src/pass/vectorize_loop.cc - tvm - Git at Google

 /*!
  *  Copyright (c) 2017 by Contributors
  * \file vectorize_loop.cc
  */
 // Loop vectorizer as in Halide pipeline.
 #include <tvm/ir.h>
 #include <tvm/ir_pass.h>
 #include <tvm/ir_mutator.h>
 #include <unordered_set>
 #include <unordered_map>
 #include <vector>
 #include "../arithmetic/compute_expr.h"

 namespace tvm {
 namespace ir {

 inline Expr BroadcastTo(Expr e, int lanes) {
   if (e.type().lanes() == lanes) return e;
   if (const Broadcast* op = e.as<Broadcast>()) {
     if (lanes % op->lanes == 0) {
       return Broadcast::make(op->value, lanes);
     }
   }
   CHECK_EQ(e.type().lanes(), 1)
       << "Cannot broadcast lane=" << e.type().lanes()
       << " to " << lanes;
   return Broadcast::make(e, lanes);
 }

 // Rewrite vectorized allocation access
 // This is necessary for making each vector component containing its own workspace.
 // Originates from Halide's loop vectorizer
 //
 // s[i] = s[i * lanes + var]
 //
 // The same principle applies when using one thread to simulate multiple context.
 //
 class VecAllocAccess : public IRMutator {
  public:
   VecAllocAccess(const Variable* buf, Var var, int var_lanes)
       : buf_(buf), var_(var), var_lanes_(var_lanes) {}
   // Load
   Expr Mutate_(const Load* op, const Expr& e) final {
     Expr expr = IRMutator::Mutate_(op, e);
     op = expr.as<Load>();
     if (op->buffer_var.get() == buf_) {
       return Load::make(op->type, op->buffer_var,
                         op->index * var_lanes_ + var_,
                         op->predicate);
     } else {
       return expr;
     }
   }
   // Store
   Stmt Mutate_(const Store* op, const Stmt& s) final {
     Stmt stmt = IRMutator::Mutate_(op, s);
     op = stmt.as<Store>();
     if (op->buffer_var.get() == buf_) {
       return Store::make(op->buffer_var,
                          op->value,
                          op->index * var_lanes_ + var_,
                          op->predicate);
     } else {
       return stmt;
     }
   }

  private:
   // buffer var
   const Variable* buf_;
   // variable to be replaced
   Var var_;
   // the lanes.
   int var_lanes_;
 };

 class Vectorizer : public IRMutator {
  public:
   Vectorizer(Var var, int var_lanes)
       : var_(var), var_lanes_(var_lanes) {
     ramp_ = Ramp::make(0, 1, var_lanes);
   }
   // user mutate from parent.
   using IRMutator::Mutate;

   Stmt Mutate(Stmt stmt) final {
     CHECK(!need_scalarize_);

     Stmt ret = IRMutator::Mutate(stmt);
     if (need_scalarize_) {
       need_scalarize_ = false;
       return Scalarize(stmt);
     } else {
       return ret;
     }
   }


