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LCC编译器的源程序分析(54)指令模式匹配

编译器分析指令 54 模式匹配源程序 LCC

2023-09-14 09:10:39 时间

在 LCC 编译器里，先把下面的语句翻译成中间表示，

int nTest1 = 1;

其中间表示的树如下：

ASGNI4(ADDRLP4(nTest1), CNSTI4(1))

然后根据上述的中间表示进行指令模式匹配。

下面的函数 _label 就是进行这样的工作：

#001 static void _label(NODEPTR_TYPE a) {

#002 int c;

#003 struct _state *p;

#004

#005 if (!a)

#006 fatal("_label", "Null tree/n", 0);

#007 STATE_LABEL(a) = p = allocate(sizeof *p, FUNC);

#008 p->rule._stmt = 0;

#009 ...

#010 switch (OP_LABEL(a)) {

#011 case 41: /* ARGB */

#012

#013 ...

#014 case 4149: /* ASGNI4 */

#015 _label(LEFT_CHILD(a));

#016 _label(RIGHT_CHILD(a));

#017 if ( /* stmt: ASGNI4(VREGP,reg) */

#018 LEFT_CHILD(a)->op == 711 /* VREGP */

#019 ) {

#020 c = ((struct _state *)(RIGHT_CHILD(a)->x.state))->cost[_reg_NT] + 0;

#021 if (c + 0 < p->cost[_stmt_NT]) {

#022 p->cost[_stmt_NT] = c + 0;

#023 p->rule._stmt = 6;

#024 }

#025 }

#026 if ( /* stmt: ASGNI4(addr,ADDI4(mem,con1)) */

#027 RIGHT_CHILD(a)->op == 4405 /* ADDI4 */

#028 ) {

#029 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#030 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con1_NT] + (memop(a));

#031 if (c + 0 < p->cost[_stmt_NT]) {

#032 p->cost[_stmt_NT] = c + 0;

#033 p->rule._stmt = 14;

#034 }

#035 }

#036 if ( /* stmt: ASGNI4(addr,ADDU4(mem,con1)) */

#037 RIGHT_CHILD(a)->op == 4406 /* ADDU4 */

#038 ) {

#039 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#040 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con1_NT] + (memop(a));

#041 if (c + 0 < p->cost[_stmt_NT]) {

#042 p->cost[_stmt_NT] = c + 0;

#043 p->rule._stmt = 15;

#044 }

#045 }

#046 if ( /* stmt: ASGNI4(addr,SUBI4(mem,con1)) */

#047 RIGHT_CHILD(a)->op == 4421 /* SUBI4 */

#048 ) {

#049 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#050 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con1_NT] + (memop(a));

#051 if (c + 0 < p->cost[_stmt_NT]) {

#052 p->cost[_stmt_NT] = c + 0;

#053 p->rule._stmt = 17;

#054 }

#055 }

#056 if ( /* stmt: ASGNI4(addr,SUBU4(mem,con1)) */

#057 RIGHT_CHILD(a)->op == 4422 /* SUBU4 */

#058 ) {

#059 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#060 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con1_NT] + (memop(a));

#061 if (c + 0 < p->cost[_stmt_NT]) {

#062 p->cost[_stmt_NT] = c + 0;

#063 p->rule._stmt = 18;

#064 }

#065 }

#066 if ( /* stmt: ASGNI4(addr,ADDI4(mem,rc)) */

#067 RIGHT_CHILD(a)->op == 4405 /* ADDI4 */

#068 ) {

#069 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#070 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_rc_NT] + (memop(a));

#071 if (c + 0 < p->cost[_stmt_NT]) {

#072 p->cost[_stmt_NT] = c + 0;

#073 p->rule._stmt = 20;

#074 }

#075 }

#076 if ( /* stmt: ASGNI4(addr,SUBI4(mem,rc)) */

#077 RIGHT_CHILD(a)->op == 4421 /* SUBI4 */

#078 ) {

#079 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#080 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_rc_NT] + (memop(a));

#081 if (c + 0 < p->cost[_stmt_NT]) {

#082 p->cost[_stmt_NT] = c + 0;

#083 p->rule._stmt = 21;

#084 }

#085 }

#086 if ( /* stmt: ASGNI4(addr,BANDI4(mem,rc)) */

#087 RIGHT_CHILD(a)->op == 4485 /* BANDI4 */

#088 ) {

#089 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#090 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_rc_NT] + (memop(a));

#091 if (c + 0 < p->cost[_stmt_NT]) {

#092 p->cost[_stmt_NT] = c + 0;

#093 p->rule._stmt = 24;

#094 }

#095 }

#096 if ( /* stmt: ASGNI4(addr,BORI4(mem,rc)) */

#097 RIGHT_CHILD(a)->op == 4517 /* BORI4 */

#098 ) {

#099 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#100 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_rc_NT] + (memop(a));

#101 if (c + 0 < p->cost[_stmt_NT]) {

#102 p->cost[_stmt_NT] = c + 0;

#103 p->rule._stmt = 25;

#104 }

#105 }

#106 if ( /* stmt: ASGNI4(addr,BXORI4(mem,rc)) */

#107 RIGHT_CHILD(a)->op == 4533 /* BXORI4 */

#108 ) {

#109 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#110 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_rc_NT] + (memop(a));

