This patch to the Go frontend by Cherry Zhang recognizes and optimizes
array range clear. It looks for
for i := range a { a[i] = zero }
for array or slice a, and rewrites it to call memclr, as the gc compiler does.
Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed
to mainline.
Ian
Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE (revision 270857)
+++ gcc/go/gofrontend/MERGE (working copy)
@@ -1,4 +1,4 @@
-208521930c9b5adcfb495799ee01b6aec86c2ccf
+4b3015de639cf22ed11ff96097555700909827c8
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.
Index: gcc/go/gofrontend/expressions.cc
===================================================================
--- gcc/go/gofrontend/expressions.cc (revision 270779)
+++ gcc/go/gofrontend/expressions.cc (working copy)
@@ -1672,6 +1672,10 @@ class Boolean_expression : public Expres
{ return true; }
bool
+ do_is_zero_value() const
+ { return this->val_ == false; }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -2055,6 +2059,10 @@ class Integer_expression : public Expres
{ return true; }
bool
+ do_is_zero_value() const
+ { return mpz_sgn(this->val_) == 0; }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -2475,6 +2483,13 @@ class Float_expression : public Expressi
{ return true; }
bool
+ do_is_zero_value() const
+ {
+ return mpfr_zero_p(this->val_) != 0
+ && mpfr_signbit(this->val_) == 0;
+ }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -2686,6 +2701,15 @@ class Complex_expression : public Expres
{ return true; }
bool
+ do_is_zero_value() const
+ {
+ return mpfr_zero_p(mpc_realref(this->val_)) != 0
+ && mpfr_signbit(mpc_realref(this->val_)) == 0
+ && mpfr_zero_p(mpc_imagref(this->val_)) != 0
+ && mpfr_signbit(mpc_imagref(this->val_)) == 0;
+ }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -2923,6 +2947,10 @@ class Const_expression : public Expressi
{ return true; }
bool
+ do_is_zero_value() const
+ { return this->constant_->const_value()->expr()->is_zero_value(); }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -3290,6 +3318,10 @@ class Nil_expression : public Expression
{ return true; }
bool
+ do_is_zero_value() const
+ { return true; }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -3533,6 +3565,28 @@ Type_conversion_expression::do_is_consta
return true;
}
+// Return whether a type conversion is a zero value.
+
+bool
+Type_conversion_expression::do_is_zero_value() const
+{
+ if (!this->expr_->is_zero_value())
+ return false;
+
+ // Some type conversion from zero value is still not zero value.
+ // For example, []byte("") or interface{}(0).
+ // Conservatively, only report true if the RHS is nil.
+ Type* type = this->type_;
+ if (type->integer_type() == NULL
+ && type->float_type() == NULL
+ && type->complex_type() == NULL
+ && !type->is_boolean_type()
+ && !type->is_string_type())
+ return this->expr_->is_nil_expression();
+
+ return true;
+}
+
// Return whether a type conversion can be used in a constant
// initializer.
@@ -6880,6 +6934,19 @@ String_concat_expression::do_is_constant
}
bool
+String_concat_expression::do_is_zero_value() const
+{
+ for (Expression_list::const_iterator pe = this->exprs_->begin();
+ pe != this->exprs_->end();
+ ++pe)
+ {
+ if (!(*pe)->is_zero_value())
+ return false;
+ }
+ return true;
+}
+
+bool
String_concat_expression::do_is_static_initializer() const
{
for (Expression_list::const_iterator pe = this->exprs_->begin();
@@ -13007,6 +13074,33 @@ Struct_construction_expression::is_const
return true;
}
+// Return whether this is a zero value.
