//===-- ARMJITInfo.cpp - Implement the JIT interfaces for the ARM target --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the JIT interfaces for the ARM target.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "jit"
#include "ARMJITInfo.h"
#include "ARMInstrInfo.h"
#include "ARMConstantPoolValue.h"
#include "ARMRelocations.h"
#include "ARMSubtarget.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/JITCodeEmitter.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Memory.h"
#include <cstdlib>
using namespace llvm;
void ARMJITInfo::replaceMachineCodeForFunction(void *Old, void *New) {
report_fatal_error("ARMJITInfo::replaceMachineCodeForFunction");
}
/// JITCompilerFunction - This contains the address of the JIT function used to
/// compile a function lazily.
static TargetJITInfo::JITCompilerFn JITCompilerFunction;
// Get the ASMPREFIX for the current host. This is often '_'.
#ifndef __USER_LABEL_PREFIX__
#define __USER_LABEL_PREFIX__
#endif
#define GETASMPREFIX2(X) #X
#define GETASMPREFIX(X) GETASMPREFIX2(X)
#define ASMPREFIX GETASMPREFIX(__USER_LABEL_PREFIX__)
// CompilationCallback stub - We can't use a C function with inline assembly in
// it, because the prolog/epilog inserted by GCC won't work for us. (We need
// to preserve more context and manipulate the stack directly). Instead,
// write our own wrapper, which does things our way, so we have complete
// control over register saving and restoring.
extern "C" {
#if defined(__arm__)
void ARMCompilationCallback();
asm(
".text\n"
".align 2\n"
".globl " ASMPREFIX "ARMCompilationCallback\n"
ASMPREFIX "ARMCompilationCallback:\n"
// Save caller saved registers since they may contain stuff
// for the real target function right now. We have to act as if this
// whole compilation callback doesn't exist as far as the caller is
// concerned, so we can't just preserve the callee saved regs.
"stmdb sp!, {r0, r1, r2, r3, lr}\n"
#if (defined(__VFP_FP__) && !defined(__SOFTFP__))
"fstmfdd sp!, {d0, d1, d2, d3, d4, d5, d6, d7}\n"
#endif
// The LR contains the address of the stub function on entry.
// pass it as the argument to the C part of the callback
"mov r0, lr\n"
"sub sp, sp, #4\n"
// Call the C portion of the callback
"bl " ASMPREFIX "ARMCompilationCallbackC\n"
"add sp, sp, #4\n"
// Restoring the LR to the return address of the function that invoked
// the stub and de-allocating the stack space for it requires us to
// swap the two saved LR values on the stack, as they're backwards
// for what we need since the pop instruction has a pre-determined
// order for the registers.
// +--------+
// 0 | LR | Original return address
// +--------+
// 1 | LR | Stub address (start of stub)
// 2-5 | R3..R0 | Saved registers (we need to preserve all regs)
// 6-20 | D0..D7 | Saved VFP registers
// +--------+
//
#if (defined(__VFP_FP__) && !defined(__SOFTFP__))
// Restore VFP caller-saved registers.
"fldmfdd sp!, {d0, d1, d2, d3, d4, d5, d6, d7}\n"
#endif
//
// We need to exchange the values in slots 0 and 1 so we can
// return to the address in slot 1 with the address in slot 0
// restored to the LR.
"ldr r0, [sp,#20]\n"
"ldr r1, [sp,#16]\n"
"str r1, [sp,#20]\n"
"str r0, [sp,#16]\n"
// Return to the (newly modified) stub to invoke the real function.
// The above twiddling of the saved return addresses allows us to
// deallocate everything, including the LR the stub saved, with two
// updating load instructions.
"ldmia sp!, {r0, r1, r2, r3, lr}\n"
"ldr pc, [sp], #4\n"
);
#else // Not an ARM host
void ARMCompilationCallback() {
llvm_unreachable("Cannot call ARMCompilationCallback() on a non-ARM arch!");
}
#endif
}
/// ARMCompilationCallbackC - This is the target-specific function invoked
/// by the function stub when we did not know the real target of a call.
/// This function must locate the start of the stub or call site and pass
/// it into the JIT compiler function.
extern "C" void ARMCompilationCallbackC(intptr_t StubAddr) {
// Get the address of the compiled code for this function.
intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)StubAddr);
// Rewrite the call target... so that we don't end up here every time we
// execute the call. We're replacing the first two instructions of the
// stub with:
// ldr pc, [pc,#-4]
// <addr>
if (!sys::Memory::setRangeWritable((void*)StubAddr, 8)) {
llvm_unreachable("ERROR: Unable to mark stub writable");
}
*(intptr_t *)StubAddr = 0xe51ff004; // ldr pc, [pc, #-4]
*(intptr_t *)(StubAddr+4) = NewVal;
if (!sys::Memory::setRangeExecutable((void*)StubAddr, 8)) {
llvm_unreachable("ERROR: Unable to mark stub executable");
}
}
TargetJITInfo::LazyResolverFn
ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) {
JITCompilerFunction = F;
return ARMCompilationCallback;
}
void *ARMJITInfo::emitGlobalValueIndirectSym(const GlobalValue *GV, void *Ptr,
JITCodeEmitter &JCE) {
uint8_t Buffer[4];
uint8_t *Cur = Buffer;
MachineCodeEmitter::emitWordLEInto(Cur, (intptr_t)Ptr);
void *PtrAddr = JCE.allocIndirectGV(
GV, Buffer, sizeof(Buffer), /*Alignment=*/4);
addIndirectSymAddr(Ptr, (intptr_t)PtrAddr);
return PtrAddr;
}
TargetJITInfo::StubLayout ARMJITInfo::getStubLayout() {
// The stub contains up to 3 4-byte instructions, aligned at 4 bytes, and a
// 4-byte address. See emitFunctionStub for details.
StubLayout Result = {16, 4};
return Result;
}
void *ARMJITInfo::emitFunctionStub(const Function* F, void *Fn,
JITCodeEmitter &JCE) {
void *Addr;
// If this is just a call to an external function, emit a branch instead of a
// call. The code is the same except for one bit of the last instruction.
if (Fn != (void*)(intptr_t)ARMCompilationCallback) {
// Branch to the corresponding function addr.
if (IsPIC) {
// The stub is 16-byte size and 4-aligned.
intptr_t LazyPtr = getIndirectSymAddr(Fn);
if (!LazyPtr) {
// In PIC mode, the function stub is loading a lazy-ptr.
LazyPtr= (intptr_t)emitGlobalValueIndirectSym((GlobalValue*)F, Fn, JCE);
DEBUG(if (F)
errs() << "JIT: Indirect symbol emitted at [" << LazyPtr
<< "] for GV '" << F->getName() << "'\n";
else
errs() << "JIT: Stub emitted at [" << LazyPtr
<< "] for external function at '" << Fn << "'\n");
}
JCE.emitAlignment(4);
Addr = (void*)JCE.getCurrentPCValue();
if (!sys::Memory::setRangeWritable(Addr, 16)) {
llvm_unreachable("ERROR: Unable to mark stub writable");
}
JCE.emitWordLE(0xe59fc004); // ldr ip, [pc, #+4]
JCE.emitWordLE(0xe08fc00c); // L_func$scv: add ip, pc, ip
JCE.emitWordLE(0xe59cf000); // ldr pc, [ip]
JCE.emitWordLE(LazyPtr - (intptr_t(Addr)+4+8)); // func - (L_func$scv+8)
sys::Memory::InvalidateInstructionCache(Addr, 16);
if (!sys::Memory::setRangeExecutable(Addr, 16)) {
llvm_unreachable("ERROR: Unable to mark stub executable");
}
} else {
// The stub is 8-byte size and 4-aligned.
JCE.emitAlignment(4);
Addr = (void*)JCE.getCurrentPCValue();
if (!sys::Memory::setRangeWritable(Addr, 8)) {
llvm_unreachable("ERROR: Unable to mark stub writable");
}
JCE.emitWordLE(0xe51ff004); // ldr pc, [pc, #-4]
JCE.emitWordLE((intptr_t)Fn); // addr of function
sys::Memory::InvalidateInstructionCache(Addr, 8);
if (!sys::Memory::setRangeExecutable(Addr, 8)) {
llvm_unreachable("ERROR: Unable to mark stub executable");
}
}
} else {
// The compilation callback will overwrite the first two words of this
// stub with indirect branch instructions targeting the compiled code.
// This stub sets the return address to restart the stub, so that
// the new branch will be invoked when we come back.
//
// Branch and link to the compilation callback.
// The stub is 16-byte size and 4-byte aligned.
JCE.emitAlignment(4);
Addr = (void*)JCE.getCurrentPCValue();
if (!sys::Memory::setRangeWritable(Addr, 16)) {
llvm_unreachable("ERROR: Unable to mark stub writable");
}
// Save LR so the callback can determine which stub called it.
// The compilation callback is responsible for popping this prior
// to returning.
JCE.emitWordLE(0xe92d4000); // push {lr}
// Set the return address to go back to the start of this stub.
JCE.emitWordLE(0xe24fe00c); // sub lr, pc, #12
// Invoke the compilation callback.
JCE.emitWordLE(0xe51ff004); // ldr pc, [pc, #-4]
// The address of the compilation callback.
