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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/161036">161036</a></dd>
<dt>Author</dt> <dd>mark.lam@apple.com</dd>
<dt>Date</dt> <dd>2013-12-23 16:25:14 -0800 (Mon, 23 Dec 2013)</dd>
</dl>
<h3>Log Message</h3>
<pre>CStack: Fix JSStack::grow(), shrink(), growSlowCase(), and setStackLimit().
https://bugs.webkit.org/show_bug.cgi?id=126188.
Not yet reviewed.
These functions were inappropriately mixing "end" and "top" pointer idioms.
Specifically:
1. growSlowCase() was comparing a newEnd pointer against m_commitTop, and
using this to compute the size that the stack needs to grow.
2. shrink() was wrongly computing excess capacity by subtracting
baseOfStack() (which is at high memory) from m_commitTop (which points
to lower memory). Also, baseOfStack() is an "end" pointer while
m_commitTop is a "top" pointer. This is a mismatch.
To fix this and simplify the code a bit, I changed all of these functions
to take a newTopOfStack pointer instead of a newEnd pointer, and adjusted
their callers where needed to pass the appropropriate pointer values.
* interpreter/JSStack.cpp:
(JSC::JSStack::growSlowCase):
* interpreter/JSStack.h:
* interpreter/JSStackInlines.h:
(JSC::JSStack::popFrame):
(JSC::JSStack::shrink):
(JSC::JSStack::grow):
(JSC::JSStack::setStackLimit):</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#branchesjsCStackSourceJavaScriptCoreChangeLog">branches/jsCStack/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#branchesjsCStackSourceJavaScriptCoreinterpreterJSStackcpp">branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.cpp</a></li>
<li><a href="#branchesjsCStackSourceJavaScriptCoreinterpreterJSStackh">branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.h</a></li>
<li><a href="#branchesjsCStackSourceJavaScriptCoreinterpreterJSStackInlinesh">branches/jsCStack/Source/JavaScriptCore/interpreter/JSStackInlines.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="branchesjsCStackSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: branches/jsCStack/Source/JavaScriptCore/ChangeLog (161035 => 161036)</h4>
<pre class="diff"><span>
<span class="info">--- branches/jsCStack/Source/JavaScriptCore/ChangeLog 2013-12-24 00:20:47 UTC (rev 161035)
+++ branches/jsCStack/Source/JavaScriptCore/ChangeLog 2013-12-24 00:25:14 UTC (rev 161036)
</span><span class="lines">@@ -1,5 +1,34 @@
</span><span class="cx"> 2013-12-23 Mark Lam <mark.lam@apple.com>
</span><span class="cx">
</span><ins>+ CStack: Fix JSStack::grow(), shrink(), growSlowCase(), and setStackLimit().
+ https://bugs.webkit.org/show_bug.cgi?id=126188.
+
+ Not yet reviewed.
+
+ These functions were inappropriately mixing "end" and "top" pointer idioms.
+ Specifically:
+ 1. growSlowCase() was comparing a newEnd pointer against m_commitTop, and
+ using this to compute the size that the stack needs to grow.
+ 2. shrink() was wrongly computing excess capacity by subtracting
+ baseOfStack() (which is at high memory) from m_commitTop (which points
+ to lower memory). Also, baseOfStack() is an "end" pointer while
+ m_commitTop is a "top" pointer. This is a mismatch.
+
+ To fix this and simplify the code a bit, I changed all of these functions
+ to take a newTopOfStack pointer instead of a newEnd pointer, and adjusted
+ their callers where needed to pass the appropropriate pointer values.
+
+ * interpreter/JSStack.cpp:
+ (JSC::JSStack::growSlowCase):
+ * interpreter/JSStack.h:
+ * interpreter/JSStackInlines.h:
+ (JSC::JSStack::popFrame):
+ (JSC::JSStack::shrink):
+ (JSC::JSStack::grow):
+ (JSC::JSStack::setStackLimit):
+
+2013-12-23 Mark Lam <mark.lam@apple.com>
+
</ins><span class="cx"> CStack: Cosmetic: rename JSStack::m_commitEnd to m_commitTop.
</span><span class="cx"> https://bugs.webkit.org/show_bug.cgi?id=126186
</span><span class="cx">
</span></span></pre></div>
<a id="branchesjsCStackSourceJavaScriptCoreinterpreterJSStackcpp"></a>
<div class="modfile"><h4>Modified: branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.cpp (161035 => 161036)</h4>
<pre class="diff"><span>
<span class="info">--- branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.cpp 2013-12-24 00:20:47 UTC (rev 161035)
+++ branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.cpp 2013-12-24 00:25:14 UTC (rev 161036)
</span><span class="lines">@@ -77,19 +77,19 @@
</span><span class="cx"> m_reservation.deallocate();
</span><span class="cx"> }
</span><span class="cx">
</span><del>-bool JSStack::growSlowCase(Register* newEnd)
</del><ins>+bool JSStack::growSlowCase(Register* newTopOfStack)
</ins><span class="cx"> {
</span><span class="cx"> // If we have already committed enough memory to satisfy this request,
</span><span class="cx"> // just update the end pointer and return.
</span><del>- if (newEnd >= m_commitTop) {
- setStackLimit(newEnd);
</del><ins>+ if (newTopOfStack >= m_commitTop) {
+ setStackLimit(newTopOfStack);
</ins><span class="cx"> return true;
</span><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> // Compute the chunk size of additional memory to commit, and see if we
</span><span class="cx"> // have it is still within our budget. If not, we'll fail to grow and
</span><span class="cx"> // return false.
