From 3407d1658f7d60cfb78293d61dfc21258efb0074 Mon Sep 17 00:00:00 2001 From: Cherry Zhang Date: Wed, 8 May 2019 23:06:52 +0000 Subject: [PATCH] compiler: avoid copy for string([]byte) conversion used in string comparison If a string([]byte) conversion is used immediately in a string comparison, we don't need to copy the backing store of the byte slice, as the string comparison doesn't hold any reference to it. Instead, just create a string header from the byte slice and pass it for comparison. A new type of expression, String_value_expression, is introduced, for constructing string headers. Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/170894 * go.dg/cmpstring.go: New test. From-SVN: r271021 --- gcc/go/gofrontend/MERGE | 2 +- gcc/go/gofrontend/expressions.cc | 118 +++++++++++++++++++++++++++++-- gcc/go/gofrontend/expressions.h | 17 ++++- gcc/testsuite/ChangeLog | 4 ++ gcc/testsuite/go.dg/cmpstring.go | 13 ++++ 5 files changed, 148 insertions(+), 6 deletions(-) create mode 100644 gcc/testsuite/go.dg/cmpstring.go diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE index 7c884a988da..f6f28a39ee3 100644 --- a/gcc/go/gofrontend/MERGE +++ b/gcc/go/gofrontend/MERGE @@ -1,4 +1,4 @@ -f813c670deb8e0454c3f64de74bedb5dcedd10b4 +9c8581187b1c1a30036263728370f31cb846a274 The first line of this file holds the git revision number of the last merge done from the gofrontend repository. diff --git a/gcc/go/gofrontend/expressions.cc b/gcc/go/gofrontend/expressions.cc index 707636ab6b1..2c1286cbdb0 100644 --- a/gcc/go/gofrontend/expressions.cc +++ b/gcc/go/gofrontend/expressions.cc @@ -2031,6 +2031,90 @@ Expression::make_string_info(Expression* string, String_info string_info, return new String_info_expression(string, string_info, location); } +// An expression that represents an string value: a struct with value pointer +// and length fields. + +class String_value_expression : public Expression +{ + public: + String_value_expression(Expression* valptr, Expression* len, Location location) + : Expression(EXPRESSION_STRING_VALUE, location), + valptr_(valptr), len_(len) + { } + + protected: + int + do_traverse(Traverse*); + + Type* + do_type() + { return Type::make_string_type(); } + + void + do_determine_type(const Type_context*) + { go_unreachable(); } + + Expression* + do_copy() + { + return new String_value_expression(this->valptr_->copy(), + this->len_->copy(), + this->location()); + } + + Bexpression* + do_get_backend(Translate_context* context); + + void + do_dump_expression(Ast_dump_context*) const; + + private: + // The value pointer. + Expression* valptr_; + // The length. + Expression* len_; +}; + +int +String_value_expression::do_traverse(Traverse* traverse) +{ + if (Expression::traverse(&this->valptr_, traverse) == TRAVERSE_EXIT + || Expression::traverse(&this->len_, traverse) == TRAVERSE_EXIT) + return TRAVERSE_EXIT; + return TRAVERSE_CONTINUE; +} + +Bexpression* +String_value_expression::do_get_backend(Translate_context* context) +{ + std::vector vals(2); + vals[0] = this->valptr_->get_backend(context); + vals[1] = this->len_->get_backend(context); + + Gogo* gogo = context->gogo(); + Btype* btype = Type::make_string_type()->get_backend(gogo); + return gogo->backend()->constructor_expression(btype, vals, this->location()); +} + +void +String_value_expression::do_dump_expression( + Ast_dump_context* ast_dump_context) const +{ + ast_dump_context->ostream() << "stringvalue("; + ast_dump_context->ostream() << "value: "; + this->valptr_->dump_expression(ast_dump_context); + ast_dump_context->ostream() << ", length: "; + this->len_->dump_expression(ast_dump_context); + ast_dump_context->ostream() << ")"; +} + +Expression* +Expression::make_string_value(Expression* valptr, Expression* len, + Location location) +{ + return new String_value_expression(valptr, len, location); +} + // Make an integer expression. class Integer_expression : public Expression @@ -3702,9 +3786,11 @@ Type_conversion_expression::do_check_types(Gogo*) Expression* Type_conversion_expression::do_copy() { - return new Type_conversion_expression(this->type_->copy_expressions(), - this->expr_->copy(), - this->location()); + Expression* ret = new Type_conversion_expression(this->type_->copy_expressions(), + this->expr_->copy(), + this->location()); + ret->conversion_expression()->set_no_copy(this->no_copy_); + return