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compiler: open code string equality

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Open code string equality with builtin memcmp. This allows
    further optimizations in the backend.
    
    Reviewed-on: https://go-review.googlesource.com/c/gofrontend/+/183538

From-SVN: r272624
This commit is contained in:
Ian Lance Taylor 2019-06-24 17:54:07 +00:00
parent d611cec3de
commit 609c7da9ab
5 changed files with 52 additions and 28 deletions
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2
gcc/go/gofrontend/MERGE
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@ -1,4 +1,4 @@
338e4baf88a4ae676205dff601dbef2d31b19d2d
89b442a0100286ee569b8d2562ce1b2ea602f7e7
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.

62
gcc/go/gofrontend/expressions.cc
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@ -6226,10 +6226,27 @@ Binary_expression::do_flatten(Gogo* gogo, Named_object*,
bool is_idiv_op = ((this->op_ == OPERATOR_DIV &&
left_type->integer_type() != NULL)
|| this->op_ == OPERATOR_MOD);
bool is_string_op = (left_type->is_string_type()
&& this->right_->type()->is_string_type());
if (is_string_op)
{
// Mark string([]byte) operands to reuse the backing store.
// String comparison does not keep the reference, so it is safe.
Type_conversion_expression* lce =
this->left_->conversion_expression();
if (lce != NULL && lce->expr()->type()->is_slice_type())
lce->set_no_copy(true);
Type_conversion_expression* rce =
this->right_->conversion_expression();
if (rce != NULL && rce->expr()->type()->is_slice_type())
rce->set_no_copy(true);
}
if (is_shift_op
|| (is_idiv_op
&& (gogo->check_divide_by_zero() || gogo->check_divide_overflow())))
&& (gogo->check_divide_by_zero() || gogo->check_divide_overflow()))
|| is_string_op)
{
if (!this->left_->is_variable() && !this->left_->is_constant())
{
@ -7217,19 +7234,42 @@ 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);
go_assert(left->is_variable() || left->is_constant());
go_assert(right->is_variable() || right->is_constant());
if (op == OPERATOR_EQEQ || op == OPERATOR_NOTEQ)
{
left = Runtime::make_call(Runtime::EQSTRING, location, 2,
left, right);
// (l.len == r.len
// ? (l.ptr == r.ptr ? true : memcmp(l.ptr, r.ptr, r.len) == 0)
// : false)
Expression* llen = Expression::make_string_info(left,
STRING_INFO_LENGTH,
location);
Expression* rlen = Expression::make_string_info(right,
STRING_INFO_LENGTH,
location);
Expression* leneq = Expression::make_binary(OPERATOR_EQEQ, llen, rlen,
location);
Expression* lptr = Expression::make_string_info(left->copy(),
STRING_INFO_DATA,
location);
Expression* rptr = Expression::make_string_info(right->copy(),
STRING_INFO_DATA,
location);
Expression* ptreq = Expression::make_binary(OPERATOR_EQEQ, lptr, rptr,
location);
Expression* btrue = Expression::make_boolean(true, location);
Expression* call = Runtime::make_call(Runtime::MEMCMP, location, 3,
lptr->copy(), rptr->copy(),
rlen->copy());
Type* int32_type = Type::lookup_integer_type("int32");
Expression* zero = Expression::make_integer_ul(0, int32_type, location);
Expression* cmp = Expression::make_binary(OPERATOR_EQEQ, call, zero,
location);
Expression* cond = Expression::make_conditional(ptreq, btrue, cmp,
location);
Expression* bfalse = Expression::make_boolean(false, location);
left = Expression::make_conditional(leneq, cond, bfalse, location);
right = Expression::make_boolean(true, location);
}
else

3
gcc/go/gofrontend/runtime.def
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@ -39,9 +39,6 @@ DEF_GO_RUNTIME(DECODERUNE, "runtime.decoderune", P2(STRING, INT),
DEF_GO_RUNTIME(CONCATSTRINGS, "runtime.concatstrings",
P3(POINTER, POINTER, INT), R1(STRING))
// Compare two strings for equality.
DEF_GO_RUNTIME(EQSTRING, "runtime.eqstring", P2(STRING, STRING), R1(BOOL))
// Compare two strings.
DEF_GO_RUNTIME(CMPSTRING, "runtime.cmpstring", P2(STRING, STRING), R1(INT))

1
libgo/go/runtime/alg.go
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@ -44,7 +44,6 @@ import (
//go:linkname ifacevaleq runtime.ifacevaleq
//go:linkname ifaceefaceeq runtime.ifaceefaceeq
//go:linkname efacevaleq runtime.efacevaleq
//go:linkname eqstring runtime.eqstring
//go:linkname cmpstring runtime.cmpstring
//
// Temporary to be called from C code.

12
libgo/go/runtime/stubs.go
View File

@ -273,18 +273,6 @@ func checkASM() bool {
return true
}
func eqstring(x, y string) bool {
a := stringStructOf(&x)
b := stringStructOf(&y)
if a.len != b.len {
return false
}
if a.str == b.str {
return true
}
return memequal(a.str, b.str, uintptr(a.len))
}
// For gccgo this is in the C code.
func osyield()