mono/mini/abcremoval.h

   1 /*
   2  * abcremoval.h: Array bounds check removal
   3  *
   4  * Author:
   5  *   Massimiliano Mantione (massi@ximian.com)
   6  *
   7  * (C) 2004 Ximian, Inc.  http://www.ximian.com
   8  */
   9
  10 #ifndef __MONO_ABCREMOVAL_H__
  11 #define __MONO_ABCREMOVAL_H__
  12
  13 #include <limits.h>
  14
  15 #include "mini.h"
  16
  17
  18 /**
  19  * All handled value types (expressions) in variable definitions and branch
  20  * contitions:
  21  * ANY: not handled
  22  * CONSTANT: an integer constant
  23  * VARIABLE: a reference to a variable, with an optional delta (can be zero)
  24  * PHI: a PHI definition of the SSA representation
  25  */
  26 typedef enum {
  27         MONO_ANY_SUMMARIZED_VALUE,
  28         MONO_CONSTANT_SUMMARIZED_VALUE,
  29         MONO_VARIABLE_SUMMARIZED_VALUE,
  30         MONO_PHI_SUMMARIZED_VALUE
  31 } MonoSummarizedValueType;
  32
  33 /**
  34  * A MONO_CONSTANT_SUMMARIZED_VALUE value.
  35  * value: the value
  36  */
  37 typedef struct MonoSummarizedConstantValue {
  38         int value;
  39 } MonoSummarizedConstantValue;
  40
  41 /**
  42  * A MONO_VARIABLE_SUMMARIZED_VALUE value
  43  * variable: the variable index in the cfg
  44  * delta: the delta (can be zero)
  45  */
  46 typedef struct MonoSummarizedVariableValue {
  47         int variable;
  48         int delta;
  49 } MonoSummarizedVariableValue;
  50
  51 /**
  52  * A MONO_PHI_SUMMARIZED_VALUE value.
  53  * number_of_alternatives: the number of alternatives in the PHI definition
  54  * phi_alternatives: an array of integers with the indexes of the variables
  55  *                   which are the alternatives in this PHI definition
  56  */
  57 typedef struct MonoSummarizedPhiValue {
  58         int number_of_alternatives;
  59         int *phi_alternatives;
  60 } MonoSummarizedPhiValue;
  61
  62 /**
  63  * A summarized value.
  64  * In practice it is a "tagged union".
  65  */
  66 typedef struct MonoSummarizedValue {
  67         MonoSummarizedValueType type;
  68         union {
  69                 MonoSummarizedConstantValue constant;
  70                 MonoSummarizedVariableValue variable;
  71                 MonoSummarizedPhiValue phi;
  72         } value;
  73 } MonoSummarizedValue;
  74
  75 /**
  76  * A "relation" between two values.
  77  * The enumeration is used as a bit field, with three significant bits.
  78  * The degenerated cases are meaningful:
  79  * MONO_ANY_RELATION: we know nothing of this relation
  80  * MONO_NO_RELATION: no relation is possible (this code is unreachable)
  81  */
  82 typedef enum {
  83         MONO_EQ_RELATION = 1,
  84         MONO_LT_RELATION = 2,
  85         MONO_GT_RELATION = 4,
  86         MONO_NE_RELATION = (MONO_LT_RELATION|MONO_GT_RELATION),
  87         MONO_LE_RELATION = (MONO_LT_RELATION|MONO_EQ_RELATION),
  88         MONO_GE_RELATION = (MONO_GT_RELATION|MONO_EQ_RELATION),
  89         MONO_ANY_RELATION = (MONO_EQ_RELATION|MONO_LT_RELATION|MONO_GT_RELATION),
  90         MONO_NO_RELATION = 0
  91 } MonoValueRelation;
  92
  93 /**
  94  * A "kind" of integer value.
  95  * The enumeration is used as a bit field, with two fields.
  96  * The first, four bits wide, is the "sizeof" in bytes.
