Halide 19.0.0
Halide compiler and libraries
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Simplify_Internal.h
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1#ifndef HALIDE_SIMPLIFY_VISITORS_H
2#define HALIDE_SIMPLIFY_VISITORS_H
3
4/** \file
5 * The simplifier is separated into multiple compilation units with
6 * this single shared header to speed up the build. This file is not
7 * exported in Halide.h. */
8
9#include "Bounds.h"
10#include "ConstantInterval.h"
11#include "IRMatch.h"
12#include "IRPrinter.h"
13#include "IRVisitor.h"
14#include "Scope.h"
15
16// Because this file is only included by the simplify methods and
17// doesn't go into Halide.h, we're free to use any old names for our
18// macros.
19
20#define LOG_EXPR_MUTATIONS 0
21#define LOG_STMT_MUTATIONS 0
22
23// On old compilers, some visitors would use large stack frames,
24// because they use expression templates that generate large numbers
25// of temporary objects when they are built and matched against. If we
26// wrap the expressions that imply lots of temporaries in a lambda, we
27// can get these large frames out of the recursive path.
28#define EVAL_IN_LAMBDA(x) (([&]() HALIDE_NEVER_INLINE { return (x); })())
29
30namespace Halide {
31namespace Internal {
32
33class Simplify : public VariadicVisitor<Simplify, Expr, Stmt> {
35
36public:
37 Simplify(bool r, const Scope<Interval> *bi, const Scope<ModulusRemainder> *ai);
38
39 struct ExprInfo {
40 // We track constant integer bounds when they exist
42 // And the alignment of integer variables
44
46 if (alignment.modulus == 0) {
48 } else if (alignment.modulus > 1) {
49 if (bounds.min_defined) {
50 int64_t adjustment;
52 adjustment = mod_imp(adjustment, alignment.modulus);
53 int64_t new_min;
54 no_overflow &= add_with_overflow(64, bounds.min, adjustment, &new_min);
55 if (no_overflow) {
56 bounds.min = new_min;
57 }
58 }
59 if (bounds.max_defined) {
60 int64_t adjustment;
62 adjustment = mod_imp(adjustment, alignment.modulus);
63 int64_t new_max;
64 no_overflow &= sub_with_overflow(64, bounds.max, adjustment, &new_max);
65 if (no_overflow) {
66 bounds.max = new_max;
67 }
68 }
69 }
70
71 if (bounds.is_single_point()) {
74 }
75
76 if (bounds.is_bounded() && bounds.min > bounds.max) {
77 // Impossible, we must be in unreachable code. TODO: surface
78 // this to the simplify instance's in_unreachable flag.
80 }
81 }
82
83 void cast_to(Type t) {
84 if ((!t.is_int() && !t.is_uint()) || (t.is_int() && t.bits() >= 32)) {
85 return;
86 }
87
88 // We've just done some infinite-integer operation on a bounded
89 // integer type, and we need to project the bounds and alignment
90 // back in-range.
91
92 if (!t.can_represent(bounds)) {
93 if (t.bits() >= 64) {
94 // Just preserve any power-of-two factor in the modulus. When
95 // alignment.modulus == 0, the value is some positive constant
96 // representable as any 64-bit integer type, so there's no
97 // wraparound.
98 if (alignment.modulus > 0) {
99 // This masks off all bits except for the lowest set one,
100 // giving the largest power-of-two factor of a number.
103 }
104 } else {
105 // A narrowing integer cast that could possibly overflow adds
106 // some unknown multiple of 2^bits
107 alignment = alignment + ModulusRemainder(((int64_t)1 << t.bits()), 0);
108 }
109 }
110
111 // Truncate the bounds to the new type.
112 bounds.cast_to(t);
113 }
114
115 // Mix in existing knowledge about this Expr
116 void intersect(const ExprInfo &other) {
117 if (bounds < other.bounds || other.bounds < bounds) {
118 // Impossible. We must be in unreachable code. TODO: It might
119 // be nice to surface this to the simplify instance's
120 // in_unreachable flag, but we'd have to be sure that it's going
121 // to be caught at the right place.