   Expr Mutate_(const Add* op, const Expr &e) final {
     return AddSubVec(op, e);
   }
   Expr Mutate_(const Sub* op, const Expr &e) final {
     return AddSubVec(op, e);
   }
   Expr Mutate_(const Mul* op, const Expr &e) final {
     Expr a = this->Mutate(op->a);
     Expr b = this->Mutate(op->b);
     if (a.same_as(op->a) &&
         b.same_as(op->b)) {
       return e;
     } else {
       int lanes = std::max(a.type().lanes(), b.type().lanes());
       if (lanes != 1) {
         const Ramp* b_ramp = b.as<Ramp>();
         const Ramp* a_ramp = a.as<Ramp>();
         if (a_ramp && b.type().lanes() == 1 && can_prove(b > 0)) {
           return Ramp::make(
               a_ramp->base * b, a_ramp->stride * b, a_ramp->lanes);
         }
         if (b_ramp && a.type().lanes() == 1 && can_prove(a > 0)) {
           return Ramp::make(
               b_ramp->base * a, b_ramp->stride * a, b_ramp->lanes);
         }
       }
       return Mul::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
     }
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Div* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Mod* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Min* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Max* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const EQ* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const NE* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const LT* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const GT* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const GE* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const And* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Or* op, const Expr &e) final {
     return BinaryVec(op, e);
   }
   Expr Mutate_(const Ramp* op, const Expr &e) final {
     Expr base = this->Mutate(op->base);
     Expr stride = this->Mutate(op->stride);
     if (base.type().lanes() > 1 && stride.type().lanes() == 1) {
       const Ramp* base_ramp = base.as<Ramp>();
       if (can_prove(base_ramp->stride == stride * make_const(stride.type(), op->lanes))) {
         return Ramp::make(base_ramp->base, stride, op->lanes * base_ramp->lanes);
       }
     }
     int lanes = std::max(base.type().lanes(), stride.type().lanes());
     base = BroadcastTo(base, lanes);
     stride = BroadcastTo(stride, lanes);
     Array<Expr> elems;
     for (int i = 0; i < lanes; ++i) {
       elems.push_back(
           Ramp::make(Shuffle::make_extract_element(base, i),
                      Shuffle::make_extract_element(stride, i),
                      op->lanes));
     }
     return Shuffle::make_concat(elems);
   }
   Expr Mutate_(const Select *op, const Expr& e) final {
     Expr cond = this->Mutate(op->condition);
     Expr t = this->Mutate(op->true_value);
     Expr f = this->Mutate(op->false_value);
     if (cond.same_as(op->condition) &&
         t.same_as(op->true_value) &&
         f.same_as(op->false_value)) {
       return e;
     } else {
       int lanes = std::max(std::max(
           cond.type().lanes(),
           t.type().lanes()), f.type().lanes());
       return Select::make(cond, BroadcastTo(t, lanes), BroadcastTo(f, lanes));
     }
   }
   Expr Mutate_(const Cast *op, const Expr& e) final {
     Expr value = this->Mutate(op->value);
     if (value.same_as(op->value)) {
       return e;
     } else {
       return Cast::make(op->type.with_lanes(value.type().lanes()), value);
     }
   }
   // Variable
   Expr Mutate_(const Variable* v, const Expr& e) final {
     if (v == var_.get()) {
       return ramp_;
     } else if (lets_.count(v)) {
         return lets_[v];
     } else {
       return e;
     }
   }
   // IfThenElse expr
   Expr MutateIfThenElseExpr_(const Call *op, const Expr& e) {
     Expr cond = this->Mutate(op->args[0]);
     if (cond.type().is_vector())  {
       need_scalarize_ = true;
       return e;
     }
     Expr t = this->Mutate(op->args[1]);
     Expr f = this->Mutate(op->args[2]);
     if (cond.same_as(op->args[0]) &&
         t.same_as(op->args[1]) &&
         f.same_as(op->args[2])) {
       return e;
     } else {
       int lanes = std::max(t.type().lanes(), f.type().lanes());
       t = BroadcastTo(t, lanes);
       f = BroadcastTo(f, lanes);
       return Call::make(
           op->type.with_lanes(lanes), op->name,
           {cond, t, f}, op->call_type, op->func, op->value_index);
     }
   }
   // Call
   Expr Mutate_(const Call* op, const Expr& e) final {
     if (op->name == intrinsic::tvm_if_then_else) {
       return MutateIfThenElseExpr_(op, e);
     }
     int lane = 0;
     Array<Expr> new_args = MutateArray(op->args, &lane);

