llvm/lib/CodeGen/PatchableFunction.cpp
2016-04-19 06:25:02 +00:00

72 lines
2.4 KiB
C++

//===-- PatchableFunction.cpp - Patchable prologues for LLVM -------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements edits function bodies in place to support the
// "patchable-function" attribute.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Target/TargetSubtargetInfo.h"
using namespace llvm;
namespace {
struct PatchableFunction : public MachineFunctionPass {
static char ID; // Pass identification, replacement for typeid
PatchableFunction() : MachineFunctionPass(ID) {
initializePatchableFunctionPass(*PassRegistry::getPassRegistry());
}
bool runOnMachineFunction(MachineFunction &F) override;
MachineFunctionProperties getRequiredProperties() const override {
return MachineFunctionProperties().set(
MachineFunctionProperties::Property::AllVRegsAllocated);
}
};
}
bool PatchableFunction::runOnMachineFunction(MachineFunction &MF) {
if (!MF.getFunction()->hasFnAttribute("patchable-function"))
return false;
#ifndef NDEBUG
Attribute PatchAttr = MF.getFunction()->getFnAttribute("patchable-function");
StringRef PatchType = PatchAttr.getValueAsString();
assert(PatchType == "prologue-short-redirect" && "Only possibility today!");
#endif
auto &FirstMBB = *MF.begin();
auto &FirstMI = *FirstMBB.begin();
auto *TII = MF.getSubtarget().getInstrInfo();
auto MIB = BuildMI(FirstMBB, FirstMBB.begin(), FirstMI.getDebugLoc(),
TII->get(TargetOpcode::PATCHABLE_OP))
.addImm(2)
.addImm(FirstMI.getOpcode());
for (auto &MO : FirstMI.operands())
MIB.addOperand(MO);
FirstMI.eraseFromParent();
MF.ensureAlignment(4);
return true;
}
char PatchableFunction::ID = 0;
char &llvm::PatchableFunctionID = PatchableFunction::ID;
INITIALIZE_PASS(PatchableFunction, "patchable-function",
"Implement the 'patchable-function' attribute", false, false)