Halide  17.0.2
Halide compiler and libraries
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 "IRMatch.h"
11 #include "IRVisitor.h"
12 #include "Scope.h"
13 
14 // Because this file is only included by the simplify methods and
15 // doesn't go into Halide.h, we're free to use any old names for our
16 // macros.
17 
18 #define LOG_EXPR_MUTATIONS 0
19 #define LOG_STMT_MUTATIONS 0
20 
21 // On old compilers, some visitors would use large stack frames,
22 // because they use expression templates that generate large numbers
23 // of temporary objects when they are built and matched against. If we
24 // wrap the expressions that imply lots of temporaries in a lambda, we
25 // can get these large frames out of the recursive path.
26 #define EVAL_IN_LAMBDA(x) (([&]() HALIDE_NEVER_INLINE { return (x); })())
27 
28 namespace Halide {
29 namespace Internal {
30 
32  int64_t result;
33  if (mul_with_overflow(64, a, b, &result)) {
34  return result;
35  } else if ((a > 0) == (b > 0)) {
36  return INT64_MAX;
37  } else {
38  return INT64_MIN;
39  }
40 }
41 
42 class Simplify : public VariadicVisitor<Simplify, Expr, Stmt> {
44 
45 public:
46  Simplify(bool r, const Scope<Interval> *bi, const Scope<ModulusRemainder> *ai);
47 
48  struct ExprInfo {
49  // We track constant integer bounds when they exist
50  // TODO: Use ConstantInterval?
51  int64_t min = 0, max = 0;
52  bool min_defined = false, max_defined = false;
53  // And the alignment of integer variables
55 
57  if (alignment.modulus == 0) {
58  min_defined = max_defined = true;
60  } else if (alignment.modulus > 1) {
61  if (min_defined) {
62  int64_t adjustment;
64  adjustment = mod_imp(adjustment, alignment.modulus);
65  int64_t new_min;
66  no_overflow &= add_with_overflow(64, min, adjustment, &new_min);
67  if (no_overflow) {
68  min = new_min;
69  }
70  }
71  if (max_defined) {
72  int64_t adjustment;
74  adjustment = mod_imp(adjustment, alignment.modulus);
75  int64_t new_max;
76  no_overflow &= sub_with_overflow(64, max, adjustment, &new_max);
77  if (no_overflow) {
78  max = new_max;
79  }
80  }
81  }
82 
83  if (min_defined && max_defined && min == max) {
84  alignment.modulus = 0;
86  }
87  }
88 
89  // Mix in existing knowledge about this Expr
90  void intersect(const ExprInfo &other) {
91  if (min_defined && other.min_defined) {
92  min = std::max(min, other.min);
93  } else if (other.min_defined) {
94  min_defined = true;
95  min = other.min;
96  }
97 
98  if (max_defined && other.max_defined) {
99  max = std::min(max, other.max);
100  } else if (other.max_defined) {
101  max_defined = true;
102  max = other.max;
103  }
104 
106 
108  }
109  };
110 
113  if (b) {
114  *b = ExprInfo{};
115  }
116  }
117 
118 #if (LOG_EXPR_MUTATIONS || LOG_STMT_MUTATIONS)
119  static int debug_indent;
120 #endif
121 
122 #if LOG_EXPR_MUTATIONS
123  Expr mutate(const Expr &e, ExprInfo *b) {
124  const std::string spaces(debug_indent, ' ');
125  debug(1) << spaces << "Simplifying Expr: " << e << "\n";
126  debug_indent++;
127  Expr new_e = Super::dispatch(e, b);
128  debug_indent--;
129  if (!new_e.same_as(e)) {
130  debug(1)
131  << spaces << "Before: " << e << "\n"
132  << spaces << "After: " << new_e << "\n";
133  }
134  internal_assert(e.type() == new_e.type());
135  return new_e;
136  }
137 
138 #else
140  Expr mutate(const Expr &e, ExprInfo *b) {
141  // This gets inlined into every call to mutate, so do not add any code here.