     // normal code path.
     if (op->args.same_as(new_args)) {
       return e;
     } else {
       return Call::make(
           op->type.with_lanes(lane), op->name, new_args,
           op->call_type, op->func, op->value_index);
     }
   }
   // Load
   Expr Mutate_(const Load* op, const Expr& e) final {
     Expr index = this->Mutate(op->index);
     Expr pred = this->Mutate(op->predicate);
     if (index.same_as(op->index) && pred.same_as(op->predicate)) {
       return e;
     } else {
       int lanes = std::max(index.type().lanes(), pred.type().lanes());
       return Load::make(
           op->type.with_lanes(lanes),
           op->buffer_var,
           BroadcastTo(index, lanes),
           BroadcastTo(pred, lanes));
     }
   }
   // Let
   Expr Mutate_(const Let* op, const Expr& e) final {
     Expr value = this->Mutate(op->value);
     CHECK(!lets_.count(op->var.get())) << "not SSA";
     if (value.type().lanes() != op->value.type().lanes()) {
       Var v(op->var->name_hint, value.type());
       lets_[op->var.get()] = v;
       return Let::make(v, value, Mutate(op->body));
     } else {
       Expr body = this->Mutate(op->body);
       if (value.same_as(op->value) &&
           body.same_as(op->body)) {
         return e;
       } else {
         return Let::make(op->var, value, body);
       }
     }
   }
   // Provide
   Stmt Mutate_(const Provide* op, const Stmt& s) final {
     Expr new_value = this->Mutate(op->value);
     int lane = new_value.type().lanes();
     Array<Expr> new_args = MutateArray(op->args, &lane);
     if (op->args.same_as(new_args) && op->value.same_as(new_value)) {
       return s;
     } else {
       new_value = BroadcastTo(new_value, lane);
       return Provide::make(op->func, op->value_index, new_value, new_args);
     }
   }
   // Store
   Stmt Mutate_(const Store* op, const Stmt& s) final {
     Expr value = this->Mutate(op->value);
     Expr index = this->Mutate(op->index);
     Expr pred = this->Mutate(op->predicate);
     if (value.same_as(op->value) && index.same_as(op->index)) {
       return s;
     } else {
       int lanes = std::max(value.type().lanes(), index.type().lanes());
       lanes = std::max(lanes, pred.type().lanes());
       return Store::make(op->buffer_var,
                          BroadcastTo(value, lanes),
                          BroadcastTo(index, lanes),
                          BroadcastTo(pred, lanes));
     }
   }
   // For
   Stmt Mutate_(const For* op, const Stmt& s) final {
     if (op->for_type == ForType::Vectorized) {
       LOG(WARNING) << "Detect vectorize inside vectorized loop, ignoring...";
     }
     CHECK(is_zero(op->min));
     CHECK(!op->extent.type().is_vector());
     Expr extent = Mutate(op->extent);
     if (extent.type().is_vector()) {
       LOG(WARNING) << "Detect vectorized extent type, scalarizing...";
       return Scalarize(s);
     }
     Stmt body = Mutate(op->body);
     if (extent.same_as(op->extent) &&
         body.same_as(op->body)) {
       return s;
     } else {
       return For::make(
           op->loop_var, op->min, extent,
           op->for_type, op->device_api, body);
     }
   }
   // IfThenElse
   Stmt Mutate_(const IfThenElse* op, const Stmt& s) final {
     CHECK(!op->condition.type().is_vector());
     Expr condition = this->Mutate(op->condition);
     if (condition.type().is_vector()) {
       LOG(WARNING) << "Detect vector condition in Vectorized Loop, scalarizing...";
       return Scalarize(s);
     }
     Stmt then_case = this->Mutate(op->then_case);
     Stmt else_case;
     if (op->else_case.defined()) {
       else_case = this->Mutate(op->else_case);
     }
     if (condition.same_as(op->condition) &&
         then_case.same_as(op->then_case) &&
         else_case.same_as(op->else_case)) {
       return s;
     } else {
       return IfThenElse::make(condition, then_case, else_case);
     }
   }
   // LetStmt
   Stmt Mutate_(const LetStmt* op, const Stmt& s) final {
     LOG(WARNING) << "Cannot vectorize with LetStmt, remove it with Simplify Before Vectorize";
     return Scalarize(s);
   }
   // Allocate
   Stmt Mutate_(const Allocate* op, const Stmt& s) final {
     if (op->new_expr.defined()) {
       LOG(WARNING) << "Cannot vectorize with new expr";
       return Scalarize(s);
     }
     Expr condition = Mutate(op->condition);
     if (condition.type().is_vector()) {
       LOG(WARNING) << "Cannot handle vector extent in alloc ";
       return Scalarize(s);
     }
     Array<Expr> extents;
     for (size_t i = 0; i < op->extents.size(); i++) {
       Expr new_ext = Mutate(op->extents[i]);
       if (new_ext.type().is_vector()) {
         LOG(WARNING) << "Cannot handle vector extent in alloc ";
         return Scalarize(s);
       }
       extents.push_back(new_ext);
     }
     // place the vector lanes in least significant dimension.
     extents.push_back(var_lanes_);
     // rewrite access to buffer internally.
     Stmt body = VecAllocAccess(
         op->buffer_var.get(), var_, var_lanes_).Mutate(op->body);
     body = Mutate(body);
     return Allocate::make(
         op->buffer_var, op->type,
         extents, condition, body,
         op->new_expr, op->free_function);
   }
   // scalarize the statment
   Stmt Scalarize(Stmt stmt) {
     Var idx(var_->name_hint + ".s", var_->type);
     Map<Var, Expr> values{{var_, idx}};
     stmt = Substitute(stmt, values);
     return For::make(idx, 0, var_lanes_, ForType::Serial, DeviceAPI::None, stmt);
   }

