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//===-- PrologEpilogInserter.cpp - Insert Prolog/Epilog code in function --===//
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// The LLVM Compiler Infrastructure
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//===----------------------------------------------------------------------===//
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// This pass is responsible for finalizing the functions frame layout, saving
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// callee saved registers, and for emitting prolog & epilog code for the
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// This pass must be run after register allocation. After this pass is
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// executed, it is illegal to construct MO_FrameIndex operands.
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// This pass provides an optional shrink wrapping variant of prolog/epilog
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// insertion, enabled via --shrink-wrap. See ShrinkWrapping.cpp.
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "pei"
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#include "PrologEpilogInserter.h"
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#include "llvm/CodeGen/MachineDominators.h"
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#include "llvm/CodeGen/MachineLoopInfo.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineFrameInfo.h"
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#include "llvm/CodeGen/MachineRegisterInfo.h"
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#include "llvm/CodeGen/RegisterScavenging.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetRegisterInfo.h"
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#include "llvm/Target/TargetFrameInfo.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Support/CommandLine.h"
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/ADT/IndexedMap.h"
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#include "llvm/ADT/SmallSet.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/ADT/STLExtras.h"
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INITIALIZE_PASS(PEI, "prologepilog",
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"Prologue/Epilogue Insertion", false, false);
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STATISTIC(NumVirtualFrameRegs, "Number of virtual frame regs encountered");
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STATISTIC(NumScavengedRegs, "Number of frame index regs scavenged");
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/// createPrologEpilogCodeInserter - This function returns a pass that inserts
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/// prolog and epilog code, and eliminates abstract frame references.
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FunctionPass *llvm::createPrologEpilogCodeInserter() { return new PEI(); }
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/// runOnMachineFunction - Insert prolog/epilog code and replace abstract
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/// frame indexes with appropriate references.
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bool PEI::runOnMachineFunction(MachineFunction &Fn) {
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const Function* F = Fn.getFunction();
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const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
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RS = TRI->requiresRegisterScavenging(Fn) ? new RegScavenger() : NULL;
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FrameIndexVirtualScavenging = TRI->requiresFrameIndexScavenging(Fn);
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// Calculate the MaxCallFrameSize and AdjustsStack variables for the
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// function's frame information. Also eliminates call frame pseudo
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calculateCallsInformation(Fn);
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// Allow the target machine to make some adjustments to the function
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// e.g. UsedPhysRegs before calculateCalleeSavedRegisters.
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TRI->processFunctionBeforeCalleeSavedScan(Fn, RS);
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// Scan the function for modified callee saved registers and insert spill code
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// for any callee saved registers that are modified.
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calculateCalleeSavedRegisters(Fn);
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// Determine placement of CSR spill/restore code:
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// - With shrink wrapping, place spills and restores to tightly
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// enclose regions in the Machine CFG of the function where
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// - Without shink wrapping (default), place all spills in the
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// entry block, all restores in return blocks.
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placeCSRSpillsAndRestores(Fn);
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// Add the code to save and restore the callee saved registers
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if (!F->hasFnAttr(Attribute::Naked))
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insertCSRSpillsAndRestores(Fn);
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// Allow the target machine to make final modifications to the function
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// before the frame layout is finalized.
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TRI->processFunctionBeforeFrameFinalized(Fn);
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// Calculate actual frame offsets for all abstract stack objects...
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calculateFrameObjectOffsets(Fn);
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// Add prolog and epilog code to the function. This function is required
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// to align the stack frame as necessary for any stack variables or
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// called functions. Because of this, calculateCalleeSavedRegisters()
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// must be called before this function in order to set the AdjustsStack
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// and MaxCallFrameSize variables.
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if (!F->hasFnAttr(Attribute::Naked))
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insertPrologEpilogCode(Fn);
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// Replace all MO_FrameIndex operands with physical register references
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// and actual offsets.