142  return Super::dispatch(e, b);
143  }
144 #endif
145 
146 #if LOG_STMT_MUTATIONS
147  Stmt mutate(const Stmt &s) {
148  const std::string spaces(debug_indent, ' ');
149  debug(1) << spaces << "Simplifying Stmt: " << s << "\n";
150  debug_indent++;
151  Stmt new_s = Super::dispatch(s);
152  debug_indent--;
153  if (!new_s.same_as(s)) {
154  debug(1)
155  << spaces << "Before: " << s << "\n"
156  << spaces << "After: " << new_s << "\n";
157  }
158  return new_s;
159  }
160 #else
161  Stmt mutate(const Stmt &s) {
162  return Super::dispatch(s);
163  }
164 #endif
165 
167  bool no_float_simplify = false;
168 
170  bool may_simplify(const Type &t) const {
171  return !no_float_simplify || !t.is_float();
172  }
173 
174  // Returns true iff t is an integral type where overflow is undefined
177  return t.is_int() && t.bits() >= 32;
178  }
179 
182  return t.is_scalar() && no_overflow_int(t);
183  }
184 
185  // Returns true iff t does not have a well defined overflow behavior.
187  bool no_overflow(Type t) {
188  return t.is_float() || no_overflow_int(t);
189  }
190 
191  struct VarInfo {
194  };
195 
196  // Tracked for all let vars
198 
199  // Only tracked for integer let vars
201 
202  // Symbols used by rewrite rules
215 
216  // Tracks whether or not we're inside a vector loop. Certain
217  // transformations are not a good idea if the code is to be
218  // vectorized.
219  bool in_vector_loop = false;
220 
221  // Tracks whether or not the current IR is unconditionally unreachable.
222  bool in_unreachable = false;
223 
224  // If we encounter a reference to a buffer (a Load, Store, Call,
225  // or Provide), there's an implicit dependence on some associated
226  // symbols.
227  void found_buffer_reference(const std::string &name, size_t dimensions = 0);
228 
229  // Wrappers for as_const_foo that are more convenient to use in
230  // the large chains of conditions in the visit methods below.
231  bool const_float(const Expr &e, double *f);
232  bool const_int(const Expr &e, int64_t *i);
233  bool const_uint(const Expr &e, uint64_t *u);
234 
235  // Put the args to a commutative op in a canonical order
237  bool should_commute(const Expr &a, const Expr &b) {
238  if (a.node_type() < b.node_type()) {
239  return true;
240  }
241  if (a.node_type() > b.node_type()) {
242  return false;
243  }
244 
245  if (a.node_type() == IRNodeType::Variable) {
246  const Variable *va = a.as<Variable>();
247  const Variable *vb = b.as<Variable>();
248  return va->name.compare(vb->name) > 0;
249  }
250 
251  return false;
252  }
253 
254  std::set<Expr, IRDeepCompare> truths, falsehoods;
255 
256  struct ScopedFact {
258 
259  std::vector<const Variable *> pop_list;
260  std::vector<const Variable *> bounds_pop_list;
261  std::vector<Expr> truths, falsehoods;
262 
263  void learn_false(const Expr &fact);
264  void learn_true(const Expr &fact);
265  void learn_upper_bound(const Variable *v, int64_t val);
266  void learn_lower_bound(const Variable *v, int64_t val);
267 
268  // Replace exprs known to be truths or falsehoods with const_true or const_false.
271 
273  : simplify(s) {
274  }
276 
277  // allow move but not copy
278  ScopedFact(const ScopedFact &that) = delete;
279  ScopedFact(ScopedFact &&that) = default;
280  };
281 
282  // Tell the simplifier to learn from and exploit a boolean
283  // condition, over the lifetime of the returned object.
284  ScopedFact scoped_truth(const Expr &fact) {
285  ScopedFact f(this);
286  f.learn_true(fact);
287  return f;
288  }
289 
290  // Tell the simplifier to assume a boolean condition is false over
291  // the lifetime of the returned object.