  private:
   // variable to be replaced
   Var var_;
   // the lanes.
   int var_lanes_;
   // ramp representing the var.
   Expr ramp_;
   // flag to mark requirment of scalarization.
   bool need_scalarize_{false};
   // The lets
   std::unordered_map<const Variable*, Expr> lets_;
   // mutate array, with given lane requirement
   // when finished, p_lane updates the lane requirement.
   Array<Expr> MutateArray(Array<Expr> arr, int* p_lanes) {
     if (arr.size() == 0) return arr;
     int& lanes = *p_lanes;
     bool changed = false;
     std::vector<Expr> new_arr(arr.size());
     for (size_t i = 0; i < arr.size(); i++) {
       Expr old_elem = arr[i];
       Expr new_elem = this->Mutate(old_elem);
       if (!new_elem.same_as(old_elem)) changed = true;
       new_arr[i] = new_elem;
       lanes = std::max(lanes, new_elem.type().lanes());
     }

     for (size_t i = 0; i < arr.size(); ++i) {
       if (new_arr[i].type().lanes() != lanes) {
         new_arr[i] = BroadcastTo(new_arr[i], lanes);
         changed = true;
       }
     }
     if (!changed) return arr;
     return Array<Expr>(new_arr);
   }
   template<typename T>
   Expr BinaryVec(const T* op, const Expr& e) {
     Expr a = this->Mutate(op->a);
     Expr b = this->Mutate(op->b);
     if (a.same_as(op->a) &&
         b.same_as(op->b)) {
       return e;
     } else {
       int lanes = std::max(a.type().lanes(), b.type().lanes());
       return T::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
     }
   }
   template<typename T>
   Expr AddSubVec(const T* op, const Expr& e) {
     Expr a = this->Mutate(op->a);
     Expr b = this->Mutate(op->b);
     if (a.same_as(op->a) &&
         b.same_as(op->b)) {
       return e;
     } else {
       int lanes = std::max(a.type().lanes(), b.type().lanes());
       if (lanes != 1) {
         const Ramp* b_ramp = b.as<Ramp>();
         const Ramp* a_ramp = a.as<Ramp>();
         if (a.type().lanes() == 1 && b_ramp) {
           return Ramp::make(
               arith::ComputeExpr<T>(a, b_ramp->base),
               arith::ComputeExpr<T>(make_zero(b_ramp->stride.type()), b_ramp->stride),
               b_ramp->lanes);
         }
         if (b.type().lanes() == 1 && a_ramp) {
           return Ramp::make(
               arith::ComputeExpr<T>(a_ramp->base, b), a_ramp->stride, a_ramp->lanes);
         }
       }
       return T::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
     }
   }
 };

 class LoopVectorizer : public IRMutator {
  public:
   Stmt Mutate_(const For* op, const Stmt& s) final {
     if (op->for_type == ForType::Vectorized) {
       CHECK(is_zero(op->min));
       int lanes = 0;
       bool succ = arith::GetConstInt(op->extent, &lanes);
       if (!succ || lanes < 1) {
         LOG(FATAL) << "Failed to vectorize loop with extent " << op->extent;
       }
       Var var(op->loop_var.node_);
       return Vectorizer(var, lanes).Mutate(op->body);
     } else {
       return IRMutator::Mutate_(op, s);
     }
   }
 };