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replaceFrameIndices(Fn);
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// If register scavenging is needed, as we've enabled doing it as a
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// post-pass, scavenge the virtual registers that frame index elimiation
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if (TRI->requiresRegisterScavenging(Fn) && FrameIndexVirtualScavenging)
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scavengeFrameVirtualRegs(Fn);
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void PEI::getAnalysisUsage(AnalysisUsage &AU) const {
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AU.setPreservesCFG();
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if (ShrinkWrapping || ShrinkWrapFunc != "") {
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AU.addRequired<MachineLoopInfo>();
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AU.addRequired<MachineDominatorTree>();
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AU.addPreserved<MachineLoopInfo>();
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AU.addPreserved<MachineDominatorTree>();
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MachineFunctionPass::getAnalysisUsage(AU);
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/// calculateCallsInformation - Calculate the MaxCallFrameSize and AdjustsStack
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/// variables for the function's frame information and eliminate call frame
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/// pseudo instructions.
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void PEI::calculateCallsInformation(MachineFunction &Fn) {
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const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
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MachineFrameInfo *MFI = Fn.getFrameInfo();
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unsigned MaxCallFrameSize = 0;
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bool AdjustsStack = MFI->adjustsStack();
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// Get the function call frame set-up and tear-down instruction opcode
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int FrameSetupOpcode = RegInfo->getCallFrameSetupOpcode();
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int FrameDestroyOpcode = RegInfo->getCallFrameDestroyOpcode();
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// Early exit for targets which have no call frame setup/destroy pseudo
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if (FrameSetupOpcode == -1 && FrameDestroyOpcode == -1)
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std::vector<MachineBasicBlock::iterator> FrameSDOps;
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for (MachineFunction::iterator BB = Fn.begin(), E = Fn.end(); BB != E; ++BB)
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for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ++I)
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if (I->getOpcode() == FrameSetupOpcode ||
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I->getOpcode() == FrameDestroyOpcode) {
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assert(I->getNumOperands() >= 1 && "Call Frame Setup/Destroy Pseudo"
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" instructions should have a single immediate argument!");
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unsigned Size = I->getOperand(0).getImm();
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if (Size > MaxCallFrameSize) MaxCallFrameSize = Size;
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FrameSDOps.push_back(I);
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} else if (I->isInlineAsm()) {
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// Some inline asm's need a stack frame, as indicated by operand 1.
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if (I->getOperand(1).getImm())
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MFI->setAdjustsStack(AdjustsStack);
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MFI->setMaxCallFrameSize(MaxCallFrameSize);
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for (std::vector<MachineBasicBlock::iterator>::iterator
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i = FrameSDOps.begin(), e = FrameSDOps.end(); i != e; ++i) {
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MachineBasicBlock::iterator I = *i;
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// If call frames are not being included as part of the stack frame, and
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// the target doesn't indicate otherwise, remove the call frame pseudos
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// here. The sub/add sp instruction pairs are still inserted, but we don't
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// need to track the SP adjustment for frame index elimination.
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if (RegInfo->canSimplifyCallFramePseudos(Fn))
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RegInfo->eliminateCallFramePseudoInstr(Fn, *I->getParent(), I);
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/// calculateCalleeSavedRegisters - Scan the function for modified callee saved
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void PEI::calculateCalleeSavedRegisters(MachineFunction &Fn) {
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const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
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const TargetFrameInfo *TFI = Fn.getTarget().getFrameInfo();
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MachineFrameInfo *MFI = Fn.getFrameInfo();
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// Get the callee saved register list...
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const unsigned *CSRegs = RegInfo->getCalleeSavedRegs(&Fn);
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// These are used to keep track the callee-save area. Initialize them.
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MinCSFrameIndex = INT_MAX;
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// Early exit for targets which have no callee saved registers.
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if (CSRegs == 0 || CSRegs[0] == 0)
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// In Naked functions we aren't going to save any registers.
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if (Fn.getFunction()->hasFnAttr(Attribute::Naked))
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std::vector<CalleeSavedInfo> CSI;
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for (unsigned i = 0; CSRegs[i]; ++i) {
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unsigned Reg = CSRegs[i];
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if (Fn.getRegInfo().isPhysRegUsed(Reg)) {
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// If the reg is modified, save it!
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CSI.push_back(CalleeSavedInfo(Reg));
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for (const unsigned *AliasSet = RegInfo->getAliasSet(Reg);
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*AliasSet; ++AliasSet) { // Check alias registers too.
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if (Fn.getRegInfo().isPhysRegUsed(*AliasSet)) {
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CSI.push_back(CalleeSavedInfo(Reg));
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return; // Early exit if no callee saved registers are modified!
