[v24.x] deps: V8: backport d259a9e2ead7 - #63865

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[v24.x] deps: V8: backport d259a9e2ead7#63865
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Backports v8/v8@d259a9e to the V8 13.6 tree.

Changes only impact when running with profiling enabled.

Fixes: #63816

Adaptation

One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.

Profiling with samply

samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js

Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.

Example

loop.js

When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.

Before

image

After

image

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Review requested:

  • @nodejs/gyp
  • @nodejs/security-wg
  • @nodejs/v8-update

@nodejs-github-botnodejs-github-bot added build Issues and PRs related to Node.js builds or CI infrastructure. needs-ci PRs that need a full CI run. v24.x Issues that can be reproduced on v24.x or PRs targeting the v24.x-staging branch. v8 engine Issues and PRs related to the V8 dependency. labels Jun 12, 2026
@aduh95
aduh95 changed the base branch from v24.x to v24.x-stagingJune 12, 2026 08:21
@aduh95aduh95 changed the title deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
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aduh95force-pushed the maglev-srcpos-backport branch from 6159ef6 to f437facCompareAugust 13, 2026 09:25
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CI: https://ci.nodejs.org/job/node-test-pull-request/75810/

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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=benchmark-ubuntu2404-intel-64,v8test=v8test/7308/

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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-power9le,v8test=v8test/7308/

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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-s390x,v8test=v8test/7308/

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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/

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@nodejs/v8 no objections for this backport?

@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
aduh95force-pushed the maglev-srcpos-backport branch from f437fac to 82a0233CompareAugust 19, 2026 09:33
@aduh95
aduh95 merged commit 82a0233 into nodejs:v24.x-stagingAug 19, 2026
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@GuillaumeLagrange@nodejs-github-bot@aduh95@LeszekSwirski
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
[v24.x] deps: V8: backport d259a9e2ead7 - #63865
Merged
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
Merged
[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
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@GuillaumeLagrangeGuillaumeLagrange
commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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Review requested:
  •  @nodejs/gyp
  •  @nodejs/security-wg
  •  @nodejs/v8-update
@nodejs-github-botnodejs-github-bot
added

build
Issues and PRs related to Node.js builds or CI infrastructure.
needs-ci
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v24.x
Issues that can be reproduced on v24.x or PRs targeting the v24.x-staging branch.
v8 engine
Issues and PRs related to the V8 dependency.
labels
Jun 12, 2026
@aduh95
aduh95
changed the base branch from
v24.x
to
v24.x-stagingJune 12, 2026 08:21
@aduh95aduh95
changed the title
deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
@aduh95
aduh95force-pushed
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maglev-srcpos-backport
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CI: https://ci.nodejs.org/job/node-test-pull-request/75810/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=benchmark-ubuntu2404-intel-64,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-power9le,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-s390x,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
@aduh95
aduh95
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
aduh95force-pushed
the
maglev-srcpos-backport
branch
from
f437fac to
82a0233CompareAugust 19, 2026 09:33
@aduh95
aduh95
merged commit 82a0233
into
nodejs:v24.x-stagingAug 19, 2026
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@GuillaumeLagrange@nodejs-github-bot@aduh95@LeszekSwirski

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[v24.x] deps: V8: backport d259a9e2ead7 - #63865
Merged
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
Merged
[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
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@GuillaumeLagrange
@GuillaumeLagrangeGuillaumeLagrange
commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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Review requested:
  •  @nodejs/gyp
  •  @nodejs/security-wg
  •  @nodejs/v8-update
@nodejs-github-botnodejs-github-bot
added

build
Issues and PRs related to Node.js builds or CI infrastructure.
needs-ci
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v24.x
Issues that can be reproduced on v24.x or PRs targeting the v24.x-staging branch.
v8 engine
Issues and PRs related to the V8 dependency.
labels
Jun 12, 2026
@aduh95
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changed the base branch from
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@aduh95aduh95
changed the title
deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
aduh95force-pushed
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maglev-srcpos-backport
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@aduh95
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merged commit 82a0233
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[v24.x] deps: V8: backport d259a9e2ead7 - #63865
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GuillaumeLagrange:maglev-srcpos-backport
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[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
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commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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  •  @nodejs/gyp
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deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=benchmark-ubuntu2404-intel-64,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
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@GuillaumeLagrange@nodejs-github-bot@aduh95@LeszekSwirski

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

Skip to content
[v24.x] deps: V8: backport d259a9e2ead7 - #63865
Merged
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
Merged
[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
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commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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Review requested:
  •  @nodejs/gyp
  •  @nodejs/security-wg
  •  @nodejs/v8-update
@nodejs-github-botnodejs-github-bot
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Jun 12, 2026
@aduh95
aduh95
changed the base branch from
v24.x
to
v24.x-stagingJune 12, 2026 08:21
@aduh95aduh95
changed the title
deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
@aduh95
aduh95force-pushed
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maglev-srcpos-backport
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=benchmark-ubuntu2404-intel-64,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-s390x,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
aduh95force-pushed
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maglev-srcpos-backport
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@aduh95
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merged commit 82a0233
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@GuillaumeLagrange@nodejs-github-bot@aduh95@LeszekSwirski