  97  * The second is a flag that is true if the value is unsigned.
  98  */
  99 typedef enum {
 100         MONO_INTEGER_VALUE_SIZE_1 = 1,
 101         MONO_INTEGER_VALUE_SIZE_2 = 2,
 102         MONO_INTEGER_VALUE_SIZE_4 = 4,
 103         MONO_INTEGER_VALUE_SIZE_8 = 8,
 104         MONO_INTEGER_VALUE_SIZE_BITMASK = 15,
 105         MONO_UNSIGNED_VALUE_FLAG = 16,
 106         MONO_UNSIGNED_INTEGER_VALUE_SIZE_1 = MONO_UNSIGNED_VALUE_FLAG|MONO_INTEGER_VALUE_SIZE_1,
 107         MONO_UNSIGNED_INTEGER_VALUE_SIZE_2 = MONO_UNSIGNED_VALUE_FLAG|MONO_INTEGER_VALUE_SIZE_2,
 108         MONO_UNSIGNED_INTEGER_VALUE_SIZE_4 = MONO_UNSIGNED_VALUE_FLAG|MONO_INTEGER_VALUE_SIZE_4,
 109         MONO_UNSIGNED_INTEGER_VALUE_SIZE_8 = MONO_UNSIGNED_VALUE_FLAG|MONO_INTEGER_VALUE_SIZE_8,
 110         MONO_UNKNOWN_INTEGER_VALUE = 0
 111 } MonoIntegerValueKind;
 112
 113 /**
 114  * A relation between variables (or a variable and a constant).
 115  * The first variable (the one "on the left of the expression") is implicit.
 116  * relation: the relation between the variable and the value
 117  * related_value: the related value
 118  * relation_is_static_definition: TRUE if the relation comes from a veriable
 119  *                                definition, FALSE if it comes from a branch
 120  *                                condition
 121  * next: pointer to the next relation of this variable in the evaluation area
 122  *       (relations are always kept in the evaluation area, one list for each
 123  *       variable)
 124  */
 125 typedef struct MonoSummarizedValueRelation {
 126         MonoValueRelation relation;
 127         MonoSummarizedValue related_value;
 128         gboolean relation_is_static_definition;
 129         struct MonoSummarizedValueRelation *next;
 130 } MonoSummarizedValueRelation;
 131
 132 /**
 133  * The evaluation status for one variable.
 134  * The enumeration is used as a bit field, because the status has two
 135  * distinct sections.
 136  * The first is the "main" one (bits 0, 1 and 2), which is actually a proper
 137  * enumeration (the bits are mutually exclusive, and their meaning is obvious).
 138  * The other section (the bits in the MONO_RELATIONS_EVALUATION_IS_RECURSIVE
 139  * set) is used to mark an evaluation as recursive (while backtracking through
 140  * the evaluation contexts), to state if the graph loop gives a value that is
 141  * ascending, descending or indefinite.
 142  * The bits are handled separately because the same evaluation context could
 143  * belong to more than one loop, so that each loop would set its bits.
 144  * After the backtracking, the bits are examined and a decision is taken.
 145  *
 146  */
 147 typedef enum {
 148         MONO_RELATIONS_EVALUATION_NOT_STARTED = 0,
 149         MONO_RELATIONS_EVALUATION_IN_PROGRESS = 1,
 150         MONO_RELATIONS_EVALUATION_COMPLETED = 2,
 151         MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_ASCENDING = 4,
 152         MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_DESCENDING = 8,
 153         MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_INDEFINITE = 16,
 154         MONO_RELATIONS_EVALUATION_IS_RECURSIVE = (MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_ASCENDING|MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_DESCENDING|MONO_RELATIONS_EVALUATION_IS_RECURSIVELY_INDEFINITE)
 155 } MonoRelationsEvaluationStatus;
 156
 157 /**
 158  * A range of values (ranges include their limits).