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unsigned NumFixedSpillSlots;
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const TargetFrameInfo::SpillSlot *FixedSpillSlots =
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TFI->getCalleeSavedSpillSlots(NumFixedSpillSlots);
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// Now that we know which registers need to be saved and restored, allocate
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// stack slots for them.
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for (std::vector<CalleeSavedInfo>::iterator
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I = CSI.begin(), E = CSI.end(); I != E; ++I) {
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unsigned Reg = I->getReg();
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const TargetRegisterClass *RC = RegInfo->getMinimalPhysRegClass(Reg);
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if (RegInfo->hasReservedSpillSlot(Fn, Reg, FrameIdx)) {
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I->setFrameIdx(FrameIdx);
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// Check to see if this physreg must be spilled to a particular stack slot
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const TargetFrameInfo::SpillSlot *FixedSlot = FixedSpillSlots;
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while (FixedSlot != FixedSpillSlots+NumFixedSpillSlots &&
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FixedSlot->Reg != Reg)
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if (FixedSlot == FixedSpillSlots + NumFixedSpillSlots) {
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// Nope, just spill it anywhere convenient.
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unsigned Align = RC->getAlignment();
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unsigned StackAlign = TFI->getStackAlignment();
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// We may not be able to satisfy the desired alignment specification of
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// the TargetRegisterClass if the stack alignment is smaller. Use the
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Align = std::min(Align, StackAlign);
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FrameIdx = MFI->CreateStackObject(RC->getSize(), Align, true);
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if ((unsigned)FrameIdx < MinCSFrameIndex) MinCSFrameIndex = FrameIdx;
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if ((unsigned)FrameIdx > MaxCSFrameIndex) MaxCSFrameIndex = FrameIdx;
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// Spill it to the stack where we must.
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FrameIdx = MFI->CreateFixedObject(RC->getSize(), FixedSlot->Offset, true);
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I->setFrameIdx(FrameIdx);
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MFI->setCalleeSavedInfo(CSI);
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/// insertCSRSpillsAndRestores - Insert spill and restore code for
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/// callee saved registers used in the function, handling shrink wrapping.
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void PEI::insertCSRSpillsAndRestores(MachineFunction &Fn) {
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// Get callee saved register information.
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MachineFrameInfo *MFI = Fn.getFrameInfo();
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const std::vector<CalleeSavedInfo> &CSI = MFI->getCalleeSavedInfo();
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MFI->setCalleeSavedInfoValid(true);
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// Early exit if no callee saved registers are modified!
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const TargetInstrInfo &TII = *Fn.getTarget().getInstrInfo();
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const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
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MachineBasicBlock::iterator I;
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if (! ShrinkWrapThisFunction) {
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// Spill using target interface.
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I = EntryBlock->begin();
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if (!TII.spillCalleeSavedRegisters(*EntryBlock, I, CSI, TRI)) {
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for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
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// Add the callee-saved register as live-in.
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// It's killed at the spill.
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EntryBlock->addLiveIn(CSI[i].getReg());
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// Insert the spill to the stack frame.
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unsigned Reg = CSI[i].getReg();
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const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
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TII.storeRegToStackSlot(*EntryBlock, I, Reg, true,
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CSI[i].getFrameIdx(), RC, TRI);
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// Restore using target interface.
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for (unsigned ri = 0, re = ReturnBlocks.size(); ri != re; ++ri) {
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MachineBasicBlock* MBB = ReturnBlocks[ri];
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// Skip over all terminator instructions, which are part of the return
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MachineBasicBlock::iterator I2 = I;
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while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
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bool AtStart = I == MBB->begin();
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MachineBasicBlock::iterator BeforeI = I;
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// Restore all registers immediately before the return and any
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// terminators that preceed it.
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if (!TII.restoreCalleeSavedRegisters(*MBB, I, CSI, TRI)) {
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for (unsigned i = 0, e = CSI.size(); i != e; ++i) {
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unsigned Reg = CSI[i].getReg();
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const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
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TII.loadRegFromStackSlot(*MBB, I, Reg,
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CSI[i].getFrameIdx(),
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assert(I != MBB->begin() &&
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"loadRegFromStackSlot didn't insert any code!");
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// Insert in reverse order. loadRegFromStackSlot can insert
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// multiple instructions.