</span><del>- long delta = roundUpAllocationSize(reinterpret_cast<char*>(m_commitTop) - reinterpret_cast<char*>(newEnd), commitSize);
</del><ins>+ long delta = roundUpAllocationSize(reinterpret_cast<char*>(m_commitTop) - reinterpret_cast<char*>(newTopOfStack), commitSize);
</ins><span class="cx"> if (reinterpret_cast<char*>(m_commitTop) - delta <= reinterpret_cast<char*>(m_useableTop))
</span><span class="cx"> return false;
</span><span class="cx">
</span><span class="lines">@@ -98,7 +98,7 @@
</span><span class="cx"> m_reservation.commit(reinterpret_cast<char*>(m_commitTop) - delta, delta);
</span><span class="cx"> addToCommittedByteCount(delta);
</span><span class="cx"> m_commitTop = reinterpret_cast_ptr<Register*>(reinterpret_cast<char*>(m_commitTop) - delta);
</span><del>- setStackLimit(newEnd);
</del><ins>+ setStackLimit(newTopOfStack);
</ins><span class="cx"> return true;
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre></div>
<a id="branchesjsCStackSourceJavaScriptCoreinterpreterJSStackh"></a>
<div class="modfile"><h4>Modified: branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.h (161035 => 161036)</h4>
<pre class="diff"><span>
<span class="info">--- branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.h 2013-12-24 00:20:47 UTC (rev 161035)
+++ branches/jsCStack/Source/JavaScriptCore/interpreter/JSStack.h 2013-12-24 00:25:14 UTC (rev 161036)
</span><span class="lines">@@ -160,13 +160,13 @@
</span><span class="cx"> void installTrapsAfterFrame(CallFrame*) { }
</span><span class="cx"> #endif
</span><span class="cx">
</span><del>- bool grow(Register* topOfStack);
- bool growSlowCase(Register*);
- void shrink(Register*);
</del><ins>+ bool grow(Register* newTopOfStack);
+ bool growSlowCase(Register* newTopOfStack);
+ void shrink(Register* newTopOfStack);
</ins><span class="cx"> void releaseExcessCapacity();
</span><span class="cx"> void addToCommittedByteCount(long);
</span><span class="cx">
</span><del>- void setStackLimit(Register* newEnd);
</del><ins>+ void setStackLimit(Register* newTopOfStack);
</ins><span class="cx"> #endif // ENABLE(LLINT_C_LOOP)
</span><span class="cx">
</span><span class="cx"> void enableErrorStackReserve();
</span></span></pre></div>
<a id="branchesjsCStackSourceJavaScriptCoreinterpreterJSStackInlinesh"></a>
<div class="modfile"><h4>Modified: branches/jsCStack/Source/JavaScriptCore/interpreter/JSStackInlines.h (161035 => 161036)</h4>
<pre class="diff"><span>
<span class="info">--- branches/jsCStack/Source/JavaScriptCore/interpreter/JSStackInlines.h 2013-12-24 00:20:47 UTC (rev 161035)
+++ branches/jsCStack/Source/JavaScriptCore/interpreter/JSStackInlines.h 2013-12-24 00:25:14 UTC (rev 161036)
</span><span class="lines">@@ -166,33 +166,35 @@
</span><span class="cx"> // this case, we're shrinking all the way to the beginning since there
</span><span class="cx"> // are no more frames on the stack.
</span><span class="cx"> if (!callerFrame)
</span><del>- shrink(baseOfStack());
</del><ins>+ shrink(highAddress());
</ins><span class="cx">
</span><span class="cx"> installTrapsAfterFrame(callerFrame);
</span><span class="cx"> }
</span><span class="cx">
</span><del>-inline void JSStack::shrink(Register* newEnd)
</del><ins>+inline void JSStack::shrink(Register* newTopOfStack)
</ins><span class="cx"> {
</span><ins>+ Register* newEnd = newTopOfStack - 1;
</ins><span class="cx"> if (newEnd >= m_end)
</span><span class="cx"> return;
</span><del>- setStackLimit(newEnd);
- if (m_end == baseOfStack() && (m_commitTop - baseOfStack()) >= maxExcessCapacity)
</del><ins>+ setStackLimit(newTopOfStack);
+ if (m_end == baseOfStack() && (highAddress() - m_commitTop) >= maxExcessCapacity)
</ins><span class="cx"> releaseExcessCapacity();
</span><span class="cx"> }
</span><span class="cx">
</span><del>-inline bool JSStack::grow(Register* topOfStack)
</del><ins>+inline bool JSStack::grow(Register* newTopOfStack)
</ins><span class="cx"> {
</span><del>- Register* newEnd = topOfStack - 1;
</del><ins>+ Register* newEnd = newTopOfStack - 1;
</ins><span class="cx"> if (newEnd >= m_end)
</span><span class="cx"> return true;
</span><del>- return growSlowCase(newEnd);
</del><ins>+ return growSlowCase(newTopOfStack);
</ins><span class="cx"> }
</span><span class="cx">
</span><del>-inline void JSStack::setStackLimit(Register* newEnd)
</del><ins>+inline void JSStack::setStackLimit(Register* newTopOfStack)
</ins><span class="cx"> {
</span><ins>+ Register* newEnd = newTopOfStack - 1;
</ins><span class="cx"> m_end = newEnd;
</span><span class="cx"> #if ENABLE(LLINT_C_LOOP)
</span><del>- m_vm.setJSStackLimit(newEnd + 1);
</del><ins>+ m_vm.setJSStackLimit(newTopOfStack);
</ins><span class="cx"> #endif
</span><span class="cx"> }
</span><span class="cx">
</span></span></pre>
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