#111 if (c + 0 < p->cost[_stmt_NT]) {

#112 p->cost[_stmt_NT] = c + 0;

#113 p->rule._stmt = 26;

#114 }

#115 }

#116 if ( /* stmt: ASGNI4(addr,BCOMI4(mem)) */

#117 RIGHT_CHILD(a)->op == 4501 /* BCOMI4 */

#118 ) {

#119 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#120 [_mem_NT] + (memop(a));

#121 if (c + 0 < p->cost[_stmt_NT]) {

#122 p->cost[_stmt_NT] = c + 0;

#123 p->rule._stmt = 30;

#124 }

#125 }

#126 if ( /* stmt: ASGNI4(addr,NEGI4(mem)) */

#127 RIGHT_CHILD(a)->op == 4293 /* NEGI4 */

#128 ) {

#129 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#130 [_mem_NT] + (memop(a));

#131 if (c + 0 < p->cost[_stmt_NT]) {

#132 p->cost[_stmt_NT] = c + 0;

#133 p->rule._stmt = 32;

#134 }

#135 }

#136 if ( /* stmt: ASGNI4(addr,LSHI4(mem,con5)) */

#137 RIGHT_CHILD(a)->op == 4437 /* LSHI4 */

#138 ) {

#139 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#140 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con5_NT] + (memop(a));

#141 if (c + 0 < p->cost[_stmt_NT]) {

#142 p->cost[_stmt_NT] = c + 0;

#143 p->rule._stmt = 33;

#144 }

#145 }

#146 if ( /* stmt: ASGNI4(addr,LSHU4(mem,con5)) */

#147 RIGHT_CHILD(a)->op == 4438 /* LSHU4 */

#148 ) {

#149 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#150 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con5_NT] + (memop(a));

#151 if (c + 0 < p->cost[_stmt_NT]) {

#152 p->cost[_stmt_NT] = c + 0;

#153 p->rule._stmt = 34;

#154 }

#155 }

#156 if ( /* stmt: ASGNI4(addr,RSHI4(mem,con5)) */

#157 RIGHT_CHILD(a)->op == 4469 /* RSHI4 */

#158 ) {

#159 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#160 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con5_NT] + (memop(a));

#161 if (c + 0 < p->cost[_stmt_NT]) {

#162 p->cost[_stmt_NT] = c + 0;

#163 p->rule._stmt = 35;

#164 }

#165 }

#166 if ( /* stmt: ASGNI4(addr,RSHU4(mem,con5)) */

#167 RIGHT_CHILD(a)->op == 4470 /* RSHU4 */

#168 ) {

#169 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(LEFT_CHILD(RIGHT_CHILD(a))->x.state))->cost

#170 [_mem_NT] + ((struct _state *)(RIGHT_CHILD(RIGHT_CHILD(a))->x.state))->cost[_con5_NT] + (memop(a));

#171 if (c + 0 < p->cost[_stmt_NT]) {

#172 p->cost[_stmt_NT] = c + 0;

#173 p->rule._stmt = 36;

#174 }

#175 }

#176 /* stmt: ASGNI4(addr,rc) */

#177 c = ((struct _state *)(LEFT_CHILD(a)->x.state))->cost[_addr_NT] + ((struct _state *)(RIGHT_CHILD(a)->x.state))->cost[_rc_NT] + 1;

#178 if (c + 0 < p->cost[_stmt_NT]) {

#179 p->cost[_stmt_NT] = c + 0;

#180 p->rule._stmt = 39;

#181 }

#182 break;

#183 ...

#184

第 7 行创建一个节点的状态空间。

第 10 行根据节点的类型选择不同的操作，也就是进行指令选择。

由分析中间表示树可知，第一个节点是 ASGNI4 ，所以就运行到第 14 行那里。

第 15 行进行左子树递归处理。

第 16 行进行右子树递归处理。

接着下来的程序就会根据左子树和右子树的类型，从下面的语句里选择出合适的指令，

stmt: ASGNI4(VREGP,reg)

stmt: ASGNI4(addr,ADDI4(mem,con1))

stmt: ASGNI4(addr,ADDU4(mem,con1))

stmt: ASGNI4(addr,SUBI4(mem,con1))

stmt: ASGNI4(addr,SUBU4(mem,con1))

stmt: ASGNI4(addr,ADDI4(mem,rc))

stmt: ASGNI4(addr,SUBI4(mem,rc))

stmt: ASGNI4(addr,BANDI4(mem,rc))

stmt: ASGNI4(addr,BORI4(mem,rc))

stmt: ASGNI4(addr,BXORI4(mem,rc))

stmt: ASGNI4(addr,BCOMI4(mem))

stmt: ASGNI4(addr,NEGI4(mem))

stmt: ASGNI4(addr,LSHI4(mem,con5))

stmt: ASGNI4(addr,LSHU4(mem,con5))

stmt: ASGNI4(addr,RSHI4(mem,con5))

stmt: ASGNI4(addr,RSHU4(mem,con5))

stmt: ASGNI4(addr,rc)

由于中间表示就可以知道从上面的指令里是选择最后一条指令生成，所以在第 179 行里设置了这条指令的开销，第 180 行里设置指令编码为 39 。

通过这样的计算，就可以选择出合适的指令。有了这两个值，后面会通过其它函数来生成上面的目标代码，下一次再解释怎么样生成目标代码。

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