runtime: avoid write barriers when calling deferred function
Calling a deferred function currently requires changing from a uintptr
to the function code to a Go function value. That is done by setting
the value of a func local variable using unsafe.Pointer. The local
variable will always be on the stack. Adjust the code that sets the
local variable to avoid generating a write barrier.
A write barrier is never needed here. Also, for deferreturn, we must
avoid write barriers entirely when called from a cgo function; that
requires more than just this, but this is a start.
The test for this is runtime tests that use the go tool; these are not
currently run, but they will be in the future.
Change-Id: I762fd07b7fd5b46c0c54156f89c71fb60de53023
Reviewed-on: https://go-review.googlesource.com/46455
Reviewed-by: Than McIntosh <thanm@google.com>
diff --git a/libgo/go/runtime/panic.go b/libgo/go/runtime/panic.go
index bbd34b4..de3c79f 100644
--- a/libgo/go/runtime/panic.go
+++ b/libgo/go/runtime/panic.go
@@ -194,7 +194,7 @@
// The gc compiler does this using assembler
// code in jmpdefer.
var fn func(unsafe.Pointer)
- *(**uintptr)(unsafe.Pointer(&fn)) = &pfn
+ *(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
fn(d.arg)
}
@@ -259,7 +259,7 @@
gp._defer = d.link
var fn func(unsafe.Pointer)
- *(**uintptr)(unsafe.Pointer(&fn)) = &pfn
+ *(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
fn(d.arg)
freedefer(d)
@@ -345,7 +345,7 @@
if pfn != 0 {
var fn func(unsafe.Pointer)
- *(**uintptr)(unsafe.Pointer(&fn)) = &pfn
+ *(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
fn(d.arg)
}
@@ -446,7 +446,7 @@
if pfn != 0 {
var fn func(unsafe.Pointer)
- *(**uintptr)(unsafe.Pointer(&fn)) = &pfn
+ *(*uintptr)(unsafe.Pointer(&fn)) = uintptr(unsafe.Pointer(&pfn))
fn(d.arg)
if p.recovered {