 Stmt VectorizeLoop(Stmt stmt) {
   return LoopVectorizer().Mutate(stmt);
 }

 }  // namespace ir
 }  // namespace tvm
	/*!
	* Copyright (c) 2017 by Contributors
	* \file vectorize_loop.cc
	*/
	// Loop vectorizer as in Halide pipeline.
	#include <tvm/ir.h>
	#include <tvm/ir_pass.h>
	#include <tvm/ir_mutator.h>
	#include <unordered_set>
	#include <unordered_map>
	#include <vector>
	#include "../arithmetic/compute_expr.h"

	namespace tvm {
	namespace ir {

	inline Expr BroadcastTo(Expr e, int lanes) {
	if (e.type().lanes() == lanes) return e;
	if (const Broadcast* op = e.as<Broadcast>()) {
	if (lanes % op->lanes == 0) {
	return Broadcast::make(op->value, lanes);
	}
	}
	CHECK_EQ(e.type().lanes(), 1)
	<< "Cannot broadcast lane=" << e.type().lanes()
	<< " to " << lanes;
	return Broadcast::make(e, lanes);
	}

	// Rewrite vectorized allocation access
	// This is necessary for making each vector component containing its own workspace.
	// Originates from Halide's loop vectorizer
	//
	// s[i] = s[i * lanes + var]
	//
	// The same principle applies when using one thread to simulate multiple context.
	//
	class VecAllocAccess : public IRMutator {
	public:
	VecAllocAccess(const Variable* buf, Var var, int var_lanes)
	: buf_(buf), var_(var), var_lanes_(var_lanes) {}
	// Load
	Expr Mutate_(const Load* op, const Expr& e) final {
	Expr expr = IRMutator::Mutate_(op, e);
	op = expr.as<Load>();
	if (op->buffer_var.get() == buf_) {
	return Load::make(op->type, op->buffer_var,
	op->index * var_lanes_ + var_,
	op->predicate);
	} else {
	return expr;
	}
	}
	// Store
	Stmt Mutate_(const Store* op, const Stmt& s) final {
	Stmt stmt = IRMutator::Mutate_(op, s);
	op = stmt.as<Store>();
	if (op->buffer_var.get() == buf_) {
	return Store::make(op->buffer_var,
	op->value,
	op->index * var_lanes_ + var_,
	op->predicate);
	} else {
	return stmt;
	}
	}

	private:
	// buffer var
	const Variable* buf_;
	// variable to be replaced
	Var var_;
	// the lanes.
	int var_lanes_;
	};

	class Vectorizer : public IRMutator {
	public:
	Vectorizer(Var var, int var_lanes)
	: var_(var), var_lanes_(var_lanes) {
	ramp_ = Ramp::make(0, 1, var_lanes);
	}
	// user mutate from parent.
	using IRMutator::Mutate;

	Stmt Mutate(Stmt stmt) final {
	CHECK(!need_scalarize_);

	Stmt ret = IRMutator::Mutate(stmt);
	if (need_scalarize_) {
	need_scalarize_ = false;
	return Scalarize(stmt);
	} else {
	return ret;
	}
	}


