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 // CompilationCallback stub - We can't use a C function with inline assembly in
33 // it, because we the prolog/epilog inserted by GCC won't work for us. Instead,
34 // write our own wrapper, which does things our way, so we have complete control
35 // over register saving and restoring.
38 void ARMCompilationCallback(void);
42 ".globl ARMCompilationCallback\n"
43 "ARMCompilationCallback:\n"
44 // save main registers
46 "stmfd sp!, {fp, ip, lr, pc}\n"
48 // arguments to Compilation Callback
49 // r0 - our lr (address of the call instruction in stub plus 4)
50 // r1 - stub's lr (address of instruction that called the stub plus 4)
51 "mov r0, fp\n" // stub's frame
52 "mov r1, lr\n" // stub's lr
53 "bl ARMCompilationCallbackC\n"
54 // restore main registers
55 "ldmfd sp, {fp, sp, pc}\n");
56 #else // Not an ARM host
57 void ARMCompilationCallback() {
58 assert(0 && "Cannot call ARMCompilationCallback() on a non-ARM arch!\n");
64 /// ARMCompilationCallbackC - This is the target-specific function invoked by the
65 /// function stub when we did not know the real target of a call. This function
66 /// must locate the start of the stub or call site and pass it into the JIT
67 /// compiler function.
68 extern "C" void ARMCompilationCallbackC(intptr_t *StackPtr, intptr_t RetAddr) {
69 intptr_t *RetAddrLoc = &StackPtr[-1];
71 assert(*RetAddrLoc == RetAddr &&
72 "Could not find return address on the stack!");
74 DOUT << "In callback! Addr=" << (void*)RetAddr
75 << " FP=" << (void*)StackPtr
76 << ": Resolving call to function: "
77 << TheVM->getFunctionReferencedName((void*)RetAddr) << "\n";
79 intptr_t Addr = RetAddr - 4;
81 intptr_t NewVal = (intptr_t)JITCompilerFunction((void*)Addr);
83 // Rewrite the call target... so that we don't end up here every time we
85 *(intptr_t *)Addr = NewVal;
87 // Change the return address to reexecute the branch and link instruction...
91 TargetJITInfo::LazyResolverFn
92 ARMJITInfo::getLazyResolverFunction(JITCompilerFn F) {
93 JITCompilerFunction = F;
94 return ARMCompilationCallback;
97 void *ARMJITInfo::emitFunctionStub(const Function* F, void *Fn,
98 MachineCodeEmitter &MCE) {
99 unsigned addr = (intptr_t)Fn;
100 // If this is just a call to an external function, emit a branch instead of a
101 // call. The code is the same except for one bit of the last instruction.
102 if (Fn != (void*)(intptr_t)ARMCompilationCallback) {
103 // branch to the corresponding function addr
104 // the stub is 8-byte size and 4-aligned
105 MCE.startFunctionStub(F, 8, 4);
106 MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4]
107 MCE.emitWordLE(addr); // addr of function
109 // branch and link to the corresponding function addr
110 // the stub is 20-byte size and 4-aligned
111 MCE.startFunctionStub(F, 20, 4);
112 MCE.emitWordLE(0xE92D4800); // STMFD SP!, [R11, LR]
113 MCE.emitWordLE(0xE28FE004); // ADD LR, PC, #4
114 MCE.emitWordLE(0xE51FF004); // LDR PC, [PC,#-4]
115 MCE.emitWordLE(addr); // addr of function
116 MCE.emitWordLE(0xE8BD8800); // LDMFD SP!, [R11, PC]
119 return MCE.finishFunctionStub(F);
122 /// relocate - Before the JIT can run a block of code that has been emitted,
123 /// it must rewrite the code to contain the actual addresses of any
124 /// referenced global symbols.
125 void ARMJITInfo::relocate(void *Function, MachineRelocation *MR,
126 unsigned NumRelocs, unsigned char* GOTBase) {
127 for (unsigned i = 0; i != NumRelocs; ++i, ++MR) {
128 void *RelocPos = (char*)Function + MR->getMachineCodeOffset();
129 intptr_t ResultPtr = (intptr_t)MR->getResultPointer();
130 switch ((ARM::RelocationType)MR->getRelocationType()) {
131 case ARM::reloc_arm_relative: {
132 // It is necessary to calculate the correct PC relative value. We
133 // subtract the base addr from the target addr to form a byte offset.
134 ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
135 // If the result is positive, set bit U(23) to 1.
137 *((unsigned*)RelocPos) |= 1 << 23;
139 // otherwise, obtain the absolute value and set
142 *((unsigned*)RelocPos) &= 0xFF7FFFFF;
144 // set the immed value calculated
145 *((unsigned*)RelocPos) |= (unsigned)ResultPtr;
146 // set register Rn to PC
147 *((unsigned*)RelocPos) |= 0xF << 16;
150 case ARM::reloc_arm_branch: {
151 // It is necessary to calculate the correct value of signed_immed_24
152 // field. We subtract the base addr from the target addr to form a
153 // byte offset, which must be inside the range -33554432 and +33554428.
154 // Then, we set the signed_immed_24 field of the instruction to bits
155 // [25:2] of the byte offset. More details ARM-ARM p. A4-11.
156 ResultPtr = ResultPtr-(intptr_t)RelocPos-8;
157 ResultPtr = (ResultPtr & 0x03FFFFFC) >> 2;
158 assert(ResultPtr >= -33554432 && ResultPtr <= 33554428);
159 *((unsigned*)RelocPos) |= ResultPtr;