 159  * A range from MIN_INT to MAX_INT is "indefinite" (any value).
 160  * A range where upper < lower means unreachable code (some of the relations
 161  * that generated the range is incompatible, like x = 0 and x > 0).
 162  * lower: the lower limit
 163  * upper: the upper limit
 164  */
 165 typedef struct MonoRelationsEvaluationRange {
 166         int lower;
 167         int upper;
 168 } MonoRelationsEvaluationRange;
 169
 170 /**
 171  * The two ranges that contain the result of a variable evaluation.
 172  * zero: the range with respect to zero
 173  * variable: the range with respect to the target variable in this evaluation
 174  */
 175 typedef struct MonoRelationsEvaluationRanges {
 176         MonoRelationsEvaluationRange zero;
 177         MonoRelationsEvaluationRange variable;
 178 } MonoRelationsEvaluationRanges;
 179
 180 /**
 181  * The context of a variable evaluation.
 182  * status: the evaluation status
 183  * current_relation: the relation that is currently evaluated.
 184  * ranges: the result of the evaluation.
 185  * father: the context of the evaluation that invoked this one (used to
 186  *         perform the backtracking when loops are detected.
 187  */
 188 typedef struct MonoRelationsEvaluationContext {
 189         MonoRelationsEvaluationStatus status;
 190         MonoSummarizedValueRelation *current_relation;
 191         MonoRelationsEvaluationRanges ranges;
 192         struct MonoRelationsEvaluationContext *father;
 193 } MonoRelationsEvaluationContext;
 194
 195 /*
 196  * Basic macros to initialize and check ranges.
 197  */
 198 #define MONO_MAKE_RELATIONS_EVALUATION_RANGE_WEAK(r) do{\
 199                 (r).lower = INT_MIN;\
 200                 (r).upper = INT_MAX;\
 201         } while (0)
 202 #define MONO_MAKE_RELATIONS_EVALUATION_RANGES_WEAK(rs) do{\
 203                 MONO_MAKE_RELATIONS_EVALUATION_RANGE_WEAK ((rs).zero); \
 204                 MONO_MAKE_RELATIONS_EVALUATION_RANGE_WEAK ((rs).variable); \
 205         } while (0)
 206 #define MONO_MAKE_RELATIONS_EVALUATION_RANGE_IMPOSSIBLE(r) do{\
 207                 (r).lower = INT_MAX;\
 208                 (r).upper = INT_MIN;\
 209         } while (0)
 210 #define MONO_MAKE_RELATIONS_EVALUATION_RANGES_IMPOSSIBLE(rs) do{\
 211                 MONO_MAKE_RELATIONS_EVALUATION_RANGE_IMPOSSIBLE ((rs).zero); \
 212                 MONO_MAKE_RELATIONS_EVALUATION_RANGE_IMPOSSIBLE ((rs).variable); \
 213         } while (0)
 214 #define MONO_RELATIONS_EVALUATION_RANGE_IS_WEAK(r) (((r).lower==INT_MIN)&&((r).upper==INT_MAX))
 215 #define MONO_RELATIONS_EVALUATION_RANGES_ARE_WEAK(rs) \
 216         (MONO_RELATIONS_EVALUATION_RANGE_IS_WEAK((rs).zero) && \
 217         MONO_RELATIONS_EVALUATION_RANGE_IS_WEAK((rs).variable))
 218 #define MONO_RELATIONS_EVALUATION_RANGE_IS_IMPOSSIBLE(r) (((r).lower)>((r).upper))
 219 #define MONO_RELATIONS_EVALUATION_RANGES_ARE_IMPOSSIBLE(rs) \
 220         (MONO_RELATIONS_EVALUATION_RANGE_IS_IMPOSSIBLE((rs).zero) || \
 221         MONO_RELATIONS_EVALUATION_RANGE_IS_IMPOSSIBLE((rs).variable))
 222
 223 /*
 224  * The following macros are needed because ranges include theit limits, but
 225  * some relations explicitly exclude them (GT and LT).
