()))
+ break;
+ int Idx = MI->getOperand(i).getIndex();
+ int64_t LocalOffset = LocalOffsets[Idx];
+ if (!TRI->needsFrameBaseReg(MI, LocalOffset))
+ break;
+ FrameReferenceInsns.
+ push_back(FrameRef(MI, LocalOffset, Idx));
+ break;
+ }
+ }
+ }
+ }
+
+ // Sort the frame references by local offset
+ array_pod_sort(FrameReferenceInsns.begin(), FrameReferenceInsns.end());
+
+ MachineBasicBlock *Entry = Fn.begin();
+
+ unsigned BaseReg = 0;
+ int64_t BaseOffset = 0;
+
+ // Loop through the frame references and allocate for them as necessary.
+ for (int ref = 0, e = FrameReferenceInsns.size(); ref < e ; ++ref) {
+ FrameRef &FR = FrameReferenceInsns[ref];
+ MachineBasicBlock::iterator I = FR.getMachineInstr();
+ MachineInstr *MI = I;
+ int64_t LocalOffset = FR.getLocalOffset();
+ int FrameIdx = FR.getFrameIndex();
+ assert(MFI->isObjectPreAllocated(FrameIdx) &&
+ "Only pre-allocated locals expected!");
+
+ DEBUG(dbgs() << "Considering: " << *MI);
+
+ unsigned idx = 0;
+ for (unsigned f = MI->getNumOperands(); idx != f; ++idx) {
+ if (!MI->getOperand(idx).isFI())
+ continue;
+
+ if (FrameIdx == I->getOperand(idx).getIndex())
+ break;
+ }
+
+ assert(idx < MI->getNumOperands() && "Cannot find FI operand");
+
+ int64_t Offset = 0;
+ int64_t FrameSizeAdjust = StackGrowsDown ? MFI->getLocalFrameSize() : 0;
+
+ DEBUG(dbgs() << " Replacing FI in: " << *MI);
+
+ // If we have a suitable base register available, use it; otherwise
+ // create a new one. Note that any offset encoded in the
+ // instruction itself will be taken into account by the target,
+ // so we don't have to adjust for it here when reusing a base
+ // register.
+ if (UsedBaseReg && lookupCandidateBaseReg(BaseReg, BaseOffset,
+ FrameSizeAdjust, LocalOffset, MI,
+ TRI)) {
+ DEBUG(dbgs() << " Reusing base register " << BaseReg << "\n");
+ // We found a register to reuse.
+ Offset = FrameSizeAdjust + LocalOffset - BaseOffset;
+ } else {
+ // No previously defined register was in range, so create a // new one.
+
+ int64_t InstrOffset = TRI->getFrameIndexInstrOffset(MI, idx);
+
+ int64_t PrevBaseOffset = BaseOffset;
+ BaseOffset = FrameSizeAdjust + LocalOffset + InstrOffset;
+
+ // We'd like to avoid creating single-use virtual base registers.
+ // Because the FrameRefs are in sorted order, and we've already
+ // processed all FrameRefs before this one, just check whether or not
+ // the next FrameRef will be able to reuse this new register. If not,
+ // then don't bother creating it.
+ if (ref + 1 >= e ||
+ !lookupCandidateBaseReg(
+ BaseReg, BaseOffset, FrameSizeAdjust,
+ FrameReferenceInsns[ref + 1].getLocalOffset(),
+ FrameReferenceInsns[ref + 1].getMachineInstr(), TRI)) {
+ BaseOffset = PrevBaseOffset;
+ continue;
+ }
+
+ const MachineFunction *MF = MI->getParent()->getParent();
+ const TargetRegisterClass *RC = TRI->getPointerRegClass(*MF);
+ BaseReg = Fn.getRegInfo().createVirtualRegister(RC);
+
+ DEBUG(dbgs() << " Materializing base register " << BaseReg <<
+ " at frame local offset " << LocalOffset + InstrOffset << "\n");
+
+ // Tell the target to insert the instruction to initialize
+ // the base register.
+ // MachineBasicBlock::iterator InsertionPt = Entry->begin();
+ TRI->materializeFrameBaseRegister(Entry, BaseReg, FrameIdx,
+ InstrOffset);
+
+ // The base register already includes any offset specified
+ // by the instruction, so account for that so it doesn't get
+ // applied twice.
+ Offset = -InstrOffset;
+
+ ++NumBaseRegisters;
+ UsedBaseReg = true;
+ }
+ assert(BaseReg != 0 && "Unable to allocate virtual base register!");
+
+ // Modify the instruction to use the new base register rather
+ // than the frame index operand.
+ TRI->resolveFrameIndex(*I, BaseReg, Offset);
+ DEBUG(dbgs() << "Resolved: " << *MI);
+
+ ++NumReplacements;
+ }
+
+ return UsedBaseReg;
+}
projects / oota-llvm.git / blobdiff