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https://github.com/c64scene-ar/llvm-6502.git
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c64bdf6aa5
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@58006 91177308-0d34-0410-b5e6-96231b3b80d8
213 lines
8.3 KiB
C++
213 lines
8.3 KiB
C++
//===-- ARMJITInfo.cpp - Implement the JIT interfaces for the ARM target --===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the JIT interfaces for the ARM target.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "jit"
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#include "ARMJITInfo.h"
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#include "ARMRelocations.h"
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#include "ARMSubtarget.h"
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#include "llvm/Function.h"
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#include "llvm/CodeGen/MachineCodeEmitter.h"
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#include "llvm/Config/alloca.h"
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#include "llvm/Support/Streams.h"
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#include "llvm/System/Memory.h"
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#include <cstdlib>
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using namespace llvm;
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void ARMJITInfo::replaceMachineCodeForFunction(void *Old, void *New) {
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abort();
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}
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/// JITCompilerFunction - This contains the address of the JIT function used to
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/// compile a function lazily.
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static TargetJITInfo::JITCompilerFn JITCompilerFunction;
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// Get the ASMPREFIX for the current host. This is often '_'.
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#ifndef __USER_LABEL_PREFIX__
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#define __USER_LABEL_PREFIX__
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#endif
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#define GETASMPREFIX2(X) #X
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#define GETASMPREFIX(X) GETASMPREFIX2(X)
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#define ASMPREFIX GETASMPREFIX(__USER_LABEL_PREFIX__)
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// CompilationCallback stub - We can't use a C function with inline assembly in
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// it, because we the prolog/epilog inserted by GCC won't work for us (we need
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// to preserve more context and manipulate the stack directly). Instead,
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// write our own wrapper, which does things our way, so we have complete
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// control over register saving and restoring.
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extern "C" {
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#if defined(__arm__)
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void ARMCompilationCallback(void);
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asm(
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".text\n"
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".align 2\n"
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".globl " ASMPREFIX "ARMCompilationCallback\n"
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ASMPREFIX "ARMCompilationCallback:\n"
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// Save caller saved registers since they may contain stuff
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// for the real target function right now. We have to act as if this
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// whole compilation callback doesn't exist as far as the caller is
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// concerned, so we can't just preserve the callee saved regs.
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"stmdb sp!, {r0, r1, r2, r3, lr}\n"
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// The LR contains the address of the stub function on entry.
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// pass it as the argument to the C part of the callback
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"mov r0, lr\n"
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"sub sp, sp, #4\n"
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// Call the C portion of the callback
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"bl " ASMPREFIX "ARMCompilationCallbackC\n"
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"add sp, sp, #4\n"
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// Restoring the LR to the return address of the function that invoked
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// the stub and de-allocating the stack space for it requires us to
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// swap the two saved LR values on the stack, as they're backwards
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// for what we need since the pop instruction has a pre-determined
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// order for the registers.
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// +--------+
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// 0 | LR | Original return address
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// +--------+
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// 1 | LR | Stub address (start of stub)
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// 2-5 | R3..R0 | Saved registers (we need to preserve all regs)
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// +--------+
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//
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// We need to exchange the values in slots 0 and 1 so we can
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// return to the address in slot 1 with the address in slot 0
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// restored to the LR.
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"ldr r0, [sp,#20]\n"
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"ldr r1, [sp,#16]\n"
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"str r1, [sp,#20]\n"
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"str r0, [sp,#16]\n"
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// Return to the (newly modified) stub to invoke the real function.
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// The above twiddling of the saved return addresses allows us to
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// deallocate everything, including the LR the stub saved, all in one
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// pop instruction.
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"ldmia sp!, {r0, r1, r2, r3, lr, pc}\n"
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);
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#else // Not an ARM host
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void ARMCompilationCallback() {
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assert(0 && "Cannot call ARMCompilationCallback() on a non-ARM arch!\n");
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abort();
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}
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#endif
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}
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/// ARMCompilationCallbackC - This is the target-specific function invoked
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/// by the function stub when we did not know the real target of a call.
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/// This function must locate the start of the stub or call site and pass
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/// it into the JIT compiler function.
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extern "C" void ARMCompilationCallbackC(intptr_t StubAddr) {
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// Get the address of the compiled code for this function.
