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#include <torch/csrc/jit/tensorexpr/bounds_inference.h>
#include <torch/csrc/jit/tensorexpr/expr.h>
#include <torch/csrc/jit/tensorexpr/ir.h>
#include <torch/csrc/jit/tensorexpr/ir_printer.h>
#include <torch/csrc/jit/tensorexpr/ir_simplifier.h>
#include <torch/csrc/jit/tensorexpr/ir_visitor.h>
#include <torch/csrc/jit/tensorexpr/stmt.h>
namespace torch {
namespace jit {
namespace tensorexpr {
class BoundsInference : public IRVisitor {
public:
void visit(const FunctionCall* v) override;
void visit(const Load* v) override;
void visit(const Store* v) override;
void visit(const For* v) override;
void visit(const Block* v) override;
BoundsInfo accesses() const {
return accesses_;
}
private:
BoundsInfo accesses_;
};
void BoundsInference::visit(const Load* v) {
accesses_[v->buf()].push_back({kLoad, v->indices(), v->indices()});
}
void BoundsInference::visit(const FunctionCall* v) {
accesses_[v->tensor()->buf()].push_back({kLoad, v->params(), v->params()});
}
void BoundsInference::visit(const Store* v) {
accesses_[v->buf()].push_back({kStore, v->indices(), v->indices()});
IRVisitor::visit(v);
}
void BoundsInference::visit(const For* v) {
v->body()->accept(this);
for (auto& pair : accesses_) {
for (TensorAccessBoundsInfo& access : pair.second) {
for (size_t j = 0; j < access.start.size(); j++) {
// TODO: This function assumes that all indices grow monotonically and
// thus for the loop:
// for i in A..B:
// buf[i] = i
// the range for i is [A, B). It should be generalized to correctly
// handle all cases.
const Expr* old_start = access.start[j];
const Expr* old_stop = access.stop[j];
const Expr* new_start = Substitute(old_start, {{v->var(), v->start()}});
const Expr* new_stop = Substitute(
old_stop, {{v->var(), new Sub(v->stop(), new IntImm(1))}});
access.start[j] = IRSimplifier::simplify(new_start);
access.stop[j] = IRSimplifier::simplify(new_stop);
}
}
}
}
void BoundsInference::visit(const Block* v) {
BoundsInfo res;
for (auto s : *v) {
s->accept(this);
for (auto& pair : accesses_) {
res[pair.first].insert(
res[pair.first].end(), pair.second.begin(), pair.second.end());
}
}
accesses_ = res;
}
void printBoundsInfo(const BoundsInfo& v) {
std::cerr << "Access vector {\n";
for (auto& pair : v) {
std::cerr << *pair.first << " in [";
bool first = true;
for (const auto& b : pair.second) {
if (!first) {
std::cerr << ", ";
}
std::cerr << ((b.kind == kLoad) ? "LOAD" : "STORE") << "(";
int i = 0;
if (b.start.empty()) {
std::cerr << "0";
}
for (const auto& s : b.start) {
if (i != 0) {
std::cerr << ", ";
}
std::cerr << *s;
i++;
}
std::cerr << "; ";
i = 0;
if (b.stop.empty()) {
std::cerr << "0";
}
for (const auto& s : b.stop) {
if (i != 0) {
std::cerr << ", ";
}
std::cerr << *s;
i++;
}
std::cerr << ")";
first = false;
}
std::cerr << "]\n";
}
std::cerr << "}\n";
}
bool equalExprs(const Expr* A, const Expr* B) {
const Expr* diff = IRSimplifier::simplify(new Sub(B, A));
return diff->isConstant() && immediateEquals(diff, 0);
}
// returns the bounds of an overlapping range, or {nullptr, nullptr} if the
// ranges don't overlap.
std::pair<const Expr*, const Expr*> rangeOverlap(
const Expr* s1,
const Expr* e1,
const Expr* s2,
const Expr* e2) {
// If they're equal they're equal.