ret; } // Get the backend representation for a type conversion. @@ -3764,7 +3850,22 @@ Type_conversion_expression::do_get_backend(Translate_context* context) Runtime::Function code; if (e->integer_type()->is_byte()) - code = Runtime::SLICEBYTETOSTRING; + { + if (this->no_copy_) + { + if (gogo->debug_optimization()) + go_inform(loc, "no copy string([]byte)"); + Expression* ptr = Expression::make_slice_info(this->expr_, + SLICE_INFO_VALUE_POINTER, + loc); + Expression* len = Expression::make_slice_info(this->expr_, + SLICE_INFO_LENGTH, + loc); + Expression* str = Expression::make_string_value(ptr, len, loc); + return str->get_backend(context); + } + code = Runtime::SLICEBYTETOSTRING; + } else { go_assert(e->integer_type()->is_rune()); @@ -6805,6 +6906,15 @@ Expression::comparison(Translate_context* context, Type* result_type, if (left_type->is_string_type() && right_type->is_string_type()) { + // Mark string([]byte) operands to reuse the backing store. + // String comparison does not keep the reference, so it is safe. + Type_conversion_expression* lce = left->conversion_expression(); + if (lce != NULL && lce->expr()->type()->is_slice_type()) + lce->set_no_copy(true); + Type_conversion_expression* rce = right->conversion_expression(); + if (rce != NULL && rce->expr()->type()->is_slice_type()) + rce->set_no_copy(true); + if (op == OPERATOR_EQEQ || op == OPERATOR_NOTEQ) { left = Runtime::make_call(Runtime::EQSTRING, location, 2, diff --git a/gcc/go/gofrontend/expressions.h b/gcc/go/gofrontend/expressions.h index 7d3cfd85a3f..2cca8240fcd 100644 --- a/gcc/go/gofrontend/expressions.h +++ b/gcc/go/gofrontend/expressions.h @@ -102,6 +102,7 @@ class Expression EXPRESSION_BOOLEAN, EXPRESSION_STRING, EXPRESSION_STRING_INFO, + EXPRESSION_STRING_VALUE, EXPRESSION_INTEGER, EXPRESSION_FLOAT, EXPRESSION_COMPLEX, @@ -248,6 +249,10 @@ class Expression static Expression* make_string_info(Expression* string, String_info, Location); + // Make an expression for a string value. + static Expression* + make_string_value(Expression* valptr, Expression* len, Location); + // Make a character constant expression. TYPE should be NULL for an // abstract type. static Expression* @@ -1668,7 +1673,8 @@ class Type_conversion_expression : public Expression Type_conversion_expression(Type* type, Expression* expr, Location location) : Expression(EXPRESSION_CONVERSION, location), - type_(type), expr_(expr), may_convert_function_types_(false) + type_(type), expr_(expr), may_convert_function_types_(false), + no_copy_(false) { } // Return the type to which we are converting. @@ -1689,6 +1695,12 @@ class Type_conversion_expression : public Expression this->may_convert_function_types_ = true; } + // Mark string([]byte) conversion to reuse the backing store + // without copying. + void + set_no_copy(bool b) + { this->no_copy_ = b; }; + // Import a type conversion expression. static Expression* do_import(Import_expression*, Location); @@ -1751,6 +1763,9 @@ class Type_conversion_expression : public Expression // True if this is permitted to convert function types. This is // used internally for method expressions. bool may_convert_function_types_; + // True if a string([]byte) conversion can reuse the backing store + // without copying. Only used in string([]byte) conversion. + bool no_copy_; }; // An unsafe type conversion, used to pass values to builtin functions. diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 797a370ef95..270453f247d 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,7 @@ +2019-05-08 Cherry Zhang + + * go.dg/cmpstring.go: New test. + 2019-05-08 Jakub Jelinek PR c++/59813 diff --git a/gcc/testsuite/go.dg/cmpstring.go b/gcc/testsuite/go.dg/cmpstring.go new file mode 100644 index 00000000000..81d8aee379d --- /dev/null +++ b/gcc/testsuite/go.dg/cmpstring.go @@ -0,0 +1,13 @@ +// { dg-do compile } +// { dg-options "-fgo-debug-optimization" } + +package p + +func F(x []byte, y string) bool { + return string(x) == y // { dg-error "no copy string\\(\\\[\\\]byte\\)" } +} + +func BytesEqual(x, y []byte) bool { + return string(x) == // { dg-error "no copy string\\(\\\[\\\]byte\\)" } + string(y) // { dg-error "no copy string\\(\\\[\\\]byte\\)" } +} -- 2.30.2