+
+bool
+Struct_construction_expression::do_is_zero_value() const
+{
+ if (this->vals() == NULL)
+ return true;
+ for (Expression_list::const_iterator pv = this->vals()->begin();
+ pv != this->vals()->end();
+ ++pv)
+ if (*pv != NULL && !(*pv)->is_zero_value())
+ return false;
+
+ const Struct_field_list* fields = this->type_->struct_type()->fields();
+ for (Struct_field_list::const_iterator pf = fields->begin();
+ pf != fields->end();
+ ++pf)
+ {
+ // Interface conversion may cause a zero value being converted
+ // to a non-zero value, like interface{}(0). Be conservative.
+ if (pf->type()->interface_type() != NULL)
+ return false;
+ }
+
+ return true;
+}
+
// Return whether this struct can be used as a constant initializer.
bool
@@ -13288,6 +13382,28 @@ Array_construction_expression::is_consta
return true;
}
+// Return whether this is a zero value.
+
+bool
+Array_construction_expression::do_is_zero_value() const
+{
+ if (this->vals() == NULL)
+ return true;
+
+ // Interface conversion may cause a zero value being converted
+ // to a non-zero value, like interface{}(0). Be conservative.
+ if (this->type_->array_type()->element_type()->interface_type() != NULL)
+ return false;
+
+ for (Expression_list::const_iterator pv = this->vals()->begin();
+ pv != this->vals()->end();
+ ++pv)
+ if (*pv != NULL && !(*pv)->is_zero_value())
+ return false;
+
+ return true;
+}
+
// Return whether this can be used a constant initializer.
bool
Index: gcc/go/gofrontend/expressions.h
===================================================================
--- gcc/go/gofrontend/expressions.h (revision 270779)
+++ gcc/go/gofrontend/expressions.h (working copy)
@@ -544,6 +544,11 @@ class Expression
is_constant() const
{ return this->do_is_constant(); }
+ // Return whether this is the zero value of its type.
+ bool
+ is_zero_value() const
+ { return this->do_is_zero_value(); }
+
// Return whether this expression can be used as a static
// initializer. This is true for an expression that has only
// numbers and pointers to global variables or composite literals
@@ -1066,6 +1071,11 @@ class Expression
do_is_constant() const
{ return false; }
+ // Return whether this is the zero value of its type.
+ virtual bool
+ do_is_zero_value() const
+ { return false; }
+
// Return whether this expression can be used as a constant
// initializer.
virtual bool
@@ -1600,6 +1610,10 @@ class String_expression : public Express
{ return true; }
bool
+ do_is_zero_value() const
+ { return this->val_ == ""; }
+
+ bool
do_is_static_initializer() const
{ return true; }
@@ -1693,6 +1707,9 @@ class Type_conversion_expression : publi
do_is_constant() const;
bool
+ do_is_zero_value() const;
+
+ bool
do_is_static_initializer() const;
bool
@@ -1756,6 +1773,10 @@ class Unsafe_type_conversion_expression
do_traverse(Traverse* traverse);
bool
+ do_is_zero_value() const
+ { return this->expr_->is_zero_value(); }
+
+ bool
do_is_static_initializer() const;
Type*
@@ -2152,6 +2173,9 @@ class String_concat_expression : public
do_is_constant() const;
bool
+ do_is_zero_value() const;
+
+ bool
do_is_static_initializer() const;
Type*
@@ -3570,7 +3594,7 @@ class Struct_construction_expression : p
type_(type)
{ }
- // Return whether this is a constant initializer.
+ // Return whether this is a constant initializer.
bool
is_constant_struct() const;
@@ -3579,6 +3603,9 @@ class Struct_construction_expression : p
do_traverse(Traverse* traverse);
bool
+ do_is_zero_value() const;
+
+ bool
do_is_static_initializer() const;
Type*
@@ -3643,6 +3670,9 @@ protected:
do_traverse(Traverse* traverse);
bool
+ do_is_zero_value() const;
+
+ bool
do_is_static_initializer() const;
Type*
Index: gcc/go/gofrontend/runtime.def
===================================================================
--- gcc/go/gofrontend/runtime.def (revision 270780)
+++ gcc/go/gofrontend/runtime.def (working copy)
@@ -313,6 +313,14 @@ DEF_GO_RUNTIME(GCWRITEBARRIER, "runtime.