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intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)StubAddr);
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// Rewrite the call target... so that we don't end up here every time we
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// execute the call. We're replacing the first two instructions of the
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// stub with:
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// ldr pc, [pc,#-4]
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// <addr>
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bool ok = sys::Memory::setRangeWritable ((void*)StubAddr, 8);
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if (!ok)
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{
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cerr << "ERROR: Unable to mark stub writable\n";
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abort();
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}
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*(intptr_t *)StubAddr = 0xe51ff004;
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*(intptr_t *)(StubAddr+4) = NewVal;
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ok = sys::Memory::setRangeExecutable ((void*)StubAddr, 8);
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if (!ok)
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{
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cerr << "ERROR: Unable to mark stub executable\n";
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abort();
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}
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}
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TargetJITInfo::LazyResolverFn
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ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) {
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JITCompilerFunction = F;
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return ARMCompilationCallback;
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}
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void *ARMJITInfo::emitFunctionStub(const Function* F, void *Fn,
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MachineCodeEmitter &MCE) {
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unsigned addr = (intptr_t)Fn;
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// If this is just a call to an external function, emit a branch instead of a
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// call. The code is the same except for one bit of the last instruction.
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if (Fn != (void*)(intptr_t)ARMCompilationCallback) {
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// branch to the corresponding function addr
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// the stub is 8-byte size and 4-aligned
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MCE.startFunctionStub(F, 8, 4);
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MCE.emitWordLE(0xe51ff004); // LDR PC, [PC,#-4]
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MCE.emitWordLE(addr); // addr of function
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} else {
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// The compilation callback will overwrite the first two words of this
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// stub with indirect branch instructions targeting the compiled code.
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// This stub sets the return address to restart the stub, so that
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// the new branch will be invoked when we come back.
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//
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// branch and link to the compilation callback.
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// the stub is 16-byte size and 4-byte aligned.
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MCE.startFunctionStub(F, 16, 4);
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// Save LR so the callback can determine which stub called it.
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// The compilation callback is responsible for popping this prior
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// to returning.
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MCE.emitWordLE(0xe92d4000); // PUSH {lr}
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// Set the return address to go back to the start of this stub
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MCE.emitWordLE(0xe24fe00c); // SUB LR, PC, #12
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// Invoke the compilation callback
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MCE.emitWordLE(0xe51ff004); // LDR PC, [PC,#-4]
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// The address of the compilation callback
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MCE.emitWordLE((intptr_t)ARMCompilationCallback);
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}
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return MCE.finishFunctionStub(F);
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}
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/// relocate - Before the JIT can run a block of code that has been emitted,
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/// it must rewrite the code to contain the actual addresses of any
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/// referenced global symbols.
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void ARMJITInfo::relocate(void *Function, MachineRelocation *MR,
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unsigned NumRelocs, unsigned char* GOTBase) {
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for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
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void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
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intptr_t ResultPtr = (intptr_t)MR->getResultPointer();
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switch ((ARM::RelocationType)MR->getRelocationType()) {
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case ARM::reloc_arm_relative: {
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// It is necessary to calculate the correct PC relative value. We
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// subtract the base addr from the target addr to form a byte offset.
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ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
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// If the result is positive, set bit U(23) to 1.
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if (ResultPtr >= 0)
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*((unsigned*)RelocPos) |= 1 << 23;
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else {
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// otherwise, obtain the absolute value and set
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// bit U(23) to 0.
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ResultPtr *= -1;
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*((unsigned*)RelocPos) &= 0xFF7FFFFF;
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}
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// set the immed value calculated
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*((unsigned*)RelocPos) |= (unsigned)ResultPtr;
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// set register Rn to PC
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*((unsigned*)RelocPos) |= 0xF << 16;
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break;
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}
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case ARM::reloc_arm_branch: {
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// It is necessary to calculate the correct value of signed_immed_24
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// field. We subtract the base addr from the target addr to form a
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// byte offset, which must be inside the range -33554432 and +33554428.
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// Then, we set the signed_immed_24 field of the instruction to bits
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// [25:2] of the byte offset. More details ARM-ARM p. A4-11.
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ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
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ResultPtr = (ResultPtr & 0x03FFFFFC) >> 2;
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assert(ResultPtr >= -33554432 && ResultPtr <= 33554428);
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*((unsigned*)RelocPos) |= ResultPtr;
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break;
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}
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}
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}
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}
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