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std::vector<CalleeSavedInfo> blockCSI;
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for (CSRegBlockMap::iterator BI = CSRSave.begin(),
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BE = CSRSave.end(); BI != BE; ++BI) {
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MachineBasicBlock* MBB = BI->first;
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CSRegSet save = BI->second;
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for (CSRegSet::iterator RI = save.begin(),
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RE = save.end(); RI != RE; ++RI) {
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blockCSI.push_back(CSI[*RI]);
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assert(blockCSI.size() > 0 &&
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"Could not collect callee saved register info");
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// When shrink wrapping, use stack slot stores/loads.
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for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
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// Add the callee-saved register as live-in.
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// It's killed at the spill.
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MBB->addLiveIn(blockCSI[i].getReg());
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// Insert the spill to the stack frame.
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unsigned Reg = blockCSI[i].getReg();
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const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
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TII.storeRegToStackSlot(*MBB, I, Reg,
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blockCSI[i].getFrameIdx(),
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for (CSRegBlockMap::iterator BI = CSRRestore.begin(),
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BE = CSRRestore.end(); BI != BE; ++BI) {
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MachineBasicBlock* MBB = BI->first;
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CSRegSet restore = BI->second;
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for (CSRegSet::iterator RI = restore.begin(),
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RE = restore.end(); RI != RE; ++RI) {
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blockCSI.push_back(CSI[*RI]);
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assert(blockCSI.size() > 0 &&
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"Could not find callee saved register info");
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// If MBB is empty and needs restores, insert at the _beginning_.
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// Skip over all terminator instructions, which are part of the
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if (! I->getDesc().isTerminator()) {
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MachineBasicBlock::iterator I2 = I;
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while (I2 != MBB->begin() && (--I2)->getDesc().isTerminator())
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bool AtStart = I == MBB->begin();
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MachineBasicBlock::iterator BeforeI = I;
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// Restore all registers immediately before the return and any
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// terminators that preceed it.
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for (unsigned i = 0, e = blockCSI.size(); i != e; ++i) {
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unsigned Reg = blockCSI[i].getReg();
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const TargetRegisterClass *RC = TRI->getMinimalPhysRegClass(Reg);
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TII.loadRegFromStackSlot(*MBB, I, Reg,
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blockCSI[i].getFrameIdx(),
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assert(I != MBB->begin() &&
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"loadRegFromStackSlot didn't insert any code!");
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// Insert in reverse order. loadRegFromStackSlot can insert
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// multiple instructions.
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/// AdjustStackOffset - Helper function used to adjust the stack frame offset.
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AdjustStackOffset(MachineFrameInfo *MFI, int FrameIdx,
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bool StackGrowsDown, int64_t &Offset,
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unsigned &MaxAlign) {
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// If the stack grows down, add the object size to find the lowest address.
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Offset += MFI->getObjectSize(FrameIdx);
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unsigned Align = MFI->getObjectAlignment(FrameIdx);
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// If the alignment of this object is greater than that of the stack, then
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// increase the stack alignment to match.
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MaxAlign = std::max(MaxAlign, Align);
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// Adjust to alignment boundary.
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Offset = (Offset + Align - 1) / Align * Align;
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if (StackGrowsDown) {
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DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << -Offset << "]\n");
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MFI->setObjectOffset(FrameIdx, -Offset); // Set the computed offset
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DEBUG(dbgs() << "alloc FI(" << FrameIdx << ") at SP[" << Offset << "]\n");
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MFI->setObjectOffset(FrameIdx, Offset);
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Offset += MFI->getObjectSize(FrameIdx);
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/// calculateFrameObjectOffsets - Calculate actual frame offsets for all of the
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/// abstract stack objects.
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void PEI::calculateFrameObjectOffsets(MachineFunction &Fn) {
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const TargetFrameInfo &TFI = *Fn.getTarget().getFrameInfo();
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bool StackGrowsDown =
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TFI.getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
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// Loop over all of the stack objects, assigning sequential addresses...
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MachineFrameInfo *MFI = Fn.getFrameInfo();
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// Start at the beginning of the local area.
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// The Offset is the distance from the stack top in the direction
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// of stack growth -- so it's always nonnegative.
