1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
|
/*
* tclOptimize.c --
*
* This file contains the bytecode optimizer.
*
* Copyright (c) 2013 by Donal Fellows.
*
* See the file "license.terms" for information on usage and redistribution of
* this file, and for a DISCLAIMER OF ALL WARRANTIES.
*/
#include "tclInt.h"
#include "tclCompile.h"
#include <assert.h>
#define DefineTargetAddress(tablePtr, address) \
((void) Tcl_CreateHashEntry((tablePtr), (void *) (address), &isNew))
#define IsTargetAddress(tablePtr, address) \
(Tcl_FindHashEntry((tablePtr), (void *) (address)) != NULL)
static void
LocateTargetAddresses(
CompileEnv *envPtr,
Tcl_HashTable *tablePtr)
{
unsigned char *pc, *target;
int size, isNew, i;
Tcl_HashEntry *hPtr;
Tcl_HashSearch hSearch;
Tcl_InitHashTable(tablePtr, TCL_ONE_WORD_KEYS);
/*
* The starts of commands represent target addresses.
*/
for (i=0 ; i<envPtr->numCommands ; i++) {
DefineTargetAddress(tablePtr,
envPtr->codeStart + envPtr->cmdMapPtr[i].codeOffset);
}
/*
* Find places where we should be careful about replacing instructions
* because they are the targets of various types of jumps.
*/
for (pc = envPtr->codeStart ; pc < envPtr->codeNext ; pc += size) {
size = tclInstructionTable[*pc].numBytes;
switch (*pc) {
case INST_JUMP1:
case INST_JUMP_TRUE1:
case INST_JUMP_FALSE1:
target = pc + TclGetInt1AtPtr(pc+1);
goto storeTarget;
case INST_JUMP4:
case INST_JUMP_TRUE4:
case INST_JUMP_FALSE4:
target = pc + TclGetInt4AtPtr(pc+1);
goto storeTarget;
case INST_BEGIN_CATCH4:
target = envPtr->codeStart + envPtr->exceptArrayPtr[
TclGetUInt4AtPtr(pc+1)].codeOffset;
storeTarget:
DefineTargetAddress(tablePtr, target);
break;
case INST_JUMP_TABLE:
hPtr = Tcl_FirstHashEntry(
&JUMPTABLEINFO(envPtr, pc+1)->hashTable, &hSearch);
for (; hPtr ; hPtr = Tcl_NextHashEntry(&hSearch)) {
target = pc + PTR2INT(Tcl_GetHashValue(hPtr));
DefineTargetAddress(tablePtr, target);
}
break;
case INST_RETURN_CODE_BRANCH:
for (i=TCL_ERROR ; i<TCL_CONTINUE+1 ; i++) {
DefineTargetAddress(tablePtr, pc + 2*i - 1);
}
break;
case INST_START_CMD:
assert (envPtr->atCmdStart < 2);
}
}
/*
* Add a marker *after* the last bytecode instruction. WARNING: points to
* one past the end!
*/
DefineTargetAddress(tablePtr, pc);
/*
* Enter in the targets of exception ranges.
*/
for (i=0 ; i<envPtr->exceptArrayNext ; i++) {
ExceptionRange *rangePtr = &envPtr->exceptArrayPtr[i];
if (rangePtr->type == CATCH_EXCEPTION_RANGE) {
target = envPtr->codeStart + rangePtr->catchOffset;
DefineTargetAddress(tablePtr, target);
} else {
target = envPtr->codeStart + rangePtr->breakOffset;
DefineTargetAddress(tablePtr, target);
if (rangePtr->continueOffset >= 0) {
target = envPtr->codeStart + rangePtr->continueOffset;
DefineTargetAddress(tablePtr, target);
}
}
}
}
/*
* ----------------------------------------------------------------------
*
* TclOptimizeBytecode --
*
* A very simple peephole optimizer for bytecode.
*
* ----------------------------------------------------------------------
*/
void
TclOptimizeBytecode(
CompileEnv *envPtr)
{
unsigned char *pc;
int size;
Tcl_HashTable targets;
/*
* Replace PUSH/POP sequences (when non-hazardous) with NOPs. Also replace
* PUSH empty/CONCAT and TRY_CVT_NUMERIC (when followed by an operation
* that guarantees the check for arithmeticity) and eliminate LNOT when we
* can invert the following JUMP condition.