122 return;
123 }
127 }
128 };
129
132 if (b) {
133 *b = ExprInfo{};
134 }
135 }
136
137#if (LOG_EXPR_MUTATIONS || LOG_STMT_MUTATIONS)
138 int debug_indent = 0;
139#endif
140
141#if LOG_EXPR_MUTATIONS
142 Expr mutate(const Expr &e, ExprInfo *b) {
143 internal_assert(debug_indent >= 0);
144 const std::string spaces(debug_indent, ' ');
145 debug(1) << spaces << "Simplifying Expr: " << e << "\n";
146 debug_indent++;
147 Expr new_e = Super::dispatch(e, b);
148 debug_indent--;
149 if (!new_e.same_as(e)) {
150 debug(1)
151 << spaces << "Before: " << e << "\n"
152 << spaces << "After: " << new_e << "\n";
153 if (b) {
154 debug(1)
155 << spaces << "Bounds: " << b->bounds << " " << b->alignment << "\n";
156 if (const int64_t *i = as_const_int(new_e)) {
157 internal_assert(b->bounds.contains(*i)) << e << "\n"
158 << new_e << "\n"
159 << b->bounds;
160 } else if (const uint64_t *i = as_const_uint(new_e)) {
161 internal_assert(b->bounds.contains(*i)) << e << "\n"
162 << new_e << "\n"
163 << b->bounds;
164 }
165 }
166 }
167 internal_assert(e.type() == new_e.type());
168 return new_e;
169 }
170
171#else
173 Expr mutate(const Expr &e, ExprInfo *b) {
174 // This gets inlined into every call to mutate, so do not add any code here.
175 return Super::dispatch(e, b);
176 }
177#endif
178
179#if LOG_STMT_MUTATIONS
180 Stmt mutate(const Stmt &s) {
181 const std::string spaces(debug_indent, ' ');
182 debug(1) << spaces << "Simplifying Stmt: " << s << "\n";
183 debug_indent++;
184 Stmt new_s = Super::dispatch(s);
185 debug_indent--;
186 if (!new_s.same_as(s)) {
187 debug(1)
188 << spaces << "Before: " << s << "\n"
189 << spaces << "After: " << new_s << "\n";
190 }
191 return new_s;
192 }
193#else
194 Stmt mutate(const Stmt &s) {
195 return Super::dispatch(s);
196 }
197#endif
198
200 bool no_float_simplify = false;
201
203 bool may_simplify(const Type &t) const {
204 return !no_float_simplify || !t.is_float();
205 }
206
207 // Returns true iff t is an integral type where overflow is undefined
210 return t.is_int() && t.bits() >= 32;
211 }
212
215 return t.is_scalar() && no_overflow_int(t);
216 }
217
218 // Returns true iff t does not have a well defined overflow behavior.
221 return t.is_float() || no_overflow_int(t);
222 }
223
228
229 // Tracked for all let vars
231
232 // Only tracked for integer let vars
234
235 // Symbols used by rewrite rules
248
249 // Tracks whether or not we're inside a vector loop. Certain
250 // transformations are not a good idea if the code is to be
251 // vectorized.
252 bool in_vector_loop = false;
253
254 // Tracks whether or not the current IR is unconditionally unreachable.
255 bool in_unreachable = false;
256
257 // If we encounter a reference to a buffer (a Load, Store, Call,
258 // or Provide), there's an implicit dependence on some associated
259 // symbols.
260 void found_buffer_reference(const std::string &name, size_t dimensions = 0);
261
262 // Wrappers for as_const_foo that are more convenient to use in
263 // the large chains of conditions in the visit methods below.