if (equalExprs(s1, s2) && equalExprs(e1, e2)) {
return {s1, e1};
}
std::pair<const Expr*, const Expr*> noOverlap = {nullptr, nullptr};
std::pair<const Expr*, const Expr*> overlap = {
IRSimplifier::simplify(new Min(s1, s2, true)),
IRSimplifier::simplify(new Max(e1, e2, true))};
const Expr* lowDiff = IRSimplifier::simplify(new Sub(s1, e2));
const Expr* highDiff = IRSimplifier::simplify(new Sub(s2, e1));
if (lowDiff->isConstant() && highDiff->isConstant()) {
// No overlap.
if (!(immediateAs<int>(lowDiff) <= 1 || immediateAs<int>(highDiff) >= 1)) {
return noOverlap;
}
return overlap;
}
// Can still merge if we can infer adjacency without knowing static values:
// If we know one side, we can use the fact that each eX >= sX.
if (highDiff->isConstant() && abs(immediateAs<int>(highDiff)) <= 1) {
return {s1, e2};
}
if (lowDiff->isConstant() && abs(immediateAs<int>(lowDiff)) <= 1) {
return {s2, e1};
}
const Expr* diffs = IRSimplifier::simplify(new Sub(s2, s1));
const Expr* diffe = IRSimplifier::simplify(new Sub(e2, e1));
// If one side fully encloses the other, they're adjacent.
if (diffs->isConstant() && diffe->isConstant()) {
int ds_i = immediateAs<int>(diffs);
int de_i = immediateAs<int>(diffe);
if ((ds_i <= 0 && de_i >= 0) || (ds_i >= 0 && de_i <= 0)) {
return overlap;
}
}
// If either the start or end is 1 element apart from it's pair, they must
// be adjacent.
if (diffs->isConstant() && abs(immediateAs<int>(diffs)) <= 1) {
return overlap;
}
if (diffe->isConstant() && abs(immediateAs<int>(diffe)) <= 1) {
return overlap;
}
return noOverlap;
}
/*
* Go through the given BoundsInfo vector and merge entries corresponding to
* the same buf. E.g. given
* [{a, kLoad, 0, 100}, {b, kStore, 0, 100}, {a, kLoad, 10, 110}]
* produce:
* [{a, kLoad, 0, 110}, {b, kStore, 0, 100}]
*/
BoundsInfo mergeTensorAccesses(const BoundsInfo& unmerged) {
BoundsInfo res;
// For each buf in the BoundsInfo:
for (auto& pair : unmerged) {
const std::vector<TensorAccessBoundsInfo>& new_vec = pair.second;
std::vector<TensorAccessBoundsInfo>& existing_vec = res[pair.first];
// For each bound pair in the unmerged set:
for (const auto& new_bound : new_vec) {
bool found = false;
// For each already merged bound pair:
for (auto& existing_bound : existing_vec) {
// Only merge the same kind of access.
if (existing_bound.kind != new_bound.kind) {
continue;
}
// Sanity check the buf indices have the same dimensionality.
TORCH_INTERNAL_ASSERT(new_bound.start.size() == new_bound.stop.size());
TORCH_INTERNAL_ASSERT(
existing_bound.start.size() == existing_bound.stop.size());
TORCH_INTERNAL_ASSERT(
new_bound.start.size() == existing_bound.start.size());
std::vector<const Expr*> start;
std::vector<const Expr*> stop;
bool fail = false;
// For each dimension:
for (size_t i = 0; i < new_bound.start.size(); ++i) {
// The range of the new bound must overlap the existing bound.
// TODO(nickg): we allow all dimensions to partially overlap,
// which will overstate the bounds.
auto pair = rangeOverlap(
new_bound.start[i],
new_bound.stop[i],
existing_bound.start[i],
existing_bound.stop[i]);
if (pair.first == nullptr) {
fail = true;
break;
}
start.push_back(pair.first);
stop.push_back(pair.second);
}
if (fail) {
continue;
}
found = true;
// Update the existing bound.
existing_bound.start = start;
existing_bound.stop = stop;
}
if (!found) {
existing_vec.push_back(new_bound);
}
}
}
return res;
}
BoundsInfo inferBounds(Stmt* s) {
BoundsInference ac;
s->accept(&ac);
return mergeTensorAccesses(ac.accesses());
}
} // namespace tensorexpr
} // namespace jit
} // namespace torch
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