*/
LocateTargetAddresses(envPtr, &targets);
for (pc = envPtr->codeStart ; pc < envPtr->codeNext ; pc += size) {
int blank = 0, i, inst;
size = tclInstructionTable[*pc].numBytes;
while (*(pc+size) == INST_NOP) {
if (IsTargetAddress(&targets, pc + size)) {
break;
}
size += tclInstructionTable[INST_NOP].numBytes;
}
if (IsTargetAddress(&targets, pc + size)) {
continue;
}
inst = *(pc + size);
switch (*pc) {
case INST_PUSH1:
if (inst == INST_POP) {
blank = size + tclInstructionTable[inst].numBytes;
} else if (inst == INST_CONCAT1
&& TclGetUInt1AtPtr(pc + size + 1) == 2) {
Tcl_Obj *litPtr = TclFetchLiteral(envPtr,
TclGetUInt1AtPtr(pc + 1));
int numBytes;
(void) Tcl_GetStringFromObj(litPtr, &numBytes);
if (numBytes == 0) {
blank = size + tclInstructionTable[inst].numBytes;
}
}
break;
case INST_PUSH4:
if (inst == INST_POP) {
blank = size + 1;
} else if (inst == INST_CONCAT1
&& TclGetUInt1AtPtr(pc + size + 1) == 2) {
Tcl_Obj *litPtr = TclFetchLiteral(envPtr,
TclGetUInt4AtPtr(pc + 1));
int numBytes;
(void) Tcl_GetStringFromObj(litPtr, &numBytes);
if (numBytes == 0) {
blank = size + tclInstructionTable[inst].numBytes;
}
}
break;
case INST_LNOT:
switch (inst) {
case INST_JUMP_TRUE1:
blank = size;
*(pc + size) = INST_JUMP_FALSE1;
break;
case INST_JUMP_FALSE1:
blank = size;
*(pc + size) = INST_JUMP_TRUE1;
break;
case INST_JUMP_TRUE4:
blank = size;
*(pc + size) = INST_JUMP_FALSE4;
break;
case INST_JUMP_FALSE4:
blank = size;
*(pc + size) = INST_JUMP_TRUE4;
break;
}
break;
case INST_TRY_CVT_TO_NUMERIC:
switch (inst) {
case INST_JUMP_TRUE1:
case INST_JUMP_TRUE4:
case INST_JUMP_FALSE1:
case INST_JUMP_FALSE4:
case INST_INCR_SCALAR1:
case INST_INCR_ARRAY1:
case INST_INCR_ARRAY_STK:
case INST_INCR_SCALAR_STK:
case INST_INCR_STK:
case INST_LOR:
case INST_LAND:
case INST_EQ:
case INST_NEQ:
case INST_LT:
case INST_LE:
case INST_GT:
case INST_GE:
case INST_MOD:
case INST_LSHIFT:
case INST_RSHIFT:
case INST_BITOR:
case INST_BITXOR:
case INST_BITAND:
case INST_EXPON:
case INST_ADD:
case INST_SUB:
case INST_DIV:
case INST_MULT:
case INST_LNOT:
case INST_BITNOT:
case INST_UMINUS:
case INST_UPLUS:
case INST_TRY_CVT_TO_NUMERIC:
blank = size;
break;
}
break;
}
if (blank > 0) {
for (i=0 ; i<blank ; i++) {
*(pc + i) = INST_NOP;
}
size = blank;
}
}
Tcl_DeleteHashTable(&targets);
/*
* Trim unreachable instructions after a DONE.
*/
LocateTargetAddresses(envPtr, &targets);
for (pc = envPtr->codeStart ; pc < envPtr->codeNext-1 ; pc += size) {
int clear = 0;
size = tclInstructionTable[*pc].numBytes;
if (*pc != INST_DONE) {
continue;
}
assert (size == 1);
while (!IsTargetAddress(&targets, pc + 1 + clear)) {
clear += tclInstructionTable[*(pc + 1 + clear)].numBytes;
}
if (pc + 1 + clear == envPtr->codeNext) {
envPtr->codeNext -= clear;
} else {
while (clear --> 0) {
*(pc + 1 + clear) = INST_NOP;
}
}
}
Tcl_DeleteHashTable(&targets);
}
/*
* Local Variables:
* mode: c
* c-basic-offset: 4
* fill-column: 78
* tab-width: 8
* End:
*/
|
