* Go patch committed: Return two values from selectnbrecv
@ 2021-08-03 23:40 Ian Lance Taylor
0 siblings, 0 replies; only message in thread
From: Ian Lance Taylor @ 2021-08-03 23:40 UTC (permalink / raw)
To: gcc-patches, gofrontend-dev
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This patch to the Go frontend and libgo changes selectnbrecv to return
two values. The only difference between selectnbrecv and
selectnbrecv2 is that the latter uses a pointer argument as the second
return value from chanrecv. This patch changes selectnbrecv to return
the two values from chanrecv and gets
rid of selectnbrecv2. The compiler now calls only selectnbrecv, which
is simpler.
This is the gofrontend version of https://golang.org/cl/292890. I'm
committing it now as part of updating to the Go 1.17 release.
Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed
to mainline.
Ian
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e435e72ad713cadd661072427588ec1c777c04e3
diff --git a/gcc/go/gofrontend/MERGE b/gcc/go/gofrontend/MERGE
index 801e039a155..5a097ffee85 100644
--- a/gcc/go/gofrontend/MERGE
+++ b/gcc/go/gofrontend/MERGE
@@ -1,4 +1,4 @@
-54361805bd611d896042b879ee7f6d2d4d088537
+2031f0be9c0b5fda6421d290a0261eb6bd1c8205
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/runtime.def b/gcc/go/gofrontend/runtime.def
index fad8cebc012..87a27085d60 100644
--- a/gcc/go/gofrontend/runtime.def
+++ b/gcc/go/gofrontend/runtime.def
@@ -204,12 +204,8 @@ DEF_GO_RUNTIME(SELECTNBSEND, "runtime.selectnbsend", P2(CHAN, POINTER), R1(BOOL)
// Non-blocking receive a value from a channel, used for two-case select
// statement with a default case.
-DEF_GO_RUNTIME(SELECTNBRECV, "runtime.selectnbrecv", P2(POINTER, CHAN), R1(BOOL))
-
-// Non-blocking tuple receive from a channel, used for two-case select
-// statement with a default case.
-DEF_GO_RUNTIME(SELECTNBRECV2, "runtime.selectnbrecv2", P3(POINTER, POINTER, CHAN),
- R1(BOOL))
+DEF_GO_RUNTIME(SELECTNBRECV, "runtime.selectnbrecv", P2(POINTER, CHAN),
+ R2(BOOL, BOOL))
// Block execution. Used for zero-case select.
DEF_GO_RUNTIME(BLOCK, "runtime.block", P0(), R0())
diff --git a/gcc/go/gofrontend/statements.cc b/gcc/go/gofrontend/statements.cc
index 9643d1b42b3..95fa3c48709 100644
--- a/gcc/go/gofrontend/statements.cc
+++ b/gcc/go/gofrontend/statements.cc
@@ -6051,7 +6051,7 @@ Select_statement::lower_two_case(Block* b)
Expression* chanref = Expression::make_temporary_reference(chantmp, loc);
Block* bchan;
- Expression* call;
+ Expression* cond;
if (chancase.is_send())
{
// if selectnbsend(chan, &val) { body } else { default body }
@@ -6065,7 +6065,7 @@ Select_statement::lower_two_case(Block* b)
Expression* ref = Expression::make_temporary_reference(ts, loc);
Expression* addr = Expression::make_unary(OPERATOR_AND, ref, loc);
- call = Runtime::make_call(Runtime::SELECTNBSEND, loc, 2, chanref, addr);
+ cond = Runtime::make_call(Runtime::SELECTNBSEND, loc, 2, chanref, addr);
bchan = chancase.statements();
}
else
@@ -6075,34 +6075,31 @@ Select_statement::lower_two_case(Block* b)
Expression* ref = Expression::make_temporary_reference(ts, loc);
Expression* addr = Expression::make_unary(OPERATOR_AND, ref, loc);
- Expression* okref = NULL;
- if (chancase.closed() == NULL && chancase.closedvar() == NULL)
- {
- // Simple receive.
- // if selectnbrecv(&lhs, chan) { body } else { default body }
- call = Runtime::make_call(Runtime::SELECTNBRECV, loc, 2, addr, chanref);
- }
- else
- {
- // Tuple receive.