293  ScopedFact f(this);
294  f.learn_false(fact);
295  return f;
296  }
297 
299  return mutate(s);
300  }
301  Expr mutate_let_body(const Expr &e, ExprInfo *bounds) {
302  return mutate(e, bounds);
303  }
304 
305  template<typename T, typename Body>
306  Body simplify_let(const T *op, ExprInfo *bounds);
307 
308  Expr visit(const IntImm *op, ExprInfo *bounds);
309  Expr visit(const UIntImm *op, ExprInfo *bounds);
310  Expr visit(const FloatImm *op, ExprInfo *bounds);
311  Expr visit(const StringImm *op, ExprInfo *bounds);
312  Expr visit(const Broadcast *op, ExprInfo *bounds);
313  Expr visit(const Cast *op, ExprInfo *bounds);
314  Expr visit(const Reinterpret *op, ExprInfo *bounds);
315  Expr visit(const Variable *op, ExprInfo *bounds);
316  Expr visit(const Add *op, ExprInfo *bounds);
317  Expr visit(const Sub *op, ExprInfo *bounds);
318  Expr visit(const Mul *op, ExprInfo *bounds);
319  Expr visit(const Div *op, ExprInfo *bounds);
320  Expr visit(const Mod *op, ExprInfo *bounds);
321  Expr visit(const Min *op, ExprInfo *bounds);
322  Expr visit(const Max *op, ExprInfo *bounds);
323  Expr visit(const EQ *op, ExprInfo *bounds);
324  Expr visit(const NE *op, ExprInfo *bounds);
325  Expr visit(const LT *op, ExprInfo *bounds);
326  Expr visit(const LE *op, ExprInfo *bounds);
327  Expr visit(const GT *op, ExprInfo *bounds);
328  Expr visit(const GE *op, ExprInfo *bounds);
329  Expr visit(const And *op, ExprInfo *bounds);
330  Expr visit(const Or *op, ExprInfo *bounds);
331  Expr visit(const Not *op, ExprInfo *bounds);
332  Expr visit(const Select *op, ExprInfo *bounds);
333  Expr visit(const Ramp *op, ExprInfo *bounds);
334  Stmt visit(const IfThenElse *op);
335  Expr visit(const Load *op, ExprInfo *bounds);
336  Expr visit(const Call *op, ExprInfo *bounds);
337  Expr visit(const Shuffle *op, ExprInfo *bounds);
338  Expr visit(const VectorReduce *op, ExprInfo *bounds);
339  Expr visit(const Let *op, ExprInfo *bounds);
340  Stmt visit(const LetStmt *op);
341  Stmt visit(const AssertStmt *op);
342  Stmt visit(const For *op);
343  Stmt visit(const Provide *op);
344  Stmt visit(const Store *op);
345  Stmt visit(const Allocate *op);
346  Stmt visit(const Evaluate *op);
348  Stmt visit(const Block *op);
349  Stmt visit(const Realize *op);
350  Stmt visit(const Prefetch *op);
351  Stmt visit(const Free *op);
352  Stmt visit(const Acquire *op);
353  Stmt visit(const Fork *op);
354  Stmt visit(const Atomic *op);
356 
357  std::pair<std::vector<Expr>, bool> mutate_with_changes(const std::vector<Expr> &old_exprs, ExprInfo *bounds);
358 };
359 
360 } // namespace Internal
361 } // namespace Halide
362 
363 #endif
Methods for computing the upper and lower bounds of an expression, and the regions of a function read...
#define internal_assert(c)
Definition: Errors.h:19
#define HALIDE_ALWAYS_INLINE
Definition: HalideRuntime.h:49
Defines a method to match a fragment of IR against a pattern containing wildcards.
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 Min *op, ExprInfo *bounds)
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)
IRMatcher::WildConst< 5 > c5
void found_buffer_reference(const std::string &name, size_t dimensions=0)
Expr visit(const Cast *op, ExprInfo *bounds)
Expr visit(const LT *op, ExprInfo *bounds)
Stmt visit(const Block *op)
Expr visit(const VectorReduce *op, ExprInfo *bounds)
Stmt visit(const AssertStmt *op)
Expr visit(const UIntImm *op, ExprInfo *bounds)
Stmt mutate(const Stmt &s)
HALIDE_ALWAYS_INLINE void clear_bounds_info(ExprInfo *b)
Expr visit(const Load *op, ExprInfo *bounds)
Stmt visit(const Evaluate *op)
Expr visit(const Not *op, ExprInfo *bounds)
Body simplify_let(const T *op, ExprInfo *bounds)
Simplify(bool r, const Scope< Interval > *bi, const Scope< ModulusRemainder > *ai)
Stmt visit(const Prefetch *op)
HALIDE_ALWAYS_INLINE bool no_overflow(Type t)
Expr visit(const Div *op, ExprInfo *bounds)
IRMatcher::WildConst< 1 > c1
Expr visit(const Let *op, ExprInfo *bounds)
Expr visit(const Reinterpret *op, ExprInfo *bounds)
Expr visit(const And *op, ExprInfo *bounds)
Stmt visit(const IfThenElse *op)
Expr visit(const NE *op, ExprInfo *bounds)
Expr visit(const FloatImm *op, ExprInfo *bounds)
