1 //===-- ARMJITInfo.cpp - Implement the JIT interfaces for the ARM target --===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This file implements the JIT interfaces for the ARM target. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #define DEBUG_TYPE "jit" 15 #include "ARMJITInfo.h" 16 #include "ARMInstrInfo.h" 17 #include "ARMConstantPoolValue.h" 18 #include "ARMAddressingModes.h" 19 #include "ARMRelocations.h" 20 #include "ARMSubtarget.h" 21 #include "llvm/Function.h" 22 #include "llvm/CodeGen/JITCodeEmitter.h" 23 #include "llvm/Support/Debug.h" 24 #include "llvm/Support/ErrorHandling.h" 25 #include "llvm/Support/raw_ostream.h" 26 #include "llvm/Support/Memory.h" 27 #include <cstdlib> 28 using namespace llvm; 29 30 void ARMJITInfo::replaceMachineCodeForFunction(void *Old, void *New) { 31 report_fatal_error("ARMJITInfo::replaceMachineCodeForFunction"); 32 } 33 34 /// JITCompilerFunction - This contains the address of the JIT function used to 35 /// compile a function lazily. 36 static TargetJITInfo::JITCompilerFn JITCompilerFunction; 37 38 // Get the ASMPREFIX for the current host. This is often '_'. 39 #ifndef __USER_LABEL_PREFIX__ 40 #define __USER_LABEL_PREFIX__ 41 #endif 42 #define GETASMPREFIX2(X) #X 43 #define GETASMPREFIX(X) GETASMPREFIX2(X) 44 #define ASMPREFIX GETASMPREFIX(__USER_LABEL_PREFIX__) 45 46 // CompilationCallback stub - We can't use a C function with inline assembly in 47 // it, because the prolog/epilog inserted by GCC won't work for us. (We need 48 // to preserve more context and manipulate the stack directly). Instead, 49 // write our own wrapper, which does things our way, so we have complete 50 // control over register saving and restoring. 51 extern "C" { 52 #if defined(__arm__) && !defined(ANDROID) 53 void ARMCompilationCallback(); 54 asm( 55 ".text\n" 56 ".align 2\n" 57 ".globl " ASMPREFIX "ARMCompilationCallback\n" 58 ASMPREFIX "ARMCompilationCallback:\n" 59 // Save caller saved registers since they may contain stuff 60 // for the real target function right now. We have to act as if this 61 // whole compilation callback doesn't exist as far as the caller is 62 // concerned, so we can't just preserve the callee saved regs. 63 "stmdb sp!, {r0, r1, r2, r3, lr}\n" 64 #if (defined(__VFP_FP__) && !defined(__SOFTFP__)) 65 "fstmfdd sp!, {d0, d1, d2, d3, d4, d5, d6, d7}\n" 66 #endif 67 // The LR contains the address of the stub function on entry. 68 // pass it as the argument to the C part of the callback 69 "mov r0, lr\n" 70 "sub sp, sp, #4\n" 71 // Call the C portion of the callback 72 "bl " ASMPREFIX "ARMCompilationCallbackC\n" 73 "add sp, sp, #4\n" 74 // Restoring the LR to the return address of the function that invoked 75 // the stub and de-allocating the stack space for it requires us to 76 // swap the two saved LR values on the stack, as they're backwards 77 // for what we need since the pop instruction has a pre-determined 78 // order for the registers. 79 // +--------+ 80 // 0 | LR | Original return address 81 // +--------+ 82 // 1 | LR | Stub address (start of stub) 83 // 2-5 | R3..R0 | Saved registers (we need to preserve all regs) 84 // 6-20 | D0..D7 | Saved VFP registers 85 // +--------+ 86 // 87 #if (defined(__VFP_FP__) && !defined(__SOFTFP__)) 88 // Restore VFP caller-saved registers. 89 "fldmfdd sp!, {d0, d1, d2, d3, d4, d5, d6, d7}\n" 90 #endif 91 // 92 // We need to exchange the values in slots 0 and 1 so we can 93 // return to the address in slot 1 with the address in slot 0 94 // restored to the LR. 95 "ldr r0, [sp,#20]\n" 96 "ldr r1, [sp,#16]\n" 97 "str r1, [sp,#20]\n" 98 "str r0, [sp,#16]\n" 99 // Return to the (newly modified) stub to invoke the real function. 