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cmd/compile: compile cap(ch) as call to runtime.chancap

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An upcoming CL will give this call more to do.
For now, separate out the compiler change that
stops inlining the computation.

For #37196.

Change-Id: I965426d446964b9b4958e4613246002a7660e7eb
Reviewed-on: https://go-review.googlesource.com/c/go/+/568375
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Auto-Submit: Russ Cox <rsc@golang.org>
This commit is contained in:
Russ Cox 2024-02-29 14:28:09 -05:00 committed by Gopher Robot
parent 24fa7544b0
commit 61d6817c83
5 changed files with 22 additions and 9 deletions
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3
src/cmd/compile/internal/ssagen/ssa.go
View File

@ -6350,6 +6350,9 @@ func (s *state) referenceTypeBuiltin(n *ir.UnaryExpr, x *ssa.Value) *ssa.Value {
if n.X.Type().IsChan() && n.Op() == ir.OLEN {
s.Fatalf("cannot inline len(chan)") // must use runtime.chanlen now
}
if n.X.Type().IsChan() && n.Op() == ir.OCAP {
s.Fatalf("cannot inline cap(chan)") // must use runtime.chancap now
}
// if n == nil {
// return 0
// } else {

1
src/cmd/compile/internal/typecheck/_builtin/runtime.go
View File

@ -161,6 +161,7 @@ func chanrecv2(hchan <-chan any, elem *any) bool
func chansend1(hchan chan<- any, elem *any)
func closechan(hchan chan<- any)
func chanlen(hchan any) int
func chancap(hchan any) int
var writeBarrier struct {
enabled bool

1
src/cmd/compile/internal/typecheck/builtin.go
View File

@ -138,6 +138,7 @@ var runtimeDecls = [...]struct {
{"chansend1", funcTag, 103},
{"closechan", funcTag, 104},
{"chanlen", funcTag, 105},
{"chancap", funcTag, 105},
{"writeBarrier", varTag, 107},
{"typedmemmove", funcTag, 108},
{"typedmemclr", funcTag, 109},

14
src/cmd/compile/internal/walk/builtin.go
View File

@ -261,10 +261,14 @@ func walkLenCap(n *ir.UnaryExpr, init *ir.Nodes) ir.Node {
_, len := backingArrayPtrLen(cheapExpr(conv.X, init))
return len
}
if isChanLen(n) {
if isChanLenCap(n) {
name := "chanlen"
if n.Op() == ir.OCAP {
name = "chancap"
}
// cannot use chanfn - closechan takes any, not chan any,
// because it accepts both send-only and recv-only channels.
fn := typecheck.LookupRuntime("chanlen", n.X.Type())
fn := typecheck.LookupRuntime(name, n.X.Type())
return mkcall1(fn, n.Type(), init, n.X)
}
@ -892,9 +896,9 @@ func isByteCount(n ir.Node) bool {
(n.(*ir.UnaryExpr).X.Op() == ir.OBYTES2STR || n.(*ir.UnaryExpr).X.Op() == ir.OBYTES2STRTMP)
}
// isChanLen reports whether n is of the form len(c) for a channel c.
// isChanLenCap reports whether n is of the form len(c) or cap(c) for a channel c.
// Note that this does not check for -n or instrumenting because this
// is a correctness rewrite, not an optimization.
func isChanLen(n ir.Node) bool {
return n.Op() == ir.OLEN && n.(*ir.UnaryExpr).X.Type().IsChan()
func isChanLenCap(n ir.Node) bool {
return (n.Op() == ir.OLEN || n.Op() == ir.OCAP) && n.(*ir.UnaryExpr).X.Type().IsChan()
}

12
src/runtime/chan.go
View File

@ -731,6 +731,13 @@ func chanlen(c *hchan) int {
return int(c.qcount)
}
func chancap(c *hchan) int {
if c == nil {
return 0
}
return int(c.dataqsiz)
}
//go:linkname reflect_chanlen reflect.chanlen
func reflect_chanlen(c *hchan) int {
return chanlen(c)
@ -743,10 +750,7 @@ func reflectlite_chanlen(c *hchan) int {
//go:linkname reflect_chancap reflect.chancap
func reflect_chancap(c *hchan) int {
if c == nil {
return 0
}
return int(c.dataqsiz)
return chancap(c)
}
//go:linkname reflect_chanclose reflect.chanclose