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int LocalAreaOffset = TFI.getOffsetOfLocalArea();
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LocalAreaOffset = -LocalAreaOffset;
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assert(LocalAreaOffset >= 0
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&& "Local area offset should be in direction of stack growth");
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int64_t Offset = LocalAreaOffset;
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// If there are fixed sized objects that are preallocated in the local area,
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// non-fixed objects can't be allocated right at the start of local area.
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// We currently don't support filling in holes in between fixed sized
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// objects, so we adjust 'Offset' to point to the end of last fixed sized
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// preallocated object.
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for (int i = MFI->getObjectIndexBegin(); i != 0; ++i) {
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if (StackGrowsDown) {
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// The maximum distance from the stack pointer is at lower address of
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// the object -- which is given by offset. For down growing stack
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// the offset is negative, so we negate the offset to get the distance.
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FixedOff = -MFI->getObjectOffset(i);
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// The maximum distance from the start pointer is at the upper
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// address of the object.
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FixedOff = MFI->getObjectOffset(i) + MFI->getObjectSize(i);
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if (FixedOff > Offset) Offset = FixedOff;
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// First assign frame offsets to stack objects that are used to spill
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// callee saved registers.
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if (StackGrowsDown) {
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for (unsigned i = MinCSFrameIndex; i <= MaxCSFrameIndex; ++i) {
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// If the stack grows down, we need to add the size to find the lowest
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// address of the object.
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Offset += MFI->getObjectSize(i);
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unsigned Align = MFI->getObjectAlignment(i);
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// Adjust to alignment boundary
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Offset = (Offset+Align-1)/Align*Align;
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MFI->setObjectOffset(i, -Offset); // Set the computed offset
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int MaxCSFI = MaxCSFrameIndex, MinCSFI = MinCSFrameIndex;
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for (int i = MaxCSFI; i >= MinCSFI ; --i) {
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unsigned Align = MFI->getObjectAlignment(i);
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// Adjust to alignment boundary
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Offset = (Offset+Align-1)/Align*Align;
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MFI->setObjectOffset(i, Offset);
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Offset += MFI->getObjectSize(i);
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unsigned MaxAlign = MFI->getMaxAlignment();
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// Make sure the special register scavenging spill slot is closest to the
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// frame pointer if a frame pointer is required.
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const TargetRegisterInfo *RegInfo = Fn.getTarget().getRegisterInfo();
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if (RS && RegInfo->hasFP(Fn) && !RegInfo->needsStackRealignment(Fn)) {
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int SFI = RS->getScavengingFrameIndex();
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AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
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// FIXME: Once this is working, then enable flag will change to a target
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// check for whether the frame is large enough to want to use virtual
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// frame index registers. Functions which don't want/need this optimization
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// will continue to use the existing code path.
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if (MFI->getUseLocalStackAllocationBlock()) {
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unsigned Align = MFI->getLocalFrameMaxAlign();
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// Adjust to alignment boundary.
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Offset = (Offset + Align - 1) / Align * Align;
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DEBUG(dbgs() << "Local frame base offset: " << Offset << "\n");
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// Resolve offsets for objects in the local block.
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for (unsigned i = 0, e = MFI->getLocalFrameObjectCount(); i != e; ++i) {
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std::pair<int, int64_t> Entry = MFI->getLocalFrameObjectMap(i);
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int64_t FIOffset = (StackGrowsDown ? -Offset : Offset) + Entry.second;
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DEBUG(dbgs() << "alloc FI(" << Entry.first << ") at SP[" <<
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MFI->setObjectOffset(Entry.first, FIOffset);
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// Allocate the local block
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Offset += MFI->getLocalFrameSize();
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MaxAlign = std::max(Align, MaxAlign);
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// Make sure that the stack protector comes before the local variables on the
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SmallSet<int, 16> LargeStackObjs;
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if (MFI->getStackProtectorIndex() >= 0) {
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AdjustStackOffset(MFI, MFI->getStackProtectorIndex(), StackGrowsDown,
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// Assign large stack objects first.
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for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
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if (MFI->isObjectPreAllocated(i) &&
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MFI->getUseLocalStackAllocationBlock())
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if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
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if (RS && (int)i == RS->getScavengingFrameIndex())
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if (MFI->isDeadObjectIndex(i))
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if (MFI->getStackProtectorIndex() == (int)i)
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if (!MFI->MayNeedStackProtector(i))
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AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
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LargeStackObjs.insert(i);
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// Then assign frame offsets to stack objects that are not used to spill
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// callee saved registers.
