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authorDimitry Andric <dim@FreeBSD.org>2019-12-20 19:53:05 +0000
committerDimitry Andric <dim@FreeBSD.org>2019-12-20 19:53:05 +0000
commit0b57cec536236d46e3dba9bd041533462f33dbb7 (patch)
tree56229dbdbbf76d18580f72f789003db17246c8d9 /contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
parent718ef55ec7785aae63f98f8ca05dc07ed399c16d (diff)
Notes
Diffstat (limited to 'contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp')
-rw-r--r--contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp445
1 files changed, 0 insertions, 445 deletions
diff --git a/contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp b/contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
deleted file mode 100644
index 69ceacd0c18c..000000000000
--- a/contrib/llvm/lib/CodeGen/LocalStackSlotAllocation.cpp
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@@ -1,445 +0,0 @@
-//===- LocalStackSlotAllocation.cpp - Pre-allocate locals to stack slots --===//
-//
-// 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 pass assigns local frame indices to stack slots relative to one another
-// and allocates additional base registers to access them when the target
-// estimates they are likely to be out of range of stack pointer and frame
-// pointer relative addressing.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallSet.h"
-#include "llvm/ADT/SmallVector.h"
-#include "llvm/ADT/Statistic.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/MachineOperand.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/TargetFrameLowering.h"
-#include "llvm/CodeGen/TargetOpcodes.h"
-#include "llvm/CodeGen/TargetRegisterInfo.h"
-#include "llvm/CodeGen/TargetSubtargetInfo.h"
-#include "llvm/Pass.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/ErrorHandling.h"
-#include "llvm/Support/raw_ostream.h"
-#include <algorithm>
-#include <cassert>
-#include <cstdint>
-#include <tuple>
-
-using namespace llvm;
-
-#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
-
- // Order reference instruction appears in program. Used to ensure
- // deterministic order when multiple instructions may reference the same
- // location.
- unsigned Order;
-
- public:
- FrameRef(MachineInstr *I, int64_t Offset, int Idx, unsigned Ord) :
- MI(I), LocalOffset(Offset), FrameIdx(Idx), Order(Ord) {}
-
- bool operator<(const FrameRef &RHS) const {
- return std::tie(LocalOffset, FrameIdx, Order) <
- std::tie(RHS.LocalOffset, RHS.FrameIdx, RHS.Order);
- }
-
- 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
- using StackObjSet = SmallSetVector<int, 8>;
-
- 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) {
- initializeLocalStackSlotPassPass(*PassRegistry::getPassRegistry());
- }
-
- bool runOnMachineFunction(MachineFunction &MF) override;
-
- void getAnalysisUsage(AnalysisUsage &AU) const override {
- AU.setPreservesCFG();
- MachineFunctionPass::getAnalysisUsage(AU);
- }
- };
-
-} // end anonymous namespace
-
-char LocalStackSlotPass::ID = 0;
-
-char &llvm::LocalStackSlotAllocationID = LocalStackSlotPass::ID;
-INITIALIZE_PASS(LocalStackSlotPass, DEBUG_TYPE,
- "Local Stack Slot Allocation", false, false)
-
-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.
-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
- // increase the stack alignment to match.
- MaxAlign = std::max(MaxAlign, Align);
-
- // Adjust to alignment boundary.
- Offset = (Offset + Align - 1) / Align * Align;
-
- int64_t LocalOffset = StackGrowsDown ? -Offset : Offset;
- LLVM_DEBUG(dbgs() << "Allocate FI(" << FrameIdx << ") to local offset "
- << 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) {
- // 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;
-
- // Make sure that the stack protector comes before the local variables on the
- // stack.
- SmallSet<int, 16> ProtectedObjs;
- if (MFI.hasStackProtectorIndex()) {
- int StackProtectorFI = MFI.getStackProtectorIndex();
-
- // We need to make sure we didn't pre-allocate the stack protector when
- // doing this.
- // If we already have a stack protector, this will re-assign it to a slot
- // that is **not** covering the protected objects.
- assert(!MFI.isObjectPreAllocated(StackProtectorFI) &&
- "Stack protector pre-allocated in LocalStackSlotAllocation");
-
- StackObjSet LargeArrayObjs;
- StackObjSet SmallArrayObjs;
- StackObjSet AddrOfObjs;
-
- AdjustStackOffset(MFI, StackProtectorFI, Offset, StackGrowsDown, MaxAlign);
-
- // Assign large stack objects first.
- for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
- if (MFI.isDeadObjectIndex(i))
- continue;
- if (StackProtectorFI == (int)i)
- continue;
-
- switch (MFI.getObjectSSPLayout(i)) {
- case MachineFrameInfo::SSPLK_None:
- continue;
- case MachineFrameInfo::SSPLK_SmallArray:
- SmallArrayObjs.insert(i);
- continue;
- case MachineFrameInfo::SSPLK_AddrOf:
- AddrOfObjs.insert(i);
- continue;
- case MachineFrameInfo::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
- // callee saved registers.
- for (unsigned i = 0, e = MFI.getObjectIndexEnd(); i != e; ++i) {
- if (MFI.isDeadObjectIndex(i))
- continue;
- if (MFI.getStackProtectorIndex() == (int)i)
- continue;
- if (ProtectedObjs.count(i))
- continue;
-
- 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;
-
- unsigned Order = 0;
-
- for (MachineBasicBlock &BB : Fn) {
- for (MachineInstr &MI : BB) {
- // Debug value, stackmap and patchpoint instructions can't be out of
- // range, so they don't need any updates.
- if (MI.isDebugInstr() || 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, Order++));
- break;
- }
- }
- }
- }
-
- // Sort the frame references by local offset.
- // Use frame index as a tie-breaker in case MI's have the same offset.
- llvm::sort(FrameReferenceInsns);
-
- MachineBasicBlock *Entry = &Fn.front();
-
- 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];
- MachineInstr &MI = *FR.getMachineInstr();
- int64_t LocalOffset = FR.getLocalOffset();
- int FrameIdx = FR.getFrameIndex();
- assert(MFI.isObjectPreAllocated(FrameIdx) &&
- "Only pre-allocated locals expected!");
-
- // We need to keep the references to the stack protector slot through frame
- // index operands so that it gets resolved by PEI rather than this pass.
- // This avoids accesses to the stack protector though virtual base
- // registers, and forces PEI to address it using fp/sp/bp.
- if (MFI.hasStackProtectorIndex() &&
- FrameIdx == MFI.getStackProtectorIndex())
- continue;
-
- LLVM_DEBUG(dbgs() << "Considering: " << MI);
-
- unsigned idx = 0;
- for (unsigned f = MI.getNumOperands(); idx != f; ++idx) {
- if (!MI.getOperand(idx).isFI())
- continue;
-
- if (FrameIdx == MI.getOperand(idx).getIndex())
- break;
- }
-
- assert(idx < MI.getNumOperands() && "Cannot find FI operand");
-
- int64_t Offset = 0;
- int64_t FrameSizeAdjust = StackGrowsDown ? MFI.getLocalFrameSize() : 0;
-
- LLVM_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)) {
- LLVM_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.getMF();
- const TargetRegisterClass *RC = TRI->getPointerRegClass(*MF);
- BaseReg = Fn.getRegInfo().createVirtualRegister(RC);
-
- LLVM_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(MI, BaseReg, Offset);
- LLVM_DEBUG(dbgs() << "Resolved: " << MI);
-
- ++NumReplacements;
- }
-
- return UsedBaseReg;
-}