264 bool const_float(const Expr &e, double *f);
265 bool const_int(const Expr &e, int64_t *i);
266 bool const_uint(const Expr &e, uint64_t *u);
267
268 // Put the args to a commutative op in a canonical order
270 bool should_commute(const Expr &a, const Expr &b) {
271 if (a.node_type() < b.node_type()) {
272 return true;
273 }
274 if (a.node_type() > b.node_type()) {
275 return false;
276 }
277
278 if (a.node_type() == IRNodeType::Variable) {
279 const Variable *va = a.as<Variable>();
280 const Variable *vb = b.as<Variable>();
281 return va->name.compare(vb->name) > 0;
282 }
283
284 return false;
285 }
286
287 std::set<Expr, IRDeepCompare> truths, falsehoods;
288
289 struct ScopedFact {
291
292 std::vector<const Variable *> pop_list;
293 std::vector<const Variable *> bounds_pop_list;
294 std::set<Expr, IRDeepCompare> truths, falsehoods;
295
296 void learn_false(const Expr &fact);
297 void learn_true(const Expr &fact);
300
301 // Replace exprs known to be truths or falsehoods with const_true or const_false.
304
306 : simplify(s) {
307 }
309
310 // allow move but not copy
311 ScopedFact(const ScopedFact &that) = delete;
312 ScopedFact(ScopedFact &&that) = default;
313 };
314
315 // Tell the simplifier to learn from and exploit a boolean
316 // condition, over the lifetime of the returned object.
318 ScopedFact f(this);
319 f.learn_true(fact);
320 return f;
321 }
322
323 // Tell the simplifier to assume a boolean condition is false over
324 // the lifetime of the returned object.
326 ScopedFact f(this);
327 f.learn_false(fact);
328 return f;
329 }
330
332 return mutate(s);
333 }
335 return mutate(e, info);
336 }
337
338 template<typename T, typename Body>
339 Body simplify_let(const T *op, ExprInfo *info);
340
341 Expr visit(const IntImm *op, ExprInfo *info);
342 Expr visit(const UIntImm *op, ExprInfo *info);
343 Expr visit(const FloatImm *op, ExprInfo *info);
344 Expr visit(const StringImm *op, ExprInfo *info);
345 Expr visit(const Broadcast *op, ExprInfo *info);
346 Expr visit(const Cast *op, ExprInfo *info);
347 Expr visit(const Reinterpret *op, ExprInfo *info);
348 Expr visit(const Variable *op, ExprInfo *info);
349 Expr visit(const Add *op, ExprInfo *info);
350 Expr visit(const Sub *op, ExprInfo *info);
351 Expr visit(const Mul *op, ExprInfo *info);
352 Expr visit(const Div *op, ExprInfo *info);
353 Expr visit(const Mod *op, ExprInfo *info);
354 Expr visit(const Min *op, ExprInfo *info);
355 Expr visit(const Max *op, ExprInfo *info);
356 Expr visit(const EQ *op, ExprInfo *info);
357 Expr visit(const NE *op, ExprInfo *info);
358 Expr visit(const LT *op, ExprInfo *info);
359 Expr visit(const LE *op, ExprInfo *info);
360 Expr visit(const GT *op, ExprInfo *info);
361 Expr visit(const GE *op, ExprInfo *info);
362 Expr visit(const And *op, ExprInfo *info);
363 Expr visit(const Or *op, ExprInfo *info);
364 Expr visit(const Not *op, ExprInfo *info);
365 Expr visit(const Select *op, ExprInfo *info);
366 Expr visit(const Ramp *op, ExprInfo *info);
368 Expr visit(const Load *op, ExprInfo *info);
369 Expr visit(const Call *op, ExprInfo *info);
370 Expr visit(const Shuffle *op, ExprInfo *info);
371 Expr visit(const VectorReduce *op, ExprInfo *info);
372 Expr visit(const Let *op, ExprInfo *info);
373 Stmt visit(const LetStmt *op);
375 Stmt visit(const For *op);
376 Stmt visit(const Provide *op);
377 Stmt visit(const Store *op);
378 Stmt visit(const Allocate *op);
379 Stmt visit(const Evaluate *op);
381 Stmt visit(const Block *op);
382 Stmt visit(const Realize *op);
383 Stmt visit(const Prefetch *op);
384 Stmt visit(const Free *op);
385 Stmt visit(const Acquire *op);
386 Stmt visit(const Fork *op);
387 Stmt visit(const Atomic *op);
389
390 std::pair<std::vector<Expr>, bool> mutate_with_changes(const std::vector<Expr> &old_exprs);
391};
392
393} // namespace Internal
394} // namespace Halide
395
396#endif
Methods for computing the upper and lower bounds of an expression, and the regions of a function read...