- // if selectnbrecv2(&lhs, &ok, chan) { body } else { default body }
-
- Type* booltype = Type::make_boolean_type();
- Temporary_statement* okts = Statement::make_temporary(booltype, NULL,
- loc);
- b->add_statement(okts);
-
- okref = Expression::make_temporary_reference(okts, loc);
- Expression* okaddr = Expression::make_unary(OPERATOR_AND, okref, loc);
- call = Runtime::make_call(Runtime::SELECTNBRECV2, loc, 3, addr, okaddr,
- chanref);
- }
+
+ // selected, ok = selectnbrecv(&lhs, chan)
+ Call_expression* call = Runtime::make_call(Runtime::SELECTNBRECV, loc, 2,
+ addr, chanref);
+
+ Temporary_statement* selected_temp =
+ Statement::make_temporary(Type::make_boolean_type(),
+ Expression::make_call_result(call, 0),
+ loc);
+ b->add_statement(selected_temp);
+
+ Temporary_statement* ok_temp =
+ Statement::make_temporary(Type::make_boolean_type(),
+ Expression::make_call_result(call, 1),
+ loc);
+ b->add_statement(ok_temp);
+
+ cond = Expression::make_temporary_reference(selected_temp, loc);
Location cloc = chancase.location();
bchan = new Block(b, loc);
if (chancase.val() != NULL && !chancase.val()->is_sink_expression())
{
- Statement* as = Statement::make_assignment(chancase.val(), ref->copy(),
+ Statement* as = Statement::make_assignment(chancase.val(),
+ ref->copy(),
cloc);
bchan->add_statement(as);
}
@@ -6114,12 +6111,18 @@ Select_statement::lower_two_case(Block* b)
if (chancase.closed() != NULL && !chancase.closed()->is_sink_expression())
{
+ Expression* okref = Expression::make_temporary_reference(ok_temp,
+ cloc);
Statement* as = Statement::make_assignment(chancase.closed(),
- okref->copy(), cloc);
+ okref, cloc);
bchan->add_statement(as);
}
else if (chancase.closedvar() != NULL)
- chancase.closedvar()->var_value()->set_init(okref->copy());
+ {
+ Expression* okref = Expression::make_temporary_reference(ok_temp,
+ cloc);
+ chancase.closedvar()->var_value()->set_init(okref);
+ }
Statement* bs = Statement::make_block_statement(chancase.statements(),
cloc);
@@ -6127,7 +6130,7 @@ Select_statement::lower_two_case(Block* b)
}
Statement* ifs =
- Statement::make_if_statement(call, bchan, defcase.statements(), loc);
+ Statement::make_if_statement(cond, bchan, defcase.statements(), loc);
b->add_statement(ifs);
Statement* label =
diff --git a/libgo/go/runtime/chan.go b/libgo/go/runtime/chan.go
index 7878a8fe012..e3d0ad5acbe 100644
--- a/libgo/go/runtime/chan.go
+++ b/libgo/go/runtime/chan.go
@@ -33,7 +33,6 @@ import (
//go:linkname closechan
//go:linkname selectnbsend
//go:linkname selectnbrecv
-//go:linkname selectnbrecv2
const (
maxAlign = 8
@@ -709,28 +708,6 @@ func selectnbsend(c *hchan, elem unsafe.Pointer) (selected bool) {
return chansend(c, elem, false, getcallerpc())
}
-// compiler implements
-//
-// select {
-// case v = <-c:
-// ... foo
-// default:
-// ... bar
-// }
-//
-// as
-//
-// if selectnbrecv(&v, c) {
-// ... foo
-// } else {
-// ... bar
-// }
-//
-func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected bool) {
- selected, _ = chanrecv(c, elem, false)
- return
-}
-
// compiler implements
//
// select {
@@ -742,16 +719,14 @@ func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected bool) {
//
// as
//
-// if c != nil && selectnbrecv2(&v, &ok, c) {
+// if selected, ok = selectnbrecv(&v, c); selected {
// ... foo
// } else {
// ... bar
// }
//
-func selectnbrecv2(elem unsafe.Pointer, received *bool, c *hchan) (selected bool) {
- // TODO(khr): just return 2 values from this function, now that it is in Go.
- selected, *received = chanrecv(c, elem, false)
- return
+func selectnbrecv(elem unsafe.Pointer, c *hchan) (selected, received bool) {
+ return chanrecv(c, elem, false)
}
//go:linkname reflect_chansend reflect.chansend
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2021-08-03 23:40 Go patch committed: Return two values from selectnbrecv Ian Lance Taylor
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