DEF_GO_RUNTIME(TYPEDMEMMOVE, "runtime.typedmemmove",
P3(TYPE, POINTER, POINTER), R0())
+// Clear memory that contains no pointer.
+DEF_GO_RUNTIME(MEMCLRNOPTR, "runtime.memclrNoHeapPointers",
+ P2(POINTER, UINTPTR), R0())
+
+// Clear memory that contains pointer.
+DEF_GO_RUNTIME(MEMCLRHASPTR, "runtime.memclrHasPointers",
+ P2(POINTER, UINTPTR), R0())
+
// Lock the printer (for print/println).
DEF_GO_RUNTIME(PRINTLOCK, "runtime.printlock", P0(), R0())
Index: gcc/go/gofrontend/statements.cc
===================================================================
--- gcc/go/gofrontend/statements.cc (revision 270780)
+++ gcc/go/gofrontend/statements.cc (working copy)
@@ -5516,6 +5516,21 @@ For_range_statement::do_lower(Gogo* gogo
return Statement::make_block_statement(temp_block, loc);
}
}
+ else if (range_type->array_type() != NULL)
+ {
+ // Slice or array.
+ Statement* clear = this->lower_array_range_clear(gogo,
+ range_type,
+ orig_range_expr,
+ temp_block,
+ range_object,
+ range_temp, loc);
+ if (clear != NULL)
+ {
+ temp_block->add_statement(clear);
+ return Statement::make_block_statement(temp_block, loc);
+ }
+ }
Temporary_statement* index_temp = Statement::make_temporary(index_type,
NULL, loc);
@@ -6237,6 +6252,109 @@ For_range_statement::lower_map_range_cle
return Statement::make_statement(call, true);
}
+// Match
+//
+// for i := range a { a[i] = zero }
+//
+// Lower it to call memclr on match, and return the statement. Return
+// NULL otherwise.
+
+Statement*
+For_range_statement::lower_array_range_clear(Gogo* gogo,
+ Type* array_type,
+ Expression* orig_range_expr,
+ Block* temp_block,
+ Named_object* range_object,
+ Temporary_statement* range_temp,
+ Location loc)
+{
+ if (this->value_var_ != NULL)
+ return NULL;
+ if (this->index_var_ == NULL)
+ return NULL;
+
+ // Match the body, a single assignment statement a[i] = zero.
+ const std::vector<Statement*>* statements = this->statements_->statements();
+ if (statements->size() != 1)
+ return NULL;
+ Assignment_statement* as = statements->at(0)->assignment_statement();
+ if (as == NULL || !as->rhs()->is_zero_value())
+ return NULL;
+ if (as->lhs()->type()->interface_type() != NULL
+ && as->rhs()->type()->interface_type() == NULL
+ && !as->rhs()->type()->is_nil_type())
+ // Implicit type conversion may change a zero value to non-zero, like
+ // interface{}(0).
+ return NULL;
+ Array_index_expression* aie = as->lhs()->array_index_expression();
+ if (aie == NULL || aie->end() != NULL
+ || !Expression::is_same_variable(orig_range_expr, aie->array())
+ || !Expression::is_same_variable(this->index_var_, aie->start()))
+ return NULL;
+
+ // Everything matches. Rewrite to
+ //
+ // if len(a) != 0 {
+ // tmp1 = &a[0]
+ // tmp2 = len(a)*sizeof(elem(a))
+ // memclr{NoHeap,Has}Pointers(tmp1, tmp2)
+ // i = len(a) - 1
+ // }
+
+ Type* elem_type = array_type->array_type()->element_type();
+ int64_t elme_sz;
+ bool ok = elem_type->backend_type_size(gogo, &elme_sz);
+ if (!ok)
+ return NULL;
+
+ Block* b = new Block(temp_block, loc);
+
+ Expression* ref;
+ if (range_object == NULL && range_temp == NULL)
+ // is_same_variable implies no side effect, so it is ok to copy.
