1 /* 2 * Copyright (c) 2016 Thomas Pornin <pornin@bolet.org> 3 * 4 * Permission is hereby granted, free of charge, to any person obtaining 5 * a copy of this software and associated documentation files (the 6 * "Software"), to deal in the Software without restriction, including 7 * without limitation the rights to use, copy, modify, merge, publish, 8 * distribute, sublicense, and/or sell copies of the Software, and to 9 * permit persons to whom the Software is furnished to do so, subject to 10 * the following conditions: 11 * 12 * The above copyright notice and this permission notice shall be 13 * included in all copies or substantial portions of the Software. 14 * 15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, 16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF 17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND 18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS 19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN 20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN 21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE 22 * SOFTWARE. 23 */ 24 25 using System; 26 using System.Collections.Generic; 27 28 /* 29 * Execution of code during compilation is done in a virtual CPU 30 * incarnated by this class, that contains the relevant registers. 31 * 32 * Accesses to the data on the stack are mapped to accesses to an 33 * internal array, with no explicit control on boundaries. Since the 34 * internal array may be larger than the actual stack contents, 35 * nonsensical accesses may still "work" to some extent. The whole 36 * thing won't derail beyond the CLR VM, though. 37 */ 38 39 class CPU { 40 41 /* 42 * Next instruction to execute is in ipBuf[ipOff]. 43 */ 44 internal Opcode[] ipBuf; 45 internal int ipOff; 46 47 /* 48 * stackBuf and stackPtr implement the data stack. The system 49 * stack uses frames; 'rsp' points to the current top frame. 50 */ 51 TValue[] stackBuf; 52 int stackPtr; 53 Frame rsp; 54 CPU()55 internal CPU() 56 { 57 stackBuf = new TValue[16]; 58 stackPtr = -1; 59 rsp = null; 60 } 61 62 /* 63 * Enter a function, reserving space for 'numLocals' local variables. 64 */ Enter(Opcode[] code, int numLocals)65 internal void Enter(Opcode[] code, int numLocals) 66 { 67 Frame f = new Frame(rsp, numLocals); 68 rsp = f; 69 f.savedIpBuf = ipBuf; 70 f.savedIpOff = ipOff; 71 ipBuf = code; 72 ipOff = 0; 73 } 74 75 /* 76 * Exit the current function. 77 */ Exit()78 internal void Exit() 79 { 80 ipBuf = rsp.savedIpBuf; 81 ipOff = rsp.savedIpOff; 82 rsp = rsp.upper; 83 } 84 85 /* 86 * Get the current stack depth (number of elements). 87 */ 88 internal int Depth { 89 get { 90 return stackPtr + 1; 91 } 92 } 93 94 /* 95 * Pop a value from the stack. 96 */ Pop()97 internal TValue Pop() 98 { 99 return stackBuf[stackPtr --]; 100 } 101 102 /* 103 * Push a value on the stack. 104 */ Push(TValue v)105 internal void Push(TValue v) 106 { 107 int len = stackBuf.Length; 108 if (++ stackPtr == len) { 109 TValue[] nbuf = new TValue[len << 1]; 110 Array.Copy(stackBuf, 0, nbuf, 0, len); 111 stackBuf = nbuf; 112 } 113 stackBuf[stackPtr] = v; 114 } 115 116 /* 117 * Look at the value at depth 'depth' (0 is top of stack). The 118 * stack is unchanged. 119 */ Peek(int depth)120 internal TValue Peek(int depth) 121 { 122 return stackBuf[stackPtr - depth]; 123 } 124 125 /* 126 * Rotate the stack at depth 'depth': the value at that depth 127 * is moved to the top of stack. 128 */ Rot(int depth)129 internal void Rot(int depth) 130 { 131 TValue v = stackBuf[stackPtr - depth]; 132 Array.Copy(stackBuf, stackPtr - (depth - 1), 133 stackBuf, stackPtr - depth, depth); 134 stackBuf[stackPtr] = v; 135 } 136 137 /* 138 * Inverse-rotate the stack at depth 'depth': the value at the 139 * top of stack is moved to that depth. 140 */ NRot(int depth)141 internal void NRot(int depth) 142 { 143 TValue v = stackBuf[stackPtr]; 144 Array.Copy(stackBuf, stackPtr - depth, 145 stackBuf, stackPtr - (depth - 1), depth); 146 stackBuf[stackPtr - depth] = v; 147 } 148 149 /* 150 * Get the current contents of the local variable 'num'. 151 */ GetLocal(int num)152 internal TValue GetLocal(int num) 153 { 154 return rsp.locals[num]; 155 } 156 157 /* 158 * Set the contents of the local variable 'num'. 159 */ PutLocal(int num, TValue v)160 internal void PutLocal(int num, TValue v) 161 { 162 rsp.locals[num] = v; 163 } 164 165 /* 166 * The system stack really is a linked list of Frame instances. 167 */ 168 class Frame { 169 170 internal Frame upper; 171 internal Opcode[] savedIpBuf; 172 internal int savedIpOff; 173 internal TValue[] locals; 174 Frame(Frame upper, int numLocals)175 internal Frame(Frame upper, int numLocals) 176 { 177 this.upper = upper; 178 locals = new TValue[numLocals]; 179 } 180 } 181 } 182