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
[v24.x] deps: V8: backport d259a9e2ead7 - #63865
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aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
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[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
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GuillaumeLagrange:maglev-srcpos-backport
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commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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Review requested:
  •  @nodejs/gyp
  •  @nodejs/security-wg
  •  @nodejs/v8-update
@nodejs-github-botnodejs-github-bot
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build
Issues and PRs related to Node.js builds or CI infrastructure.
needs-ci
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changed the title
deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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[v24.x] deps: V8: backport d259a9e2ead7 - #63865
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GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
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[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
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GuillaumeLagrange:maglev-srcpos-backport
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Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
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CI: https://ci.nodejs.org/job/node-test-pull-request/75810/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=benchmark-ubuntu2404-intel-64,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-power9le,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-s390x,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
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@aduh95
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merged commit 82a0233
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@GuillaumeLagrange@nodejs-github-bot@aduh95@LeszekSwirski

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
[v24.x] deps: V8: backport d259a9e2ead7 - #63865
Merged
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Aug 19, 2026
Merged
[v24.x] deps: V8: backport d259a9e2ead7#63865
aduh95 merged 1 commit into
nodejs:v24.x-stagingfrom 
GuillaumeLagrange:maglev-srcpos-backport
Conversation
@GuillaumeLagrange
@GuillaumeLagrangeGuillaumeLagrange
commented
Jun 12, 2026•

edited by aduh95

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Backports v8/v8@d259a9e to the V8 13.6 tree.
Changes only impact when running with profiling enabled.
Fixes: #63816
Adaptation
One deviation from a straight cherry-pick: upstream adds collect_source_positions() to a single graph-labeller condition in MaglevCompiler::Compile. The 13.6 tree builds the labeller in a differently shaped block, so the condition is added separately. Noted inline.
Profiling with samply
samply record -- ./node \
--perf-prof --interpreted-frames-native-stack \
--detailed-line-info --no-enable-lazy-source-positions \
your-script.js
Before this change, Maglev (+) frames resolve to a function name with no line detail. After, samples inside Maglev code map to their source lines and the inlined functions they came from.
Example
loop.js
When running this script, here's the before and after flamegraphs recorded with samply for convenience, but similar results can be achieved with perf + folding scripts.
Before
image
After
image
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Review requested:
  •  @nodejs/gyp
  •  @nodejs/security-wg
  •  @nodejs/v8-update
@nodejs-github-botnodejs-github-bot
added

build
Issues and PRs related to Node.js builds or CI infrastructure.
needs-ci
PRs that need a full CI run.
v24.x
Issues that can be reproduced on v24.x or PRs targeting the v24.x-staging branch.
v8 engine
Issues and PRs related to the V8 dependency.
labels
Jun 12, 2026
@aduh95
aduh95
changed the base branch from
v24.x
to
v24.x-stagingJune 12, 2026 08:21
@aduh95aduh95
changed the title
deps: V8: backport d259a9e2ead7[v24.x] deps: V8: backport d259a9e2ead7Jun 12, 2026
@aduh95
aduh95force-pushed
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maglev-srcpos-backport
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-s390x,v8test=v8test/7308/
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V8 CI: https://ci.nodejs.org/job/node-test-commit-v8-linux/nodes=rhel8-ppc64le,v8test=v8test/7308/
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@nodejs/v8 no objections for this backport?
@LeszekSwirski@GuillaumeLagrange@aduh95
deps: V8: backport d259a9e2ead7
82a0233
Original commit message:
[maglev] Add source position collection
This change adds support for collecting source positions in Maglev for
profiling. It wires a SourcePositionTableBuilder through the code
generator and uses the existing source positions from the graph
labeller.
Fixed: 436575053
Change-Id: I64fa1e8829b036e498fa1d756c996716d16fb2a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6897146
Reviewed-by: Victor Gomes <victorgomes@chromium.org>
Auto-Submit: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/main@{#102119}
Before this change Maglev attached an empty source position table to its
generated Code objects (set_empty_source_position_table()). As a result,
when profiling with `--perf-prof --interpreted-frames-native-stack`
(linux perf / samply), Maglev-optimized frames carried no line/inlining
information in the jitdump, so inlined call chains were lost in the
resulting flamegraphs (baseline and TurboFan code were unaffected). This
backport restores per-pc source positions for Maglev code, matching V8
>= 15.x and newer Node.js.
The change is gated on collect_source_positions() (enabled by
--detailed-line-info / profiling); the steady-state generated machine
code is unchanged and there is no extra cost when not profiling.
Adaptations for V8 13.6 (node): the graph-labeller creation in
MaglevCompiler::Compile is added as a separate condition because node's
13.6 tree creates the labeller in a differently-shaped block than
upstream; the rest is a direct cherry-pick.
Refs: v8/v8@d259a9eFixes: nodejs#63816
PR-URL: nodejs#63865
Co-authored-by: Guillaume Lagrange <guillaume@codspeed.io>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
@aduh95
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maglev-srcpos-backport
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@aduh95
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merged commit 82a0233
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