JCE.emitWordLE((intptr_t)ARMCompilationCallback);
sys::Memory::InvalidateInstructionCache(Addr, 16);
if (!sys::Memory::setRangeExecutable(Addr, 16)) {
llvm_unreachable("ERROR: Unable to mark stub executable");
}
}
return Addr;
}
intptr_t ARMJITInfo::resolveRelocDestAddr(MachineRelocation *MR) const {
ARM::RelocationType RT = (ARM::RelocationType)MR->getRelocationType();
switch (RT) {
default:
return (intptr_t)(MR->getResultPointer());
case ARM::reloc_arm_pic_jt:
// Destination address - jump table base.
return (intptr_t)(MR->getResultPointer()) - MR->getConstantVal();
case ARM::reloc_arm_jt_base:
// Jump table base address.
return getJumpTableBaseAddr(MR->getJumpTableIndex());
case ARM::reloc_arm_cp_entry:
case ARM::reloc_arm_vfp_cp_entry:
// Constant pool entry address.
return getConstantPoolEntryAddr(MR->getConstantPoolIndex());
case ARM::reloc_arm_machine_cp_entry: {
ARMConstantPoolValue *ACPV = (ARMConstantPoolValue*)MR->getConstantVal();
assert((!ACPV->hasModifier() && !ACPV->mustAddCurrentAddress()) &&
"Can't handle this machine constant pool entry yet!");
intptr_t Addr = (intptr_t)(MR->getResultPointer());
Addr -= getPCLabelAddr(ACPV->getLabelId()) + ACPV->getPCAdjustment();
return Addr;
}
}
}
/// relocate - Before the JIT can run a block of code that has been emitted,
/// it must rewrite the code to contain the actual addresses of any
/// referenced global symbols.
void ARMJITInfo::relocate(void *Function, MachineRelocation *MR,
unsigned NumRelocs, unsigned char* GOTBase) {
for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
intptr_t ResultPtr = resolveRelocDestAddr(MR);
switch ((ARM::RelocationType)MR->getRelocationType()) {
case ARM::reloc_arm_cp_entry:
case ARM::reloc_arm_vfp_cp_entry:
case ARM::reloc_arm_relative: {
// It is necessary to calculate the correct PC relative value. We
// subtract the base addr from the target addr to form a byte offset.
ResultPtr = ResultPtr - (intptr_t)RelocPos - 8;
// If the result is positive, set bit U(23) to 1.
if (ResultPtr >= 0)
*((intptr_t*)RelocPos) |= 1 << ARMII::U_BitShift;
else {
// Otherwise, obtain the absolute value and set bit U(23) to 0.
*((intptr_t*)RelocPos) &= ~(1 << ARMII::U_BitShift);
ResultPtr = - ResultPtr;
}
// Set the immed value calculated.
// VFP immediate offset is multiplied by 4.
if (MR->getRelocationType() == ARM::reloc_arm_vfp_cp_entry)
ResultPtr = ResultPtr >> 2;
*((intptr_t*)RelocPos) |= ResultPtr;
// Set register Rn to PC.
*((intptr_t*)RelocPos) |=
getARMRegisterNumbering(ARM::PC) << ARMII::RegRnShift;
break;
}
case ARM::reloc_arm_pic_jt:
case ARM::reloc_arm_machine_cp_entry:
case ARM::reloc_arm_absolute: {
// These addresses have already been resolved.
*((intptr_t*)RelocPos) |= (intptr_t)ResultPtr;
break;
}
case ARM::reloc_arm_branch: {
// It is necessary to calculate the correct value of signed_immed_24
// field. We subtract the base addr from the target addr to form a
// byte offset, which must be inside the range -33554432 and +33554428.
// Then, we set the signed_immed_24 field of the instruction to bits
// [25:2] of the byte offset. More details ARM-ARM p. A4-11.
ResultPtr = ResultPtr - (intptr_t)RelocPos - 8;
ResultPtr = (ResultPtr & 0x03FFFFFC) >> 2;
assert(ResultPtr >= -33554432 && ResultPtr <= 33554428);
*((intptr_t*)RelocPos) |= ResultPtr;
break;
}
case ARM::reloc_arm_jt_base: {
// JT base - (instruction addr + 8)
ResultPtr = ResultPtr - (intptr_t)RelocPos - 8;
*((intptr_t*)RelocPos) |= ResultPtr;
break;
}
case ARM::reloc_arm_movw: {
ResultPtr = ResultPtr & 0xFFFF;
*((intptr_t*)RelocPos) |= ResultPtr & 0xFFF;
*((intptr_t*)RelocPos) |= ((ResultPtr >> 12) & 0xF) << 16;
break;
}
case ARM::reloc_arm_movt: {
ResultPtr = (ResultPtr >> 16) & 0xFFFF;
*((intptr_t*)RelocPos) |= ResultPtr & 0xFFF;
*((intptr_t*)RelocPos) |= ((ResultPtr >> 12) & 0xF) << 16;
break;
}
}
}
}