100 // The above twiddling of the saved return addresses allows us to 101 // deallocate everything, including the LR the stub saved, with two 102 // updating load instructions. 103 "ldmia sp!, {r0, r1, r2, r3, lr}\n" 104 "ldr pc, [sp], #4\n" 105 ); 106 #else // Not an ARM host 107 void ARMCompilationCallback() { 108 llvm_unreachable("Cannot call ARMCompilationCallback() on a non-ARM arch!"); 109 } 110 #endif 111 } 112 113 /// ARMCompilationCallbackC - This is the target-specific function invoked 114 /// by the function stub when we did not know the real target of a call. 115 /// This function must locate the start of the stub or call site and pass 116 /// it into the JIT compiler function. 117 extern "C" void ARMCompilationCallbackC(intptr_t StubAddr) { 118 // Get the address of the compiled code for this function. 119 intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)StubAddr); 120 121 // Rewrite the call target... so that we don't end up here every time we 122 // execute the call. We're replacing the first two instructions of the 123 // stub with: 124 // ldr pc, [pc,#-4] 125 // <addr> 126 if (!sys::Memory::setRangeWritable((void*)StubAddr, 8)) { 127 llvm_unreachable("ERROR: Unable to mark stub writable"); 128 } 129 *(intptr_t *)StubAddr = 0xe51ff004; // ldr pc, [pc, #-4] 130 *(intptr_t *)(StubAddr+4) = NewVal; 131 if (!sys::Memory::setRangeExecutable((void*)StubAddr, 8)) { 132 llvm_unreachable("ERROR: Unable to mark stub executable"); 133 } 134 } 135 136 TargetJITInfo::LazyResolverFn 137 ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) { 138 JITCompilerFunction = F; 139 return ARMCompilationCallback; 140 } 141 142 void *ARMJITInfo::emitGlobalValueIndirectSym(const GlobalValue *GV, void *Ptr, 143 JITCodeEmitter &JCE) { 144 uint8_t Buffer[4]; 145 uint8_t *Cur = Buffer; 146 MachineCodeEmitter::emitWordLEInto(Cur, (intptr_t)Ptr); 147 void *PtrAddr = JCE.allocIndirectGV( 148 GV, Buffer, sizeof(Buffer), /*Alignment=*/4); 149 addIndirectSymAddr(Ptr, (intptr_t)PtrAddr); 150 return PtrAddr; 151 } 152 153 TargetJITInfo::StubLayout ARMJITInfo::getStubLayout() { 154 // The stub contains up to 3 4-byte instructions, aligned at 4 bytes, and a 155 // 4-byte address. See emitFunctionStub for details. 156 StubLayout Result = {16, 4}; 157 return Result; 158 } 159 160 void *ARMJITInfo::emitFunctionStub(const Function* F, void *Fn, 161 JITCodeEmitter &JCE) { 162 void *Addr; 163 // If this is just a call to an external function, emit a branch instead of a 164 // call. The code is the same except for one bit of the last instruction. 165 if (Fn != (void*)(intptr_t)ARMCompilationCallback) { 166 // Branch to the corresponding function addr. 167 if (IsPIC) { 168 // The stub is 16-byte size and 4-aligned. 169 intptr_t LazyPtr = getIndirectSymAddr(Fn); 170 if (!LazyPtr) { 171 // In PIC mode, the function stub is loading a lazy-ptr. 172 LazyPtr= (intptr_t)emitGlobalValueIndirectSym((GlobalValue*)F, Fn, JCE); 173 DEBUG(if (F) 174 errs() << "JIT: Indirect symbol emitted at [" << LazyPtr 175 << "] for GV '" << F->getName() << "'\n"; 176 else 177 errs() << "JIT: Stub emitted at [" << LazyPtr 178 << "] for external function at '" << Fn << "'\n"); 179 } 180 JCE.emitAlignment(4); 181 Addr = (void*)JCE.getCurrentPCValue(); 182 if (!sys::Memory::setRangeWritable(Addr, 16)) { 183 llvm_unreachable("ERROR: Unable to mark stub writable"); 184 } 185 JCE.emitWordLE(0xe59fc004); // ldr ip, [pc, #+4] 186 JCE.emitWordLE(0xe08fc00c); // L_func$scv: add ip, pc, ip 187 JCE.emitWordLE(0xe59cf000); // ldr pc, [ip] 188 JCE.emitWordLE(LazyPtr - (intptr_t(Addr)+4+8)); // func - (L_func$scv+8) 189 sys::Memory::InvalidateInstructionCache(Addr, 16); 190 if (!sys::Memory::setRangeExecutable(Addr, 16)) { 191 llvm_unreachable("ERROR: Unable to mark stub executable"); 192 } 193 } else { 194 // The stub is 8-byte size and 4-aligned. 