 226  */
 227 #define MONO_UPPER_EVALUATION_RANGE_NOT_EQUAL(ur) ((((ur)==INT_MIN)||((ur)==INT_MAX))?(ur):((ur)-1))
 228 #define MONO_LOWER_EVALUATION_RANGE_NOT_EQUAL(lr) ((((lr)==INT_MIN)||((lr)==INT_MAX))?(lr):((lr)+1))
 229 #define MONO_APPLY_INEQUALITY_TO_EVALUATION_RANGE(r) do{\
 230                 (r).lower = MONO_LOWER_EVALUATION_RANGE_NOT_EQUAL ((r).lower);\
 231                 (r).upper = MONO_UPPER_EVALUATION_RANGE_NOT_EQUAL ((r).upper);\
 232         } while (0)
 233 #define MONO_APPLY_INEQUALITY_TO_EVALUATION_RANGES(rs) do{\
 234                 MONO_APPLY_INEQUALITY_TO_EVALUATION_RANGE ((rs).zero); \
 235                 MONO_APPLY_INEQUALITY_TO_EVALUATION_RANGE ((rs).variable); \
 236         } while (0)
 237
 238 /*
 239  * The following macros perform union and intersection operations on ranges.
 240  */
 241 #define MONO_LOWER_EVALUATION_RANGE_UNION(lr,other_lr) ((lr)=MIN(lr,other_lr))
 242 #define MONO_UPPER_EVALUATION_RANGE_UNION(ur,other_ur) ((ur)=MAX(ur,other_ur))
 243 #define MONO_LOWER_EVALUATION_RANGE_INTERSECTION(lr,other_lr) ((lr)=MAX(lr,other_lr))
 244 #define MONO_UPPER_EVALUATION_RANGE_INTERSECTION(ur,other_ur) ((ur)=MIN(ur,other_ur))
 245 #define MONO_RELATIONS_EVALUATION_RANGE_UNION(r,other_r) do{\
 246                 MONO_LOWER_EVALUATION_RANGE_UNION((r).lower,(other_r).lower);\
 247                 MONO_UPPER_EVALUATION_RANGE_UNION((r).upper,(other_r).upper);\
 248         } while (0)
 249 #define MONO_RELATIONS_EVALUATION_RANGE_INTERSECTION(r,other_r) do{\
 250                 MONO_LOWER_EVALUATION_RANGE_INTERSECTION((r).lower,(other_r).lower);\
 251                 MONO_UPPER_EVALUATION_RANGE_INTERSECTION((r).upper,(other_r).upper);\
 252         } while (0)
 253 #define MONO_RELATIONS_EVALUATION_RANGES_UNION(rs,other_rs) do{\
 254                 MONO_RELATIONS_EVALUATION_RANGE_UNION ((rs).zero,(other_rs).zero); \
 255                 MONO_RELATIONS_EVALUATION_RANGE_UNION ((rs).variable,(other_rs).variable); \
 256         } while (0)
 257 #define MONO_RELATIONS_EVALUATION_RANGES_INTERSECTION(rs,other_rs) do{\
 258                 MONO_RELATIONS_EVALUATION_RANGE_INTERSECTION ((rs).zero,(other_rs).zero); \
 259                 MONO_RELATIONS_EVALUATION_RANGE_INTERSECTION ((rs).variable,(other_rs).variable); \
 260         } while (0)
 261
 262 /*
 263  * The following macros add or subtract "safely" (without over/under-flow) a
 264  * delta (constant) value to a range.