Defines the ConstantInterval class, and operators on it.
#define internal_assert(c)
Definition Errors.h:19
#define HALIDE_ALWAYS_INLINE
Defines a method to match a fragment of IR against a pattern containing wildcards.
This header file defines operators that let you dump a Halide expression, statement,...
Defines the base class for things that recursively walk over the IR.
Defines the Scope class, which is used for keeping track of names in a scope while traversing IR.
A common pattern when traversing Halide IR is that you need to keep track of stuff when you find a Le...
Definition Scope.h:94
Stmt visit(const HoistedStorage *op)
Expr visit(const LE *op, ExprInfo *info)
Stmt visit(const ProducerConsumer *op)
HALIDE_ALWAYS_INLINE Expr mutate(const Expr &e, ExprInfo *b)
Scope< ExprInfo > bounds_and_alignment_info
bool const_uint(const Expr &e, uint64_t *u)
Expr visit(const Variable *op, ExprInfo *info)
IRMatcher::WildConst< 5 > c5
void found_buffer_reference(const std::string &name, size_t dimensions=0)
Stmt visit(const Block *op)
Expr visit(const Load *op, ExprInfo *info)
Expr visit(const Cast *op, ExprInfo *info)
Stmt visit(const AssertStmt *op)
Stmt visit(const Evaluate *op)
Expr visit(const Let *op, ExprInfo *info)
Expr visit(const LT *op, ExprInfo *info)
Simplify(bool r, const Scope< Interval > *bi, const Scope< ModulusRemainder > *ai)
Expr visit(const Ramp *op, ExprInfo *info)
Stmt visit(const Prefetch *op)
HALIDE_ALWAYS_INLINE bool no_overflow(Type t)
IRMatcher::WildConst< 1 > c1
Expr visit(const Shuffle *op, ExprInfo *info)
Stmt visit(const IfThenElse *op)
Expr visit(const Mod *op, ExprInfo *info)
IRMatcher::WildConst< 0 > c0
ScopedFact scoped_truth(const Expr &fact)
IRMatcher::WildConst< 3 > c3
Expr visit(const UIntImm *op, ExprInfo *info)
Expr visit(const Add *op, ExprInfo *info)
Expr visit(const Max *op, ExprInfo *info)
HALIDE_ALWAYS_INLINE void clear_expr_info(ExprInfo *b)
Expr visit(const Mul *op, ExprInfo *info)
IRMatcher::WildConst< 2 > c2
Expr visit(const StringImm *op, ExprInfo *info)
Expr visit(const VectorReduce *op, ExprInfo *info)
Expr visit(const Min *op, ExprInfo *info)
Expr visit(const Reinterpret *op, ExprInfo *info)
Expr visit(const NE *op, ExprInfo *info)
HALIDE_ALWAYS_INLINE bool may_simplify(const Type &t) const
Stmt visit(const For *op)
Expr visit(const Select *op, ExprInfo *info)
Stmt visit(const Atomic *op)
Expr visit(const Div *op, ExprInfo *info)
bool const_float(const Expr &e, double *f)
Expr visit(const GE *op, ExprInfo *info)
Stmt visit(const Provide *op)
Expr visit(const Not *op, ExprInfo *info)
Body simplify_let(const T *op, ExprInfo *info)
Expr mutate_let_body(const Expr &e, ExprInfo *info)
Expr visit(const Or *op, ExprInfo *info)
Expr visit(const FloatImm *op, ExprInfo *info)
Stmt mutate_let_body(const Stmt &s, ExprInfo *)
Stmt visit(const Acquire *op)
Stmt visit(const Fork *op)
HALIDE_ALWAYS_INLINE bool no_overflow_int(Type t)
std::set< Expr, IRDeepCompare > truths
ScopedFact scoped_falsehood(const Expr &fact)
HALIDE_ALWAYS_INLINE bool should_commute(const Expr &a, const Expr &b)
Expr visit(const Broadcast *op, ExprInfo *info)
Expr visit(const Sub *op, ExprInfo *info)
std::pair< std::vector< Expr >, bool > mutate_with_changes(const std::vector< Expr > &old_exprs)