	Expr Mutate_(const Add* op, const Expr &e) final {
	return AddSubVec(op, e);
	}
	Expr Mutate_(const Sub* op, const Expr &e) final {
	return AddSubVec(op, e);
	}
	Expr Mutate_(const Mul* op, const Expr &e) final {
	Expr a = this->Mutate(op->a);
	Expr b = this->Mutate(op->b);
	if (a.same_as(op->a) &&
	b.same_as(op->b)) {
	return e;
	} else {
	int lanes = std::max(a.type().lanes(), b.type().lanes());
	if (lanes != 1) {
	const Ramp* b_ramp = b.as<Ramp>();
	const Ramp* a_ramp = a.as<Ramp>();
	if (a_ramp && b.type().lanes() == 1 && can_prove(b > 0)) {
	return Ramp::make(
	a_ramp->base * b, a_ramp->stride * b, a_ramp->lanes);
	}
	if (b_ramp && a.type().lanes() == 1 && can_prove(a > 0)) {
	return Ramp::make(
	b_ramp->base * a, b_ramp->stride * a, b_ramp->lanes);
	}
	}
	return Mul::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
	}
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Div* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Mod* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Min* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Max* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const EQ* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const NE* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const LT* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const GT* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const GE* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const And* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Or* op, const Expr &e) final {
	return BinaryVec(op, e);
	}
	Expr Mutate_(const Ramp* op, const Expr &e) final {
	Expr base = this->Mutate(op->base);
	Expr stride = this->Mutate(op->stride);
	if (base.type().lanes() > 1 && stride.type().lanes() == 1) {
	const Ramp* base_ramp = base.as<Ramp>();
	if (can_prove(base_ramp->stride == stride * make_const(stride.type(), op->lanes))) {
	return Ramp::make(base_ramp->base, stride, op->lanes * base_ramp->lanes);
	}
	}
	int lanes = std::max(base.type().lanes(), stride.type().lanes());
	base = BroadcastTo(base, lanes);
	stride = BroadcastTo(stride, lanes);
	Array<Expr> elems;
	for (int i = 0; i < lanes; ++i) {
	elems.push_back(
	Ramp::make(Shuffle::make_extract_element(base, i),
	Shuffle::make_extract_element(stride, i),
	op->lanes));
	}
	return Shuffle::make_concat(elems);
	}
	Expr Mutate_(const Select *op, const Expr& e) final {
	Expr cond = this->Mutate(op->condition);
	Expr t = this->Mutate(op->true_value);
	Expr f = this->Mutate(op->false_value);
	if (cond.same_as(op->condition) &&
	t.same_as(op->true_value) &&
	f.same_as(op->false_value)) {
	return e;
	} else {
	int lanes = std::max(std::max(
	cond.type().lanes(),
	t.type().lanes()), f.type().lanes());
	return Select::make(cond, BroadcastTo(t, lanes), BroadcastTo(f, lanes));
	}
	}
	Expr Mutate_(const Cast *op, const Expr& e) final {
	Expr value = this->Mutate(op->value);
	if (value.same_as(op->value)) {
	return e;
	} else {
	return Cast::make(op->type.with_lanes(value.type().lanes()), value);
	}
	}
	// Variable
	Expr Mutate_(const Variable* v, const Expr& e) final {
	if (v == var_.get()) {
	return ramp_;
	} else if (lets_.count(v)) {
	return lets_[v];
	} else {
	return e;
	}
	}
	// IfThenElse expr
	Expr MutateIfThenElseExpr_(const Call *op, const Expr& e) {
	Expr cond = this->Mutate(op->args[0]);
	if (cond.type().is_vector()) {
	need_scalarize_ = true;
	return e;
	}
	Expr t = this->Mutate(op->args[1]);
	Expr f = this->Mutate(op->args[2]);
	if (cond.same_as(op->args[0]) &&
	t.same_as(op->args[1]) &&
	f.same_as(op->args[2])) {
	return e;
	} else {
	int lanes = std::max(t.type().lanes(), f.type().lanes());
	t = BroadcastTo(t, lanes);
	f = BroadcastTo(f, lanes);
	return Call::make(
	op->type.with_lanes(lanes), op->name,
	{cond, t, f}, op->call_type, op->func, op->value_index);
	}
	}
	// Call
	Expr Mutate_(const Call* op, const Expr& e) final {
	if (op->name == intrinsic::tvm_if_then_else) {
	return MutateIfThenElseExpr_(op, e);
	}
	int lane = 0;
	Array<Expr> new_args = MutateArray(op->args, &lane);

