runtime/internal/atomic: remove bad go:noescape annotations on Loadp

The //go:noescape directive says that arguments don't leak at all,
which is too aggressive of a claim for functions that return pointers
derived from their parameters.

Remove the directive for now. Long term fix will require a new
directive that allows more fine-grained control over escape analysis
information supplied for functions implemented in assembly.

Also, update the BAD comments in the test cases for Loadp: we really
want that *ptr leaks to the result parameter, not that *ptr leaks to
the heap.

Updates #31525.

Change-Id: Ibfa61f2b70daa7ed3223056b57eeee777eef2e31
Reviewed-on: https://go-review.googlesource.com/c/go/+/172578
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

src/runtime/internal/atomic/atomic_arm.go

@@ -181,7 +181,7 @@ func armcas(ptr *uint32, old, new uint32) bool
 //go:noescape
 func Load(addr *uint32) uint32
 
-//go:noescape
+// NO go:noescape annotation; *addr escapes if result escapes (#31525)
 func Loadp(addr unsafe.Pointer) unsafe.Pointer
 
 //go:noescape

src/runtime/internal/atomic/atomic_arm64.go

@@ -32,7 +32,7 @@ func Load(ptr *uint32) uint32
 //go:noescape
 func Load64(ptr *uint64) uint64
 
-//go:noescape
+// NO go:noescape annotation; *ptr escapes if result escapes (#31525)
 func Loadp(ptr unsafe.Pointer) unsafe.Pointer
 
 //go:noescape

src/runtime/internal/atomic/atomic_mips64x.go

@@ -32,7 +32,7 @@ func Load(ptr *uint32) uint32
 //go:noescape
 func Load64(ptr *uint64) uint64
 
-//go:noescape
+// NO go:noescape annotation; *ptr escapes if result escapes (#31525)
 func Loadp(ptr unsafe.Pointer) unsafe.Pointer
 
 //go:noescape

src/runtime/internal/atomic/atomic_mipsx.go

@@ -116,7 +116,7 @@ func Xchguintptr(ptr *uintptr, new uintptr) uintptr
 //go:noescape
 func Load(ptr *uint32) uint32
 
-//go:noescape
+// NO go:noescape annotation; *ptr escapes if result escapes (#31525)
 func Loadp(ptr unsafe.Pointer) unsafe.Pointer
 
 //go:noescape

src/runtime/internal/atomic/atomic_ppc64x.go

@@ -32,7 +32,7 @@ func Load(ptr *uint32) uint32
 //go:noescape
 func Load64(ptr *uint64) uint64
 
-//go:noescape
+// NO go:noescape annotation; *ptr escapes if result escapes (#31525)
 func Loadp(ptr unsafe.Pointer) unsafe.Pointer
 
 //go:noescape

test/escape_runtime_atomic.go

@@ -13,8 +13,8 @@ import (
 	"unsafe"
 )
 
-// BAD: should be "leaking param content".
-func Loadp(addr unsafe.Pointer) unsafe.Pointer { // ERROR "leaking param: addr"
+// BAD: should always be "leaking param: addr to result ~r1 level=1$".
+func Loadp(addr unsafe.Pointer) unsafe.Pointer { // ERROR "leaking param: addr( to result ~r1 level=1)?$"
 	return atomic.Loadp(addr)
 }
 

test/escape_sync_atomic.go

@@ -13,8 +13,8 @@ import (
 	"unsafe"
 )
 
-// BAD: should be "leaking param content".
-func LoadPointer(addr *unsafe.Pointer) unsafe.Pointer { // ERROR "leaking param: addr"
+// BAD: should be "leaking param: addr to result ~r1 level=1$".
+func LoadPointer(addr *unsafe.Pointer) unsafe.Pointer { // ERROR "leaking param: addr$"
 	return atomic.LoadPointer(addr)
 }