 265  */
 266 #define MONO_ADD_DELTA_SAFELY(v,d) do{\
 267                 if (((d) > 0) && ((v) != INT_MIN)) {\
 268                         (v) = (((v)+(d))>(v))?((v)+(d)):INT_MAX;\
 269                 } else if (((d) < 0) && ((v) != INT_MAX)) {\
 270                         (v) = (((v)+(d))<(v))?((v)+(d)):INT_MIN;\
 271                 }\
 272         } while (0)
 273 #define MONO_SUB_DELTA_SAFELY(v,d) do{\
 274                 if (((d) < 0) && ((v) != INT_MIN)) {\
 275                         (v) = (((v)-(d))>(v))?((v)-(d)):INT_MAX;\
 276                 } else if (((d) > 0) && ((v) != INT_MAX)) {\
 277                         (v) = (((v)-(d))<(v))?((v)-(d)):INT_MIN;\
 278                 }\
 279         } while (0)
 280 #define MONO_ADD_DELTA_SAFELY_TO_RANGE(r,d) do{\
 281                 MONO_ADD_DELTA_SAFELY((r).lower,(d));\
 282                 MONO_ADD_DELTA_SAFELY((r).upper,(d));\
 283         } while (0)
 284 #define MONO_SUB_DELTA_SAFELY_FROM_RANGE(r,d) do{\
 285                 MONO_SUB_DELTA_SAFELY((r).lower,(d));\
 286                 MONO_SUB_DELTA_SAFELY((r).upper,(d));\
 287         } while (0)
 288 #define MONO_ADD_DELTA_SAFELY_TO_RANGES(rs,d) do{\
 289                 MONO_ADD_DELTA_SAFELY_TO_RANGE((rs).zero,(d));\
 290                 MONO_ADD_DELTA_SAFELY_TO_RANGE((rs).variable,(d));\
 291         } while (0)
 292 #define MONO_SUB_DELTA_SAFELY_FROM_RANGES(rs,d) do{\
 293                 MONO_SUB_DELTA_SAFELY_FROM_RANGE((rs).zero,(d));\
 294                 MONO_SUB_DELTA_SAFELY_FROM_RANGE((rs).variable,(d));\
 295         } while (0)
 296
 297
 298 /**
 299  * The main evaluation area.
 300  * cfg: the cfg of the method that is being examined.
 301  * relations: and array of relations, one for each method variable (each
 302  *            relation is the head of a list); this is the evaluation graph
 303  * contexts: an array of evaluation contexts (one for each method variable)
 304  * variable_value_kind: an array of MonoIntegerValueKind, one for each local
 305  *                      variable (or argument)
 306  * defs: maps vregs to the instruction which defines it.
 307  */
 308 typedef struct MonoVariableRelationsEvaluationArea {
 309         MonoCompile *cfg;
 310         MonoSummarizedValueRelation *relations;
 311         MonoRelationsEvaluationContext *contexts;
 312         MonoIntegerValueKind *variable_value_kind;
 313         MonoInst **defs;
 314 } MonoVariableRelationsEvaluationArea;
 315
 316 /**
 317  * Convenience structure to define an "additional" relation for the main
 318  * evaluation graph.
 319  * variable: the variable to which the relation is applied
 320  * relation: the relation
 321  * insertion_point: the point in the graph where the relation is inserted
 322  *                  (useful for removing it from the list when backtracking
 323  *                  in the traversal of the dominator tree)
 324  */
 325 typedef struct MonoAdditionalVariableRelation {
 326         int variable;
 327         MonoSummarizedValueRelation relation;
 328         MonoSummarizedValueRelation *insertion_point;
 329 } MonoAdditionalVariableRelation;
 330
 331 /**
 332  * Convenience structure that stores two additional relations.
 333  * In the current code, each BB can add at most two relations to the main
 334  * evaluation graph, so one of these structures is enough to hold all the
 335  * modifications to the graph made examining one BB.
 336  */
 337 typedef struct MonoAdditionalVariableRelationsForBB {
 338         MonoAdditionalVariableRelation relation1;
 339         MonoAdditionalVariableRelation relation2;
 340 } MonoAdditionalVariableRelationsForBB;
 341
 342
 343 #endif /* __MONO_ABCREMOVAL_H__ */