Expr visit(const Shuffle *op, ExprInfo *bounds)
Expr visit(const Add *op, ExprInfo *bounds)
IRMatcher::WildConst< 0 > c0
ScopedFact scoped_truth(const Expr &fact)
IRMatcher::WildConst< 3 > c3
IRMatcher::WildConst< 2 > c2
Expr visit(const Ramp *op, ExprInfo *bounds)
Expr visit(const IntImm *op, ExprInfo *bounds)
Expr visit(const Max *op, ExprInfo *bounds)
Expr visit(const Variable *op, ExprInfo *bounds)
HALIDE_ALWAYS_INLINE bool may_simplify(const Type &t) const
Stmt visit(const For *op)
Stmt visit(const Atomic *op)
bool const_float(const Expr &e, double *f)
Expr visit(const GT *op, ExprInfo *bounds)
Stmt visit(const Provide *op)
Expr visit(const Sub *op, ExprInfo *bounds)
Expr visit(const LE *op, ExprInfo *bounds)
Expr visit(const Call *op, ExprInfo *bounds)
Stmt mutate_let_body(const Stmt &s, ExprInfo *)
Stmt visit(const Acquire *op)
Expr visit(const Broadcast *op, ExprInfo *bounds)
Stmt visit(const Fork *op)
HALIDE_ALWAYS_INLINE bool no_overflow_int(Type t)
Expr visit(const StringImm *op, ExprInfo *bounds)
std::set< Expr, IRDeepCompare > truths
Expr visit(const Select *op, ExprInfo *bounds)
ScopedFact scoped_falsehood(const Expr &fact)
HALIDE_ALWAYS_INLINE bool should_commute(const Expr &a, const Expr &b)
Expr visit(const Or *op, ExprInfo *bounds)
Expr visit(const Mul *op, ExprInfo *bounds)
Expr mutate_let_body(const Expr &e, ExprInfo *bounds)
Stmt visit(const Store *op)
Expr visit(const Mod *op, ExprInfo *bounds)
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
Stmt visit(const Allocate *op)
Stmt visit(const Realize *op)
std::pair< std::vector< Expr >, bool > mutate_with_changes(const std::vector< Expr > &old_exprs, ExprInfo *bounds)
Stmt visit(const LetStmt *op)
std::set< Expr, IRDeepCompare > falsehoods
Expr visit(const EQ *op, ExprInfo *bounds)
Expr visit(const GE *op, ExprInfo *bounds)
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
T mod_imp(T a, T b)
Implementations of division and mod that are specific to Halide.
Definition: IROperator.h:239
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.
HALIDE_MUST_USE_RESULT bool mul_with_overflow(int bits, int64_t a, int64_t b, int64_t *result)
HALIDE_MUST_USE_RESULT bool sub_with_overflow(int bits, int64_t a, int64_t b, int64_t *result)
int64_t saturating_mul(int64_t a, int64_t b)
This file defines the class FunctionDAG, which is our representation of a Halide pipeline,...
Expr min(const FuncRef &a, const FuncRef &b)
Explicit overloads of min and max for FuncRef.
Definition: Func.h:603
Expr max(const FuncRef &a, const FuncRef &b)
Definition: Func.h:606
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:322
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:948
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
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:805
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:932
IRNodeType node_type() const
Definition: Expr.h:212
const T * as() const
Downcast this ir node to its actual type (e.g.
Definition: Expr.h:205
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
Definition: IntrusivePtr.h:168
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:910
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:841
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::vector< const Variable * > pop_list
void learn_lower_bound(const Variable *v, int64_t val)
void learn_upper_bound(const Variable *v, int64_t val)
A reference-counted handle to a statement node.
Definition: Expr.h:419
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:758
std::string name
Definition: IR.h:759
Horizontally reduce a vector to a scalar or narrower vector using the given commutative and associati...
Definition: IR.h:966
Types in the halide type system.
Definition: Type.h:276
HALIDE_ALWAYS_INLINE bool is_int() const
Is this type a signed integer type?
Definition: Type.h:428
HALIDE_ALWAYS_INLINE int bits() const
Return the bit size of a single element of this type.
Definition: Type.h:342
HALIDE_ALWAYS_INLINE bool is_scalar() const
Is this type a scalar type? (lanes() == 1).
Definition: Type.h:410
HALIDE_ALWAYS_INLINE bool is_float() const
Is this type a floating point type (float or double).
Definition: Type.h:416