Stmt visit(const Store *op)
Expr visit(const GT *op, ExprInfo *info)
HALIDE_ALWAYS_INLINE bool no_overflow_scalar_int(Type t)
bool const_int(const Expr &e, int64_t *i)
Stmt visit(const Free *op)
IRMatcher::WildConst< 4 > c4
Expr visit(const Call *op, ExprInfo *info)
Stmt visit(const Allocate *op)
Stmt visit(const Realize *op)
Expr visit(const EQ *op, ExprInfo *info)
Stmt visit(const LetStmt *op)
std::set< Expr, IRDeepCompare > falsehoods
Expr visit(const IntImm *op, ExprInfo *info)
Expr visit(const And *op, ExprInfo *info)
A visitor/mutator capable of passing arbitrary arguments to the visit methods using CRTP and returnin...
Definition IRVisitor.h:161
HALIDE_ALWAYS_INLINE Stmt dispatch(const Stmt &s, Args &&...args)
Definition IRVisitor.h:335
For optional debugging during codegen, use the debug class as follows:
Definition Debug.h:49
const int64_t * as_const_int(const Expr &e)
If an expression is an IntImm or a Broadcast of an IntImm, return a pointer to its value.
T mod_imp(T a, T b)
Implementations of division and mod that are specific to Halide.
Definition IROperator.h:247
HALIDE_MUST_USE_RESULT bool add_with_overflow(int bits, int64_t a, int64_t b, int64_t *result)
Routines to perform arithmetic on signed types without triggering signed overflow.
const uint64_t * as_const_uint(const Expr &e)
If an expression is a UIntImm or a Broadcast of a UIntImm, return a pointer to its value.
HALIDE_MUST_USE_RESULT bool sub_with_overflow(int bits, int64_t a, int64_t b, int64_t *result)
This file defines the class FunctionDAG, which is our representation of a Halide pipeline,...
unsigned __INT64_TYPE__ uint64_t
signed __INT64_TYPE__ int64_t
A fragment of Halide syntax.
Definition Expr.h:258
HALIDE_ALWAYS_INLINE Type type() const
Get the type of this expression node.
Definition Expr.h:327
The sum of two expressions.
Definition IR.h:56
Allocate a scratch area called with the given name, type, and size.
Definition IR.h:371
Logical and - are both expressions true.
Definition IR.h:175
If the 'condition' is false, then evaluate and return the message, which should be a call to an error...
Definition IR.h:294
Lock all the Store nodes in the body statement.
Definition IR.h:961
A sequence of statements to be executed in-order.
Definition IR.h:442
A vector with 'lanes' elements, in which every element is 'value'.
Definition IR.h:259
A function call.
Definition IR.h:490
The actual IR nodes begin here.
Definition IR.h:30
A class to represent ranges of integers.
int64_t min
The lower and upper bound of the interval.
bool is_bounded() const
Does the interval have a finite upper and lower bound.
static ConstantInterval make_intersection(const ConstantInterval &a, const ConstantInterval &b)
Construct the largest interval contained within two intervals.
bool is_single_point() const
Is the interval just a single value (min == max)
void cast_to(const Type &t)
Track what happens if a constant integer interval is forced to fit into a concrete integer type.
static ConstantInterval single_point(int64_t x)
Construct an interval representing a single point.
The ratio of two expressions.
Definition IR.h:83
Is the first expression equal to the second.
Definition IR.h:121
Evaluate and discard an expression, presumably because it has some side-effect.