	// normal code path.
	if (op->args.same_as(new_args)) {
	return e;
	} else {
	return Call::make(
	op->type.with_lanes(lane), op->name, new_args,
	op->call_type, op->func, op->value_index);
	}
	}
	// Load
	Expr Mutate_(const Load* op, const Expr& e) final {
	Expr index = this->Mutate(op->index);
	Expr pred = this->Mutate(op->predicate);
	if (index.same_as(op->index) && pred.same_as(op->predicate)) {
	return e;
	} else {
	int lanes = std::max(index.type().lanes(), pred.type().lanes());
	return Load::make(
	op->type.with_lanes(lanes),
	op->buffer_var,
	BroadcastTo(index, lanes),
	BroadcastTo(pred, lanes));
	}
	}
	// Let
	Expr Mutate_(const Let* op, const Expr& e) final {
	Expr value = this->Mutate(op->value);
	CHECK(!lets_.count(op->var.get())) << "not SSA";
	if (value.type().lanes() != op->value.type().lanes()) {
	Var v(op->var->name_hint, value.type());
	lets_[op->var.get()] = v;
	return Let::make(v, value, Mutate(op->body));
	} else {
	Expr body = this->Mutate(op->body);
	if (value.same_as(op->value) &&
	body.same_as(op->body)) {
	return e;
	} else {
	return Let::make(op->var, value, body);
	}
	}
	}
	// Provide
	Stmt Mutate_(const Provide* op, const Stmt& s) final {
	Expr new_value = this->Mutate(op->value);
	int lane = new_value.type().lanes();
	Array<Expr> new_args = MutateArray(op->args, &lane);
	if (op->args.same_as(new_args) && op->value.same_as(new_value)) {
	return s;
	} else {
	new_value = BroadcastTo(new_value, lane);
	return Provide::make(op->func, op->value_index, new_value, new_args);
	}
	}
	// Store
	Stmt Mutate_(const Store* op, const Stmt& s) final {
	Expr value = this->Mutate(op->value);
	Expr index = this->Mutate(op->index);
	Expr pred = this->Mutate(op->predicate);
	if (value.same_as(op->value) && index.same_as(op->index)) {
	return s;
	} else {
	int lanes = std::max(value.type().lanes(), index.type().lanes());
	lanes = std::max(lanes, pred.type().lanes());
	return Store::make(op->buffer_var,
	BroadcastTo(value, lanes),
	BroadcastTo(index, lanes),
	BroadcastTo(pred, lanes));
	}
	}
	// For
	Stmt Mutate_(const For* op, const Stmt& s) final {
	if (op->for_type == ForType::Vectorized) {
	LOG(WARNING) << "Detect vectorize inside vectorized loop, ignoring...";
	}
	CHECK(is_zero(op->min));
	CHECK(!op->extent.type().is_vector());
	Expr extent = Mutate(op->extent);
	if (extent.type().is_vector()) {
	LOG(WARNING) << "Detect vectorized extent type, scalarizing...";
	return Scalarize(s);
	}
	Stmt body = Mutate(op->body);
	if (extent.same_as(op->extent) &&
	body.same_as(op->body)) {
	return s;
	} else {
	return For::make(
	op->loop_var, op->min, extent,
	op->for_type, op->device_api, body);
	}
	}
	// IfThenElse
	Stmt Mutate_(const IfThenElse* op, const Stmt& s) final {
	CHECK(!op->condition.type().is_vector());
	Expr condition = this->Mutate(op->condition);
	if (condition.type().is_vector()) {
	LOG(WARNING) << "Detect vector condition in Vectorized Loop, scalarizing...";
	return Scalarize(s);
	}
	Stmt then_case = this->Mutate(op->then_case);
	Stmt else_case;
	if (op->else_case.defined()) {
	else_case = this->Mutate(op->else_case);
	}
	if (condition.same_as(op->condition) &&
	then_case.same_as(op->then_case) &&
	else_case.same_as(op->else_case)) {
	return s;
	} else {
	return IfThenElse::make(condition, then_case, else_case);
	}
	}
	// LetStmt
	Stmt Mutate_(const LetStmt* op, const Stmt& s) final {
	LOG(WARNING) << "Cannot vectorize with LetStmt, remove it with Simplify Before Vectorize";
	return Scalarize(s);
	}
	// Allocate
	Stmt Mutate_(const Allocate* op, const Stmt& s) final {
	if (op->new_expr.defined()) {
	LOG(WARNING) << "Cannot vectorize with new expr";
	return Scalarize(s);
	}
	Expr condition = Mutate(op->condition);
	if (condition.type().is_vector()) {
	LOG(WARNING) << "Cannot handle vector extent in alloc ";
	return Scalarize(s);
	}
	Array<Expr> extents;
	for (size_t i = 0; i < op->extents.size(); i++) {
	Expr new_ext = Mutate(op->extents[i]);
	if (new_ext.type().is_vector()) {
	LOG(WARNING) << "Cannot handle vector extent in alloc ";
	return Scalarize(s);
	}
	extents.push_back(new_ext);
	}
	// place the vector lanes in least significant dimension.
	extents.push_back(var_lanes_);
	// rewrite access to buffer internally.
	Stmt body = VecAllocAccess(
	op->buffer_var.get(), var_, var_lanes_).Mutate(op->body);
	body = Mutate(body);
	return Allocate::make(
	op->buffer_var, op->type,
	extents, condition, body,
	op->new_expr, op->free_function);
	}
	// scalarize the statment
	Stmt Scalarize(Stmt stmt) {
	Var idx(var_->name_hint + ".s", var_->type);
	Map<Var, Expr> values{{var_, idx}};
	stmt = Substitute(stmt, values);
	return For::make(idx, 0, var_lanes_, ForType::Serial, DeviceAPI::None, stmt);
	}

