Issue 12689046: code review 12689046: cmd/cc, cmd/gc, runtime: Uniquely encode iface and efac...

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Issue 12689046: code review 12689046: cmd/cc, cmd/gc, runtime: Uniquely encode iface and efac... (Closed)

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Created:
11 years, 10 months ago by cshapiro1

Modified:
11 years, 10 months ago

Reviewers:
rsc

CC:
golang-dev, rsc

Visibility:
Public.

Description

cmd/cc, cmd/gc, runtime: Uniquely encode iface and eface pointers in the pointer map. Prior to this change, pointer maps encoded the disposition of a word using a single bit. A zero signaled a non-pointer value and a one signaled a pointer value. Interface values, which are a effectively a union type, were conservatively labeled as a pointer. This change widens the logical element size of the pointer map to two bits per word. As before, zero signals a non-pointer value and one signals a pointer value. Additionally, a two signals an iface pointer and a three signals an eface pointer. Following other changes to the runtime, values two and three will allow a type information to drive interpretation of the subsequent word so only those interface values containing a pointer value will be scanned.

	Unified diffs	Side-by-side diffs	Delta from patch set	Stats (+24 lines, -12 lines)			Patch
M	src/cmd/cc/pgen.c	View	1	4 chunks	+6 lines, -2 lines	0 comments	Download
M	src/cmd/gc/pgen.c	View	1	7 chunks	+11 lines, -7 lines	0 comments	Download
M	src/pkg/runtime/mgc0.c	View	1	3 chunks	+7 lines, -3 lines	0 comments	Download

Messages

Total messages: 3

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cshapiro1

Hello golang-dev@googlegroups.com, I'd like you to review this change to https://code.google.com/p/go/

11 years, 10 months ago (2013-08-09 22:34:24 UTC) #1

cshapiro1

11 years, 10 months ago (2013-08-09 23:48:15 UTC) #3

*** Submitted as https://code.google.com/p/go/source/detail?r=578fe4324aac ***

cmd/cc, cmd/gc, runtime: Uniquely encode iface and eface pointers in the pointer
map.

Prior to this change, pointer maps encoded the disposition of
a word using a single bit.  A zero signaled a non-pointer
value and a one signaled a pointer value.  Interface values,
which are a effectively a union type, were conservatively
labeled as a pointer.

This change widens the logical element size of the pointer map
to two bits per word.  As before, zero signals a non-pointer
value and one signals a pointer value.  Additionally, a two
signals an iface pointer and a three signals an eface pointer.

Following other changes to the runtime, values two and three
will allow a type information to drive interpretation of the
subsequent word so only those interface values containing a
pointer value will be scanned.

R=golang-dev, rsc
CC=golang-dev
https://codereview.appspot.com/12689046

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