Definition IR.h:476
Floating point constants.
Definition Expr.h:236
A for loop.
Definition IR.h:819
A pair of statements executed concurrently.
Definition IR.h:457
Free the resources associated with the given buffer.
Definition IR.h:413
Is the first expression greater than or equal to the second.
Definition IR.h:166
Is the first expression greater than the second.
Definition IR.h:157
Represents a location where storage will be hoisted to for a Func / Realize node with a given name.
Definition IR.h:945
const T * as() const
Downcast this ir node to its actual type (e.g.
Definition Expr.h:205
IRNodeType node_type() const
Definition Expr.h:212
An if-then-else block.
Definition IR.h:466
Integer constants.
Definition Expr.h:218
HALIDE_ALWAYS_INLINE bool same_as(const IntrusivePtr &other) const
Is the first expression less than or equal to the second.
Definition IR.h:148
Is the first expression less than the second.
Definition IR.h:139
A let expression, like you might find in a functional language.
Definition IR.h:271
The statement form of a let node.
Definition IR.h:282
Load a value from a named symbol if predicate is true.
Definition IR.h:217
The greater of two values.
Definition IR.h:112
The lesser of two values.
Definition IR.h:103
The remainder of a / b.
Definition IR.h:94
The result of modulus_remainder analysis.
static ModulusRemainder intersect(const ModulusRemainder &a, const ModulusRemainder &b)
The product of two expressions.
Definition IR.h:74
Is the first expression not equal to the second.
Definition IR.h:130
Logical not - true if the expression false.
Definition IR.h:193
Logical or - is at least one of the expression true.
Definition IR.h:184
Represent a multi-dimensional region of a Func or an ImageParam that needs to be prefetched.
Definition IR.h:923
This node is a helpful annotation to do with permissions.
Definition IR.h:315
This defines the value of a function at a multi-dimensional location.
Definition IR.h:354
A linear ramp vector node.
Definition IR.h:247
Allocate a multi-dimensional buffer of the given type and size.
Definition IR.h:427
Reinterpret value as another type, without affecting any of the bits (on little-endian systems).
Definition IR.h:47
A ternary operator.
Definition IR.h:204
Construct a new vector by taking elements from another sequence of vectors.
Definition IR.h:855
void intersect(const ExprInfo &other)
ScopedFact(ScopedFact &&that)=default
void learn_false(const Expr &fact)
std::vector< const Variable * > bounds_pop_list
ScopedFact(const ScopedFact &that)=delete
std::set< Expr, IRDeepCompare > truths
std::vector< const Variable * > pop_list
void learn_lower_bound(const Variable *v, int64_t val)
std::set< Expr, IRDeepCompare > falsehoods
void learn_upper_bound(const Variable *v, int64_t val)
A reference-counted handle to a statement node.
Definition Expr.h:427
Store a 'value' to the buffer called 'name' at a given 'index' if 'predicate' is true.
Definition IR.h:333
String constants.
Definition Expr.h:245
The difference of two expressions.
Definition IR.h:65
Unsigned integer constants.
Definition Expr.h:227
A named variable.
Definition IR.h:772
std::string name
Definition IR.h:773
Horizontally reduce a vector to a scalar or narrower vector using the given commutative and associati...
Definition IR.h:979
Types in the halide type system.
Definition Type.h:283
HALIDE_ALWAYS_INLINE bool is_int() const
Is this type a signed integer type?
Definition Type.h:435
HALIDE_ALWAYS_INLINE bool is_uint() const
Is this type an unsigned integer type?
Definition Type.h:441
HALIDE_ALWAYS_INLINE int bits() const
Return the bit size of a single element of this type.
Definition Type.h:349
bool can_represent(Type other) const
Can this type represent all values of another type?
HALIDE_ALWAYS_INLINE bool is_scalar() const
Is this type a scalar type? (lanes() == 1).
Definition Type.h:417
HALIDE_ALWAYS_INLINE bool is_float() const
Is this type a floating point type (float or double).
Definition Type.h:423