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for (unsigned i = 0, e = MFI->getObjectIndexEnd(); i != e; ++i) {
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if (MFI->isObjectPreAllocated(i) &&
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MFI->getUseLocalStackAllocationBlock())
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if (i >= MinCSFrameIndex && i <= MaxCSFrameIndex)
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if (RS && (int)i == RS->getScavengingFrameIndex())
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if (MFI->isDeadObjectIndex(i))
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if (MFI->getStackProtectorIndex() == (int)i)
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if (LargeStackObjs.count(i))
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AdjustStackOffset(MFI, i, StackGrowsDown, Offset, MaxAlign);
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// Make sure the special register scavenging spill slot is closest to the
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if (RS && (!RegInfo->hasFP(Fn) || RegInfo->needsStackRealignment(Fn))) {
635
int SFI = RS->getScavengingFrameIndex();
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AdjustStackOffset(MFI, SFI, StackGrowsDown, Offset, MaxAlign);
640
if (!RegInfo->targetHandlesStackFrameRounding()) {
641
// If we have reserved argument space for call sites in the function
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// immediately on entry to the current function, count it as part of the
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// overall stack size.
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if (MFI->adjustsStack() && RegInfo->hasReservedCallFrame(Fn))
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Offset += MFI->getMaxCallFrameSize();
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// Round up the size to a multiple of the alignment. If the function has
648
// any calls or alloca's, align to the target's StackAlignment value to
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// ensure that the callee's frame or the alloca data is suitably aligned;
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// otherwise, for leaf functions, align to the TransientStackAlignment
653
if (MFI->adjustsStack() || MFI->hasVarSizedObjects() ||
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(RegInfo->needsStackRealignment(Fn) && MFI->getObjectIndexEnd() != 0))
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StackAlign = TFI.getStackAlignment();
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StackAlign = TFI.getTransientStackAlignment();
659
// If the frame pointer is eliminated, all frame offsets will be relative to
660
// SP not FP. Align to MaxAlign so this works.
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StackAlign = std::max(StackAlign, MaxAlign);
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unsigned AlignMask = StackAlign - 1;
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Offset = (Offset + AlignMask) & ~uint64_t(AlignMask);
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// Update frame info to pretend that this is part of the stack...
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MFI->setStackSize(Offset - LocalAreaOffset);
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/// insertPrologEpilogCode - Scan the function for modified callee saved
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/// registers, insert spill code for these callee saved registers, then add
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/// prolog and epilog code to the function.
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void PEI::insertPrologEpilogCode(MachineFunction &Fn) {
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const TargetRegisterInfo *TRI = Fn.getTarget().getRegisterInfo();
677
// Add prologue to the function...
678
TRI->emitPrologue(Fn);
680
// Add epilogue to restore the callee-save registers in each exiting block
681
for (MachineFunction::iterator I = Fn.begin(), E = Fn.end(); I != E; ++I) {
682
// If last instruction is a return instruction, add an epilogue
683
if (!I->empty() && I->back().getDesc().isReturn())
684
TRI->emitEpilogue(Fn, *I);
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/// replaceFrameIndices - Replace all MO_FrameIndex operands with physical
689
/// register references and actual offsets.
691
void PEI::replaceFrameIndices(MachineFunction &Fn) {
692
if (!Fn.getFrameInfo()->hasStackObjects()) return; // Nothing to do?
694
const TargetMachine &TM = Fn.getTarget();
695
assert(TM.getRegisterInfo() && "TM::getRegisterInfo() must be implemented!");
696
const TargetRegisterInfo &TRI = *TM.getRegisterInfo();
697
const TargetFrameInfo *TFI = TM.getFrameInfo();
698
bool StackGrowsDown =
699
TFI->getStackGrowthDirection() == TargetFrameInfo::StackGrowsDown;
700
int FrameSetupOpcode = TRI.getCallFrameSetupOpcode();
701
int FrameDestroyOpcode = TRI.getCallFrameDestroyOpcode();
703
for (MachineFunction::iterator BB = Fn.begin(),
704
E = Fn.end(); BB != E; ++BB) {
706
int SPAdjCount = 0; // frame setup / destroy count.