	private:
	// variable to be replaced
	Var var_;
	// the lanes.
	int var_lanes_;
	// ramp representing the var.
	Expr ramp_;
	// flag to mark requirment of scalarization.
	bool need_scalarize_{false};
	// The lets
	std::unordered_map<const Variable*, Expr> lets_;
	// mutate array, with given lane requirement
	// when finished, p_lane updates the lane requirement.
	Array<Expr> MutateArray(Array<Expr> arr, int* p_lanes) {
	if (arr.size() == 0) return arr;
	int& lanes = *p_lanes;
	bool changed = false;
	std::vector<Expr> new_arr(arr.size());
	for (size_t i = 0; i < arr.size(); i++) {
	Expr old_elem = arr[i];
	Expr new_elem = this->Mutate(old_elem);
	if (!new_elem.same_as(old_elem)) changed = true;
	new_arr[i] = new_elem;
	lanes = std::max(lanes, new_elem.type().lanes());
	}

	for (size_t i = 0; i < arr.size(); ++i) {
	if (new_arr[i].type().lanes() != lanes) {
	new_arr[i] = BroadcastTo(new_arr[i], lanes);
	changed = true;
	}
	}
	if (!changed) return arr;
	return Array<Expr>(new_arr);
	}
	template<typename T>
	Expr BinaryVec(const T* op, const Expr& e) {
	Expr a = this->Mutate(op->a);
	Expr b = this->Mutate(op->b);
	if (a.same_as(op->a) &&
	b.same_as(op->b)) {
	return e;
	} else {
	int lanes = std::max(a.type().lanes(), b.type().lanes());
	return T::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
	}
	}
	template<typename T>
	Expr AddSubVec(const T* op, const Expr& e) {
	Expr a = this->Mutate(op->a);
	Expr b = this->Mutate(op->b);
	if (a.same_as(op->a) &&
	b.same_as(op->b)) {
	return e;
	} else {
	int lanes = std::max(a.type().lanes(), b.type().lanes());
	if (lanes != 1) {
	const Ramp* b_ramp = b.as<Ramp>();
	const Ramp* a_ramp = a.as<Ramp>();
	if (a.type().lanes() == 1 && b_ramp) {
	return Ramp::make(
	arith::ComputeExpr<T>(a, b_ramp->base),
	arith::ComputeExpr<T>(make_zero(b_ramp->stride.type()), b_ramp->stride),
	b_ramp->lanes);
	}
	if (b.type().lanes() == 1 && a_ramp) {
	return Ramp::make(
	arith::ComputeExpr<T>(a_ramp->base, b), a_ramp->stride, a_ramp->lanes);
	}
	}
	return T::make(BroadcastTo(a, lanes), BroadcastTo(b, lanes));
	}
	}
	};

	class LoopVectorizer : public IRMutator {
	public:
	Stmt Mutate_(const For* op, const Stmt& s) final {
	if (op->for_type == ForType::Vectorized) {
	CHECK(is_zero(op->min));
	int lanes = 0;
	bool succ = arith::GetConstInt(op->extent, &lanes);
	if (!succ \|\| lanes < 1) {
	LOG(FATAL) << "Failed to vectorize loop with extent " << op->extent;
	}
	Var var(op->loop_var.node_);
	return Vectorizer(var, lanes).Mutate(op->body);
	} else {
	return IRMutator::Mutate_(op, s);
	}
	}
	};

	Stmt VectorizeLoop(Stmt stmt) {
	return LoopVectorizer().Mutate(stmt);
	}

	} // namespace ir
	} // namespace tvm