def FeatureLeaForSP : SubtargetFeature<"lea-sp", "UseLeaForSP", "true",
"Use LEA for adjusting the stack pointer">;
def FeatureSlowDivide : SubtargetFeature<"idiv-to-divb",
- "HasSlowDivide", "true",
- "Use small divide for positive values less than 256">;
-def FeaturePadShortFunctions : SubtargetFeature<"pad-short-functions",
- "PadShortFunctions", "true",
- "Pad short functions">;
+ "HasSlowDivide", "true",
+ "Use small divide for positive values less than 256">;
//===----------------------------------------------------------------------===//
// X86 processors supported.
FeatureSlowBTMem]>;
def : AtomProc<"atom", [ProcIntelAtom, FeatureSSSE3, FeatureCMPXCHG16B,
FeatureMOVBE, FeatureSlowBTMem, FeatureLeaForSP,
- FeatureSlowDivide, FeaturePadShortFunctions]>;
+ FeatureSlowDivide]>;
// "Arrandale" along with corei3 and corei5
def : Proc<"corei7", [FeatureSSE42, FeatureCMPXCHG16B,
FeatureSlowBTMem, FeatureFastUAMem,
+++ /dev/null
-//===-------- X86PadShortFunction.cpp - pad short functions -----------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file defines the pass which will pad short functions to prevent
-// a stall if a function returns before the return address is ready. This
-// is needed for some Intel Atom processors.
-//
-//===----------------------------------------------------------------------===//
-
-#include <map>
-#include <algorithm>
-
-#define DEBUG_TYPE "x86-pad-short-functions"
-#include "X86.h"
-#include "X86InstrInfo.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/CodeGen/MachineFunctionPass.h"
-#include "llvm/CodeGen/MachineInstrBuilder.h"
-#include "llvm/CodeGen/MachineRegisterInfo.h"
-#include "llvm/CodeGen/Passes.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-#include "llvm/Target/TargetInstrInfo.h"
-using namespace llvm;
-
-STATISTIC(NumBBsPadded, "Number of basic blocks padded");
-
-namespace {
- struct PadShortFunc : public MachineFunctionPass {
- static char ID;
- PadShortFunc() : MachineFunctionPass(ID)
- , Threshold(4)
- {}
-
- virtual bool runOnMachineFunction(MachineFunction &MF);
-
- virtual const char *getPassName() const
- {
- return "X86 Atom pad short functions";
- }
-
- private:
- bool addPadding(MachineFunction &MF,
- MachineBasicBlock &MBB,
- MachineBasicBlock::iterator &MBBI,
- unsigned int NOOPsToAdd);
-
- void findReturn(MachineFunction &MF,
- MachineBasicBlock &MBB,
- unsigned int Cycles);
-
- bool cyclesUntilReturn(MachineFunction &MF,
- MachineBasicBlock &MBB,
- unsigned int &Cycles,
- MachineBasicBlock::iterator *Location = 0);
-
- const unsigned int Threshold;
- std::map<int, unsigned int> ReturnBBs;
- };
-
- char PadShortFunc::ID = 0;
-}
-
-FunctionPass *llvm::createX86PadShortFunctions() {
- return new PadShortFunc();
-}
-
-/// runOnMachineFunction - Loop over all of the basic blocks, inserting
-/// NOOP instructions before early exits.
-bool PadShortFunc::runOnMachineFunction(MachineFunction &MF) {
- // Process all basic blocks.
- ReturnBBs.clear();
-
- // Search through basic blocks and mark the ones that have early returns
- findReturn(MF, *MF.begin(), 0);
-
- int BBNum;
- MachineBasicBlock::iterator ReturnLoc;
- MachineBasicBlock *MBB;
-
- unsigned int Cycles = 0;
- unsigned int BBCycles;
-
- // Pad the identified basic blocks with NOOPs
- for (std::map<int, unsigned int>::iterator I = ReturnBBs.begin();
- I != ReturnBBs.end(); ++I) {
- BBNum = I->first;
- Cycles = I->second;
-
- if (Cycles < Threshold) {
- MBB = MF.getBlockNumbered(BBNum);
- if (!cyclesUntilReturn(MF, *MBB, BBCycles, &ReturnLoc))
- continue;
-
- addPadding(MF, *MBB, ReturnLoc, Threshold - Cycles);
- NumBBsPadded++;
- }
- }
-
- return false;
-}
-
-/// findReturn - Starting at MBB, follow control flow and add all
-/// basic blocks that contain a return to ReturnBBs.
-void PadShortFunc::findReturn(MachineFunction &MF,
- MachineBasicBlock &MBB,
- unsigned int Cycles)
-{
- // If this BB has a return, note how many cycles it takes to get there.
- bool hasReturn = cyclesUntilReturn(MF, MBB, Cycles);
- if (Cycles >= Threshold)
- return;
-
- if (hasReturn) {
- int BBNum = MBB.getNumber();
- ReturnBBs[BBNum] = std::max(ReturnBBs[BBNum], Cycles);
-
- return;
- }
-
- // Follow branches in BB and look for returns
- for (MachineBasicBlock::succ_iterator I = MBB.succ_begin();
- I != MBB.succ_end(); ++I) {
- findReturn(MF, **I, Cycles);
- }
-}
-
-/// cyclesUntilReturn - if the MBB has a return instruction, set Location to
-/// to the instruction and return true. Return false otherwise.
-/// Cycles will be incremented by the number of cycles taken to reach the
-/// return or the end of the BB, whichever occurs first.
-bool PadShortFunc::cyclesUntilReturn(MachineFunction &MF,
- MachineBasicBlock &MBB,
- unsigned int &Cycles,
- MachineBasicBlock::iterator *Location)
-{
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
- const TargetMachine &Target = MF.getTarget();
-
- for (MachineBasicBlock::iterator MBBI = MBB.begin(); MBBI != MBB.end();
- ++MBBI) {
- MachineInstr *MI = MBBI;
- // Mark basic blocks with a return instruction. Calls to other functions
- // do not count because the called function will be padded, if necessary
- if (MI->isReturn() && !MI->isCall()) {
- if (Location)
- *Location = MBBI;
- return true;
- }
-
- Cycles += TII.getInstrLatency(Target.getInstrItineraryData(), MI);
- }
-
- return false;
-}
-
-/// addPadding - Add the given number of NOOP instructions to the function
-/// right before the return at MBBI
-bool PadShortFunc::addPadding(MachineFunction &MF,
- MachineBasicBlock &MBB,
- MachineBasicBlock::iterator &MBBI,
- unsigned int NOOPsToAdd)
-{
- const TargetInstrInfo &TII = *MF.getTarget().getInstrInfo();
-
- DebugLoc DL = MBBI->getDebugLoc();
-
- while (NOOPsToAdd-- > 0) {
- // Since Atom has two instruction execution ports,
- // the code emits two noops, which will be executed in parallell
- // during one cycle.
- BuildMI(MBB, MBBI, DL, TII.get(X86::NOOP));
- BuildMI(MBB, MBBI, DL, TII.get(X86::NOOP));
- }
-
- return true;
-}
-
projects / oota-llvm.git / commitdiff