1 //===-- ARMJITInfo.cpp - Implement the JIT interfaces for the ARM target --===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements the JIT interfaces for the ARM target.
12 //===----------------------------------------------------------------------===//
14 #define DEBUG_TYPE "jit"
15 #include "ARMJITInfo.h"
16 #include "ARMRelocations.h"
17 #include "ARMSubtarget.h"
18 #include "llvm/Function.h"
19 #include "llvm/CodeGen/MachineCodeEmitter.h"
20 #include "llvm/Config/alloca.h"
24 void ARMJITInfo::replaceMachineCodeForFunction(void *Old, void *New) {
28 /// JITCompilerFunction - This contains the address of the JIT function used to
29 /// compile a function lazily.
30 static TargetJITInfo::JITCompilerFn JITCompilerFunction;
32 // Get the ASMPREFIX for the current host. This is often '_'.
33 #ifndef __USER_LABEL_PREFIX__
34 #define __USER_LABEL_PREFIX__
36 #define GETASMPREFIX2(X) #X
37 #define GETASMPREFIX(X) GETASMPREFIX2(X)
38 #define ASMPREFIX GETASMPREFIX(__USER_LABEL_PREFIX__)
40 // CompilationCallback stub - We can't use a C function with inline assembly in
41 // it, because we the prolog/epilog inserted by GCC won't work for us. Instead,
42 // write our own wrapper, which does things our way, so we have complete control
43 // over register saving and restoring.
46 void ARMCompilationCallback(void);
50 ".globl " ASMPREFIX "ARMCompilationCallback\n"
51 ASMPREFIX "ARMCompilationCallback:\n"
52 // save main registers
53 #if defined(__APPLE__)
54 "stmfd sp!, {r4, r5, r6, r7, lr}\n"
55 "mov r0, r7\n" // stub's frame
56 "stmfd sp!, {r8, r10, r11}\n"
59 "stmfd sp!, {fp, ip, lr, pc}\n"
62 // arguments to Compilation Callback
63 // r0 - our lr (address of the call instruction in stub plus 4)
64 // r1 - stub's lr (address of instruction that called the stub plus 4)
65 #if defined(__APPLE__)
66 "mov r0, r7\n" // stub's frame
68 "mov r0, fp\n" // stub's frame
70 "mov r1, lr\n" // stub's lr
71 "bl " ASMPREFIX "ARMCompilationCallbackC\n"
72 // restore main registers
73 #if defined(__APPLE__)
74 "ldmfd sp!, {r8, r10, r11}\n"
75 "ldmfd sp!, {r4, r5, r6, r7, pc}\n"
77 "ldmfd sp, {fp, sp, pc}\n"
80 #else // Not an ARM host
81 void ARMCompilationCallback() {
82 assert(0 && "Cannot call ARMCompilationCallback() on a non-ARM arch!\n");
88 /// ARMCompilationCallbackC - This is the target-specific function invoked by the
89 /// function stub when we did not know the real target of a call. This function
90 /// must locate the start of the stub or call site and pass it into the JIT
91 /// compiler function.
92 extern "C" void ARMCompilationCallbackC(intptr_t *StackPtr, intptr_t RetAddr) {
93 intptr_t *RetAddrLoc = &StackPtr[-1];
95 assert(*RetAddrLoc == RetAddr &&
96 "Could not find return address on the stack!");
98 DOUT << "In callback! Addr=" << (void*)RetAddr
99 << " FP=" << (void*)StackPtr
100 << ": Resolving call to function: "
101 << TheVM->getFunctionReferencedName((void*)RetAddr) << "\n";
103 intptr_t Addr = RetAddr - 4;
105 intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)Addr);
107 // Rewrite the call target... so that we don't end up here every time we
109 *(intptr_t *)Addr = NewVal;
111 // Change the return address to reexecute the branch and link instruction...
115 TargetJITInfo::LazyResolverFn
116 ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) {
117 JITCompilerFunction = F;
118 return ARMCompilationCallback;
121 void *ARMJITInfo::emitFunctionStub(const Function* F, void *Fn,
122 MachineCodeEmitter &MCE) {
123 unsigned addr = (intptr_t)Fn;
124 // If this is just a call to an external function, emit a branch instead of a
125 // call. The code is the same except for one bit of the last instruction.
126 if (Fn != (void*)(intptr_t)ARMCompilationCallback) {
127 // branch to the corresponding function addr
128 // the stub is 8-byte size and 4-aligned
129 MCE.startFunctionStub(F, 8, 4);
130 MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4]
131 MCE.emitWordLE(addr); // addr of function
133 // branch and link to the corresponding function addr
134 // the stub is 20-byte size and 4-aligned
135 MCE.startFunctionStub(F, 20, 4);
136 MCE.emitWordLE(0xE92D4800); // STMFD SP!, [R11, LR]
137 MCE.emitWordLE(0xE28FE004); // ADD LR, PC, #4
138 MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4]
139 MCE.emitWordLE(addr); // addr of function
140 MCE.emitWordLE(0xE8BD8800); // LDMFD SP!, [R11, PC]
143 return MCE.finishFunctionStub(F);
146 /// relocate - Before the JIT can run a block of code that has been emitted,
147 /// it must rewrite the code to contain the actual addresses of any
148 /// referenced global symbols.
149 void ARMJITInfo::relocate(void *Function, MachineRelocation *MR,
150 unsigned NumRelocs, unsigned char* GOTBase) {
151 for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
152 void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
153 intptr_t ResultPtr = (intptr_t)MR->getResultPointer();
154 switch ((ARM::RelocationType)MR->getRelocationType()) {
155 case ARM::reloc_arm_relative: {
156 // It is necessary to calculate the correct PC relative value. We
157 // subtract the base addr from the target addr to form a byte offset.
158 ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
159 // If the result is positive, set bit U(23) to 1.
161 *((unsigned*)RelocPos) |= 1 << 23;
163 // otherwise, obtain the absolute value and set
166 *((unsigned*)RelocPos) &= 0xFF7FFFFF;
168 // set the immed value calculated
169 *((unsigned*)RelocPos) |= (unsigned)ResultPtr;
170 // set register Rn to PC
171 *((unsigned*)RelocPos) |= 0xF << 16;
174 case ARM::reloc_arm_branch: {
175 // It is necessary to calculate the correct value of signed_immed_24
176 // field. We subtract the base addr from the target addr to form a
177 // byte offset, which must be inside the range -33554432 and +33554428.
178 // Then, we set the signed_immed_24 field of the instruction to bits
179 // [25:2] of the byte offset. More details ARM-ARM p. A4-11.
180 ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
181 ResultPtr = (ResultPtr & 0x03FFFFFC) >> 2;
182 assert(ResultPtr >= -33554432 && ResultPtr <= 33554428);
183 *((unsigned*)RelocPos) |= ResultPtr;