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Merged
EgorBo merged 4 commits into from
Jun 29, 2026
Merged

JIT: Tail-merge robust crossJumpVictim selection #129141

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d42fc3c
* add tie-break
BoyBaykiller Jun 8, 2026
a9d4d53
* remove explicit isNoGcPoll heuristic
BoyBaykiller Jun 9, 2026
b5bd36a
Merge branch 'main' into robust-crossJumpVictim
BoyBaykiller Jun 25, 2026
58079eb
* feedback
BoyBaykiller Jun 25, 2026
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69 changes: 31 additions & 38 deletions src/coreclr/jit/fgopt.cpp
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Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

BasicBlock* crossJumpVictim = nullptr;
Statement* crossJumpStmt = nullptr;
bool haveNoSplitVictim = false;
bool haveFallThroughVictim = false;
BasicBlock* crossJumpVictim = nullptr;
Statement* crossJumpStmt = nullptr;
unsigned bestRank = UINT32_MAX;

for (PredInfo& info : matchedPredInfo.TopDownOrder())
{
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
continue;
}

bool const isNoSplit = stmt == predBlock->firstStmt();
bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
auto getRank = [=]() -> unsigned {

@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.

bool const isNoSplit = stmt == predBlock->firstStmt();
bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

// Is this block possibly better than what we have?
//
bool useBlock = false;

if (crossJumpVictim == nullptr)
{
// Pick an initial candidate.
useBlock = true;
}
else if (isNoSplit && isFallThrough)
{
// This is the ideal choice.
// From most to least preferable.
//
useBlock = true;
}
else if (!haveNoSplitVictim && isNoSplit)
{
useBlock = true;
}
else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
{
useBlock = true;
}
if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.
{
return 0;
}
if (isNoSplit)
{
return 1;
}
if (isFallThrough)
{
return 2;
}

return 3;
};

if (useBlock)
unsigned const rank = getRank();
bool pick = rank < bestRank;
if (rank == bestRank)
{
crossJumpVictim = predBlock;
crossJumpStmt = stmt;
haveNoSplitVictim = isNoSplit;
haveFallThroughVictim = isFallThrough;
pick = predBlock->bbID < crossJumpVictim->bbID;
}

// If we have the perfect victim, stop looking.
//
if (haveNoSplitVictim && haveFallThroughVictim)
if (pick)
{
break;
crossJumpVictim = predBlock;
crossJumpStmt = stmt;
bestRank = rank;
}
}

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
// If this block requires splitting, then split it.
// Note we know that stmt has a prev stmt.
//
if (haveNoSplitVictim)
if (crossJumpStmt == crossJumpTarget->firstStmt())
{
JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
}
Expand Down
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
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(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
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;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
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JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

from

Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
 Changes from all commits
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4 commits


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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
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';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
Skip to content
JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

from

Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
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4 commits


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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
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style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
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} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
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JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

from

Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
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Commits

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4 commits


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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
Skip to content
JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

from

Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
 Changes from all commits
Commits

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4 commits


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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
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// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
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setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
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}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
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})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
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JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

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Jun 29, 2026
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JIT: Tail-merge robust crossJumpVictim selection
#129141
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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

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Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
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if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
Skip to content
JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

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Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
 Changes from all commits
Commits

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4 commits


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d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

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Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
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removeDarkMode();
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applyDarkMode();
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console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
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} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
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JIT: Tail-merge robust `crossJumpVictim` selection by BoyBaykiller · Pull Request #129141 · dotnet/runtime · GitHub
Skip to content
JIT: Tail-merge robust crossJumpVictim selection#129141

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 Merged

EgorBo
merged 4 commits into

from

Jun 29, 2026
 Merged


JIT: Tail-merge robust crossJumpVictim selection
#129141
 Changes from all commits
Commits

Show all changes


4 commits


Select commit
Hold shift + click to select a range
d42fc3c

* add tie-break


BoyBaykiller Jun 8, 2026
a9d4d53

* remove explicit isNoGcPoll heuristic


BoyBaykiller Jun 9, 2026
b5bd36a

Merge branch 'main' into robust-crossJumpVictim


BoyBaykiller Jun 25, 2026
58079eb

* feedback


BoyBaykiller Jun 25, 2026

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69 changes: 31 additions & 38 deletions
src/coreclr/jit/fgopt.cpp

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -5285,10 +5285,9 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)

 JITDUMPEXEC(gtDispStmt(matchedPredInfo.TopRef(0).m_stmt));

 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 bool haveNoSplitVictim = false;
 bool haveFallThroughVictim = false;
 BasicBlock* crossJumpVictim = nullptr;
 Statement* crossJumpStmt = nullptr;
 unsigned bestRank = UINT32_MAX;

 for (PredInfo& info : matchedPredInfo.TopDownOrder())
 {
Expand All@@ -5302,46 +5301,40 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 continue;
 }

 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());
 auto getRank = [=]() -> unsigned {
@EgorBoEgorBoJun 29, 2026

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Choose a reason for hiding this comment

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not sure I understand why you wrapped it to a single-use lambda, not a big fan of this approach.
 bool const isNoSplit = stmt == predBlock->firstStmt();
 bool const isFallThrough = (predBlock->KindIs(BBJ_ALWAYS) && predBlock->JumpsToNext());

 // Is this block possibly better than what we have?
 //
 bool useBlock = false;

 if (crossJumpVictim == nullptr)
 {
 // Pick an initial candidate.
 useBlock = true;
 }
 else if (isNoSplit && isFallThrough)
 {
 // This is the ideal choice.
 // From most to least preferable.
 //
 useBlock = true;
 }
 else if (!haveNoSplitVictim && isNoSplit)
 {
 useBlock = true;
 }
 else if (!haveNoSplitVictim && !haveFallThroughVictim && isFallThrough)
 {
 useBlock = true;
 }
 if (isNoSplit && isFallThrough)
Comment thread
BoyBaykiller marked this conversation as resolved.

 {
 return 0;
 }
 if (isNoSplit)
 {
 return 1;
 }
 if (isFallThrough)
 {
 return 2;
 }

 return 3;
 };

 if (useBlock)
 unsigned const rank = getRank();
 bool pick = rank < bestRank;
 if (rank == bestRank)
 {
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 haveNoSplitVictim = isNoSplit;
 haveFallThroughVictim = isFallThrough;
 pick = predBlock->bbID < crossJumpVictim->bbID;
 }

 // If we have the perfect victim, stop looking.
 //
 if (haveNoSplitVictim && haveFallThroughVictim)
 if (pick)
 {
 break;
 crossJumpVictim = predBlock;
 crossJumpStmt = stmt;
 bestRank = rank;
 }
 }

Expand All@@ -5350,7 +5343,7 @@ PhaseStatus Compiler::fgHeadTailMerge(bool early)
 // If this block requires splitting, then split it.
 // Note we know that stmt has a prev stmt.
 //
 if (haveNoSplitVictim)
 if (crossJumpStmt == crossJumpTarget->firstStmt())
 {
 JITDUMP("Will cross-jump to " FMT_BB "\n", crossJumpTarget->bbNum);
 }
Expand Down
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