708
int SPAdj = 0; // SP offset due to call frame setup / destroy.
709
if (RS && !FrameIndexVirtualScavenging) RS->enterBasicBlock(BB);
711
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
713
if (I->getOpcode() == FrameSetupOpcode ||
714
I->getOpcode() == FrameDestroyOpcode) {
716
// Track whether we see even pairs of them
717
SPAdjCount += I->getOpcode() == FrameSetupOpcode ? 1 : -1;
719
// Remember how much SP has been adjusted to create the call
721
int Size = I->getOperand(0).getImm();
723
if ((!StackGrowsDown && I->getOpcode() == FrameSetupOpcode) ||
724
(StackGrowsDown && I->getOpcode() == FrameDestroyOpcode))
729
MachineBasicBlock::iterator PrevI = BB->end();
730
if (I != BB->begin()) PrevI = prior(I);
731
TRI.eliminateCallFramePseudoInstr(Fn, *BB, I);
733
// Visit the instructions created by eliminateCallFramePseudoInstr().
734
if (PrevI == BB->end())
735
I = BB->begin(); // The replaced instr was the first in the block.
737
I = llvm::next(PrevI);
741
MachineInstr *MI = I;
743
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i)
744
if (MI->getOperand(i).isFI()) {
745
// Some instructions (e.g. inline asm instructions) can have
746
// multiple frame indices and/or cause eliminateFrameIndex
747
// to insert more than one instruction. We need the register
748
// scavenger to go through all of these instructions so that
749
// it can update its register information. We keep the
750
// iterator at the point before insertion so that we can
751
// revisit them in full.
752
bool AtBeginning = (I == BB->begin());
753
if (!AtBeginning) --I;
755
// If this instruction has a FrameIndex operand, we need to
756
// use that target machine register info object to eliminate
758
TRI.eliminateFrameIndex(MI, SPAdj,
759
FrameIndexVirtualScavenging ? NULL : RS);
761
// Reset the iterator if we were at the beginning of the BB.
771
if (DoIncr && I != BB->end()) ++I;
773
// Update register states.
774
if (RS && !FrameIndexVirtualScavenging && MI) RS->forward(MI);
777
// If we have evenly matched pairs of frame setup / destroy instructions,
778
// make sure the adjustments come out to zero. If we don't have matched
779
// pairs, we can't be sure the missing bit isn't in another basic block
780
// due to a custom inserter playing tricks, so just asserting SPAdj==0
781
// isn't sufficient. See tMOVCC on Thumb1, for example.
782
assert((SPAdjCount || SPAdj == 0) &&
783
"Unbalanced call frame setup / destroy pairs?");
787
/// scavengeFrameVirtualRegs - Replace all frame index virtual registers
788
/// with physical registers. Use the register scavenger to find an
789
/// appropriate register to use.
790
void PEI::scavengeFrameVirtualRegs(MachineFunction &Fn) {
791
// Run through the instructions and find any virtual registers.
792
for (MachineFunction::iterator BB = Fn.begin(),
793
E = Fn.end(); BB != E; ++BB) {
794
RS->enterBasicBlock(BB);
796
unsigned VirtReg = 0;
797
unsigned ScratchReg = 0;
800
// The instruction stream may change in the loop, so check BB->end()
802
for (MachineBasicBlock::iterator I = BB->begin(); I != BB->end(); ) {
803
MachineInstr *MI = I;
805
for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
806
if (MI->getOperand(i).isReg()) {
807
MachineOperand &MO = MI->getOperand(i);
808
unsigned Reg = MO.getReg();
811
if (!TargetRegisterInfo::isVirtualRegister(Reg))
814
++NumVirtualFrameRegs;
816
// Have we already allocated a scratch register for this virtual?
817
if (Reg != VirtReg) {
818
// When we first encounter a new virtual register, it
819
// must be a definition.
820
assert(MI->getOperand(i).isDef() &&
821
"frame index virtual missing def!");
822
// Scavenge a new scratch register
824
const TargetRegisterClass *RC = Fn.getRegInfo().getRegClass(Reg);
825
ScratchReg = RS->scavengeRegister(RC, I, SPAdj);
828
// replace this reference to the virtual register with the
830
assert (ScratchReg && "Missing scratch register!");
831
MI->getOperand(i).setReg(ScratchReg);