195 JCE.emitAlignment(4); 196 Addr = (void*)JCE.getCurrentPCValue(); 197 if (!sys::Memory::setRangeWritable(Addr, 8)) { 198 llvm_unreachable("ERROR: Unable to mark stub writable"); 199 } 200 JCE.emitWordLE(0xe51ff004); // ldr pc, [pc, #-4] 201 JCE.emitWordLE((intptr_t)Fn); // addr of function 202 sys::Memory::InvalidateInstructionCache(Addr, 8); 203 if (!sys::Memory::setRangeExecutable(Addr, 8)) { 204 llvm_unreachable("ERROR: Unable to mark stub executable"); 205 } 206 } 207 } else { 208 // The compilation callback will overwrite the first two words of this 209 // stub with indirect branch instructions targeting the compiled code. 210 // This stub sets the return address to restart the stub, so that 211 // the new branch will be invoked when we come back. 212 // 213 // Branch and link to the compilation callback. 214 // The stub is 16-byte size and 4-byte aligned. 215 JCE.emitAlignment(4); 216 Addr = (void*)JCE.getCurrentPCValue(); 217 if (!sys::Memory::setRangeWritable(Addr, 16)) { 218 llvm_unreachable("ERROR: Unable to mark stub writable"); 219 } 220 // Save LR so the callback can determine which stub called it. 221 // The compilation callback is responsible for popping this prior 222 // to returning. 223 JCE.emitWordLE(0xe92d4000); // push {lr} 224 // Set the return address to go back to the start of this stub. 225 JCE.emitWordLE(0xe24fe00c); // sub lr, pc, #12 226 // Invoke the compilation callback. 227 JCE.emitWordLE(0xe51ff004); // ldr pc, [pc, #-4] 228 // The address of the compilation callback. 229 JCE.emitWordLE((intptr_t)ARMCompilationCallback); 230 sys::Memory::InvalidateInstructionCache(Addr, 16); 231 if (!sys::Memory::setRangeExecutable(Addr, 16)) { 232 llvm_unreachable("ERROR: Unable to mark stub executable"); 233 } 234 } 235 236 return Addr; 237 } 238 239 intptr_t ARMJITInfo::resolveRelocDestAddr(MachineRelocation *MR) const { 240 ARM::RelocationType RT = (ARM::RelocationType)MR->getRelocationType(); 241 switch (RT) { 242 default: 243 return (intptr_t)(MR->getResultPointer()); 244 case ARM::reloc_arm_pic_jt: 245 // Destination address - jump table base. 246 return (intptr_t)(MR->getResultPointer()) - MR->getConstantVal(); 247 case ARM::reloc_arm_jt_base: 248 // Jump table base address. 249 return getJumpTableBaseAddr(MR->getJumpTableIndex()); 250 case ARM::reloc_arm_cp_entry: 251 case ARM::reloc_arm_vfp_cp_entry: 252 case ARM::reloc_arm_so_imm_cp_entry: 253 // Constant pool entry address. 254 return getConstantPoolEntryAddr(MR->getConstantPoolIndex()); 255 case ARM::reloc_arm_machine_cp_entry: { 256 ARMConstantPoolValue *ACPV = (ARMConstantPoolValue*)MR->getConstantVal(); 257 assert((!ACPV->hasModifier() && !ACPV->mustAddCurrentAddress()) && 258 "Can't handle this machine constant pool entry yet!"); 259 intptr_t Addr = (intptr_t)(MR->getResultPointer()); 260 Addr -= getPCLabelAddr(ACPV->getLabelId()) + ACPV->getPCAdjustment(); 261 return Addr; 262 } 263 } 264 } 265 266 /// relocate - Before the JIT can run a block of code that has been emitted, 267 /// it must rewrite the code to contain the actual addresses of any 268 /// referenced global symbols. 