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//===-- X86VZeroUpper.cpp - AVX vzeroupper instruction inserter -----------===//
//
// 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 inserts x86 AVX vzeroupper instructions
// before calls to SSE encoded functions. This avoids transition latency
// penalty when tranfering control between AVX encoded instructions and old
// SSE encoding mode.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "x86-codegen"
#include "X86.h"
#include "X86InstrInfo.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/GlobalValue.h"
#include "llvm/Target/TargetInstrInfo.h"
using namespace llvm;
STATISTIC(NumVZU, "Number of vzeroupper instructions inserted");
namespace {
struct VZeroUpperInserter : public MachineFunctionPass {
static char ID;
VZeroUpperInserter() : MachineFunctionPass(ID) {}
virtual bool runOnMachineFunction(MachineFunction &MF);
bool processBasicBlock(MachineFunction &MF, MachineBasicBlock &MBB);
virtual const char *getPassName() const { return "X86 vzeroupper inserter";}
private:
const TargetInstrInfo *TII; // Machine instruction info.
MachineBasicBlock *MBB; // Current basic block
};
char VZeroUpperInserter::ID = 0;
}
FunctionPass *llvm::createX86IssueVZeroUpperPass() {
return new VZeroUpperInserter();
}
/// runOnMachineFunction - Loop over all of the basic blocks, inserting
/// vzero upper instructions before function calls.
bool VZeroUpperInserter::runOnMachineFunction(MachineFunction &MF) {
TII = MF.getTarget().getInstrInfo();
bool Changed = false;
// Process any unreachable blocks in arbitrary order now.
for (MachineFunction::iterator BB = MF.begin(), E = MF.end(); BB != E; ++BB)
Changed |= processBasicBlock(MF, *BB);
return Changed;
}
bool isCallToModuleFn(const MachineInstr *MI) {
assert(MI->getDesc().isCall() && "Isn't a call instruction");
for (int i = 0, e = MI->getNumOperands(); i != e; ++i) {
const MachineOperand &MO = MI->getOperand(i);
if (!MO.isGlobal())
continue;
const GlobalValue *GV = MO.getGlobal();
GlobalValue::LinkageTypes LT = GV->getLinkage();
if (GV->isInternalLinkage(LT) || GV->isPrivateLinkage(LT) ||
(GV->isExternalLinkage(LT) && !GV->isDeclaration()))
return true;
return false;
}
return false;
}
/// processBasicBlock - Loop over all of the instructions in the basic block,
/// inserting vzero upper instructions before function calls.
bool VZeroUpperInserter::processBasicBlock(MachineFunction &MF,
MachineBasicBlock &BB) {
bool Changed = false;
MBB = &BB;
for (MachineBasicBlock::iterator I = BB.begin(); I != BB.end(); ++I) {
MachineInstr *MI = I;
DebugLoc dl = I->getDebugLoc();
// Insert a vzeroupper instruction before each control transfer
// to functions outside this module
if (MI->getDesc().isCall() && !isCallToModuleFn(MI)) {
BuildMI(*MBB, I, dl, TII->get(X86::VZEROUPPER));
++NumVZU;
}
}
return Changed;
}
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