+ ref = orig_range_expr->copy();
+ else
+ ref = this->make_range_ref(range_object, range_temp, loc);
+ Expression* len = this->call_builtin(gogo, "len", ref, loc);
+ Temporary_statement* tslen = Statement::make_temporary(NULL, len, loc);
+ temp_block->add_statement(tslen);
+
+ Expression* zero = Expression::make_integer_ul(0, this->index_var_->type(),
loc);
+ ref = ref->copy();
+ Expression* elem = Expression::make_array_index(ref, zero, NULL, NULL, loc);
+ elem->array_index_expression()->set_needs_bounds_check(false);
+ Expression* e1 = Expression::make_unary(OPERATOR_AND, elem, loc);
+ Temporary_statement* ts1 = Statement::make_temporary(NULL, e1, loc);
+ b->add_statement(ts1);
+
+ len = Expression::make_temporary_reference(tslen, loc);
+ Expression* sz = Expression::make_integer_int64(elme_sz, len->type(), loc);
+ Expression* e2 = Expression::make_binary(OPERATOR_MULT, len, sz, loc);
+ Temporary_statement* ts2 = Statement::make_temporary(NULL, e2, loc);
+ b->add_statement(ts2);
+
+ Expression* arg1 = Expression::make_temporary_reference(ts1, loc);
+ Expression* arg2 = Expression::make_temporary_reference(ts2, loc);
+ Runtime::Function code = (elem_type->has_pointer()
+ ? Runtime::MEMCLRHASPTR
+ : Runtime::MEMCLRNOPTR);
+ Expression* call = Runtime::make_call(code, loc, 2, arg1, arg2);
+ Statement* cs3 = Statement::make_statement(call, true);
+ b->add_statement(cs3);
+
+ len = Expression::make_temporary_reference(tslen, loc);
+ Expression* one = Expression::make_integer_ul(1, len->type(), loc);
+ Expression* rhs = Expression::make_binary(OPERATOR_MINUS, len, one, loc);
+ Expression* lhs = this->index_var_->copy();
+ Statement* as4 = Statement::make_assignment(lhs, rhs, loc);
+ b->add_statement(as4);
+
+ len = Expression::make_temporary_reference(tslen, loc);
+ zero = zero->copy();
+ Expression* cond = Expression::make_binary(OPERATOR_NOTEQ, len, zero, loc);
+ return Statement::make_if_statement(cond, b, NULL, loc);
+}
+
// Return the break LABEL_EXPR.
Unnamed_label*
Index: gcc/go/gofrontend/statements.h
===================================================================
--- gcc/go/gofrontend/statements.h (revision 270780)
+++ gcc/go/gofrontend/statements.h (working copy)
@@ -1622,6 +1622,11 @@ class For_range_statement : public State
lower_map_range_clear(Type*, Block*, Expression*, Named_object*,
Temporary_statement*, Location);
+ Statement*
+ lower_array_range_clear(Gogo*, Type*, Expression*, Block*,
+ Named_object*, Temporary_statement*,
+ Location);
+
// The variable which is set to the index value.
Expression* index_var_;
// The variable which is set to the element value. This may be
Index: libgo/go/runtime/mbarrier.go
===================================================================
--- libgo/go/runtime/mbarrier.go (revision 270552)
+++ libgo/go/runtime/mbarrier.go (working copy)
@@ -23,6 +23,7 @@ import (
//
//go:linkname typedmemmove runtime.typedmemmove
//go:linkname typedslicecopy runtime.typedslicecopy
+//go:linkname memclrHasPointers runtime.memclrHasPointers
// Go uses a hybrid barrier that combines a Yuasa-style deletion
// barrier—which shades the object whose reference is being