269 void ARMJITInfo::relocate(void *Function, MachineRelocation *MR, 270 unsigned NumRelocs, unsigned char* GOTBase) { 271 for (unsigned i = 0; i != NumRelocs; ++i, ++MR) { 272 void *RelocPos = (char*)Function + MR->getMachineCodeOffset(); 273 intptr_t ResultPtr = resolveRelocDestAddr(MR); 274 switch ((ARM::RelocationType)MR->getRelocationType()) { 275 case ARM::reloc_arm_cp_entry: 276 case ARM::reloc_arm_vfp_cp_entry: 277 case ARM::reloc_arm_relative: { 278 // It is necessary to calculate the correct PC relative value. We 279 // subtract the base addr from the target addr to form a byte offset. 280 ResultPtr = ResultPtr - (intptr_t)RelocPos - 8; 281 // If the result is positive, set bit U(23) to 1. 282 if (ResultPtr >= 0) 283 *((intptr_t*)RelocPos) |= 1 << ARMII::U_BitShift; 284 else { 285 // Otherwise, obtain the absolute value and set bit U(23) to 0. 286 *((intptr_t*)RelocPos) &= ~(1 << ARMII::U_BitShift); 287 ResultPtr = - ResultPtr; 288 } 289 // Set the immed value calculated. 290 // VFP immediate offset is multiplied by 4. 291 if (MR->getRelocationType() == ARM::reloc_arm_vfp_cp_entry) 292 ResultPtr = ResultPtr >> 2; 293 *((intptr_t*)RelocPos) |= ResultPtr; 294 // Set register Rn to PC. 295 *((intptr_t*)RelocPos) |= 296 getARMRegisterNumbering(ARM::PC) << ARMII::RegRnShift; 297 break; 298 } 299 case ARM::reloc_arm_so_imm_cp_entry: { 300 ResultPtr = ResultPtr - (intptr_t)RelocPos - 8; 301 // If the result is positive, set bit U(23) to 1. 302 if (ResultPtr >= 0) 303 *((intptr_t*)RelocPos) |= 1 << ARMII::U_BitShift; 304 else { 305 // Otherwise, obtain the absolute value and set bit U(23) to 0. 306 *((intptr_t*)RelocPos) &= ~(1 << ARMII::U_BitShift); 307 // FIXME: Also set bit 22 to 1 since 'sub' instruction is going to be used. 308 *((intptr_t*)RelocPos) |= 1 << 22; 309 ResultPtr = - ResultPtr; 310 } 311 312 int SoImmVal = ARM_AM::getSOImmVal(ResultPtr); 313 assert(SoImmVal != -1 && "Not a valid so_imm value!"); 314 *((intptr_t*)RelocPos) |= (ARM_AM::getSOImmValRot((unsigned)SoImmVal) >> 1) 315 << ARMII::SoRotImmShift; 316 *((intptr_t*)RelocPos) |= ARM_AM::getSOImmValImm((unsigned)SoImmVal); 317 // Set register Rn to PC. 318 *((intptr_t*)RelocPos) |= 319 getARMRegisterNumbering(ARM::PC) << ARMII::RegRnShift; 320 break; 321 } 322 case ARM::reloc_arm_pic_jt: 323 case ARM::reloc_arm_machine_cp_entry: 324 case ARM::reloc_arm_absolute: { 325 // These addresses have already been resolved. 326 *((intptr_t*)RelocPos) |= (intptr_t)ResultPtr; 327 break; 328 } 329 case ARM::reloc_arm_branch: { 330 // It is necessary to calculate the correct value of signed_immed_24 331 // field. We subtract the base addr from the target addr to form a 332 // byte offset, which must be inside the range -33554432 and +33554428. 333 // Then, we set the signed_immed_24 field of the instruction to bits 334 // [25:2] of the byte offset. More details ARM-ARM p. A4-11. 335 ResultPtr = ResultPtr - (intptr_t)RelocPos - 8; 336 ResultPtr = (ResultPtr & 0x03FFFFFC) >> 2; 337 assert(ResultPtr >= -33554432 && ResultPtr <= 33554428); 338 *((intptr_t*)RelocPos) |= ResultPtr; 339 break; 340 } 341 case ARM::reloc_arm_jt_base: { 342 // JT base - (instruction addr + 8) 343 ResultPtr = ResultPtr - (intptr_t)RelocPos - 8; 344 *((intptr_t*)RelocPos) |= ResultPtr; 345 break; 346 } 347 case ARM::reloc_arm_movw: { 348 ResultPtr = ResultPtr & 0xFFFF; 349 *((intptr_t*)RelocPos) |= ResultPtr & 0xFFF; 350 *((intptr_t*)RelocPos) |= ((ResultPtr >> 12) & 0xF) << 16; 351 break; 352 } 353 case ARM::reloc_arm_movt: { 354 ResultPtr = (ResultPtr >> 16) & 0xFFFF; 355 *((intptr_t*)RelocPos) |= ResultPtr & 0xFFF; 356 *((intptr_t*)RelocPos) |= ((ResultPtr >> 12) & 0xF) << 16; 357 break; 358 } 359 } 360 } 361 } 362