diff options
| -rw-r--r-- | llvm/lib/Target/ARM/ARMJITInfo.cpp | 73 |
1 files changed, 43 insertions, 30 deletions
diff --git a/llvm/lib/Target/ARM/ARMJITInfo.cpp b/llvm/lib/Target/ARM/ARMJITInfo.cpp index 9622a29272c..945f014155d 100644 --- a/llvm/lib/Target/ARM/ARMJITInfo.cpp +++ b/llvm/lib/Target/ARM/ARMJITInfo.cpp @@ -21,12 +21,7 @@ using namespace llvm; void ARMJITInfo::replaceMachineCodeForFunction(void *Old, void *New) { - unsigned char *OldByte = (unsigned char *)Old; - *OldByte++ = 0xEA; // Emit B opcode. - unsigned *OldWord = (unsigned *)OldByte; - unsigned NewAddr = (intptr_t)New; - unsigned OldAddr = (intptr_t)OldWord; - *OldWord = NewAddr - OldAddr - 4; // Emit PC-relative addr of New code. + abort(); } /// JITCompilerFunction - This contains the address of the JIT function used to @@ -80,18 +75,16 @@ extern "C" void ARMCompilationCallbackC(intptr_t *StackPtr, intptr_t RetAddr) { << ": Resolving call to function: " << TheVM->getFunctionReferencedName((void*)RetAddr) << "\n"; #endif + intptr_t Addr = RetAddr - 4; - // Sanity check to make sure this really is a branch and link instruction. - assert(((unsigned char*)RetAddr-1)[3] == 0xEB && "Not a branch and link instr!"); - - intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)RetAddr); + intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)Addr); // Rewrite the call target... so that we don't end up here every time we // execute the call. - *(intptr_t *)RetAddr = (intptr_t)(NewVal-RetAddr-4); + *(intptr_t *)Addr = NewVal; // Change the return address to reexecute the branch and link instruction... - *RetAddrLoc -= 1; + *RetAddrLoc -= 12; } TargetJITInfo::LazyResolverFn @@ -101,23 +94,25 @@ ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) { } void *ARMJITInfo::emitFunctionStub(void *Fn, MachineCodeEmitter &MCE) { - unsigned addr = (intptr_t)Fn-MCE.getCurrentPCValue()-4; + unsigned addr = (intptr_t)Fn; // 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) { - MCE.startFunctionStub(4, 2); - MCE.emitByte(0xEA); // branch to the corresponding function addr - MCE.emitByte((unsigned char)(addr >> 0)); - MCE.emitByte((unsigned char)(addr >> 8)); - MCE.emitByte((unsigned char)(addr >> 16)); - return MCE.finishFunctionStub(0); + // branch to the corresponding function addr + // the stub is 8-byte size and 4-aligned + MCE.startFunctionStub(8, 4); + MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4] + MCE.emitWordLE(addr); // addr of function } else { - MCE.startFunctionStub(5, 2); - MCE.emitByte(0xEB); // branch and link to the corresponding function addr + // branch and link to the corresponding function addr + // the stub is 20-byte size and 4-aligned + MCE.startFunctionStub(20, 4); + MCE.emitWordLE(0xE92D4800); // STMFD SP!, [R11, LR] + MCE.emitWordLE(0xE28FE004); // ADD LR, PC, #4 + MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4] + MCE.emitWordLE(addr); // addr of function + MCE.emitWordLE(0xE8BD8800); // LDMFD SP!, [R11, PC] } - MCE.emitByte((unsigned char)(addr >> 0)); - MCE.emitByte((unsigned char)(addr >> 8)); - MCE.emitByte((unsigned char)(addr >> 16)); return MCE.finishFunctionStub(0); } @@ -132,15 +127,33 @@ void ARMJITInfo::relocate(void *Function, MachineRelocation *MR, intptr_t ResultPtr = (intptr_t)MR->getResultPointer(); switch ((ARM::RelocationType)MR->getRelocationType()) { case ARM::reloc_arm_relative: { - // PC relative relocation - *((unsigned*)RelocPos) += (unsigned)ResultPtr; + // 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) + *((unsigned*)RelocPos) |= 1 << 23; + else { + // otherwise, obtain the absolute value and set + // bit U(23) to 0. + ResultPtr *= -1; + *((unsigned*)RelocPos) &= 0xFF7FFFFF; + } + // set the immed value calculated + *((unsigned*)RelocPos) |= (unsigned)ResultPtr; + // set register Rn to PC + *((unsigned*)RelocPos) |= 0xF << 16; break; } - case ARM::reloc_arm_absolute: - break; case ARM::reloc_arm_branch: { - // relocation to b and bl instructions - ResultPtr = (ResultPtr-(intptr_t)RelocPos) >> 2; + // 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); *((unsigned*)RelocPos) |= ResultPtr; break; } |
