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<dl class="meta">
<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/195707">195707</a></dd>
<dt>Author</dt> <dd>commit-queue@webkit.org</dd>
<dt>Date</dt> <dd>2016-01-27 16:29:09 -0800 (Wed, 27 Jan 2016)</dd>
</dl>
<h3>Log Message</h3>
<pre>[JSC] adjustFrameAndStackInOSRExitCompilerThunk() can trash values in FTL
https://bugs.webkit.org/show_bug.cgi?id=153536
Patch by Benjamin Poulain <bpoulain@apple.com> on 2016-01-27
Reviewed by Saam Barati.
Workaround to get B3 working on ARM.
* dfg/DFGOSRExitCompilerCommon.h:
(JSC::DFG::adjustFrameAndStackInOSRExitCompilerThunk):
The code was using the scratch registers in a few places.
I initially tried to make is not use scratch registers anywhere
but that looked super fragile.
Instead, I just preserve the scratch registers. That's easy and
it should be relatively cheap compared to everything done on OSR Exits.</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#trunkSourceJavaScriptCoreChangeLog">trunk/Source/JavaScriptCore/ChangeLog</a></li>
<li><a href="#trunkSourceJavaScriptCoredfgDFGOSRExitCompilerCommonh">trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompilerCommon.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunkSourceJavaScriptCoreChangeLog"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/ChangeLog (195706 => 195707)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/ChangeLog 2016-01-28 00:18:37 UTC (rev 195706)
+++ trunk/Source/JavaScriptCore/ChangeLog 2016-01-28 00:29:09 UTC (rev 195707)
</span><span class="lines">@@ -1,3 +1,22 @@
</span><ins>+2016-01-27 Benjamin Poulain <bpoulain@apple.com>
+
+ [JSC] adjustFrameAndStackInOSRExitCompilerThunk() can trash values in FTL
+ https://bugs.webkit.org/show_bug.cgi?id=153536
+
+ Reviewed by Saam Barati.
+
+ Workaround to get B3 working on ARM.
+
+ * dfg/DFGOSRExitCompilerCommon.h:
+ (JSC::DFG::adjustFrameAndStackInOSRExitCompilerThunk):
+ The code was using the scratch registers in a few places.
+
+ I initially tried to make is not use scratch registers anywhere
+ but that looked super fragile.
+
+ Instead, I just preserve the scratch registers. That's easy and
+ it should be relatively cheap compared to everything done on OSR Exits.
+
</ins><span class="cx"> 2016-01-27 Konstantin Tokarev <annulen@yandex.ru>
</span><span class="cx">
</span><span class="cx"> [mips] Use reinterpret_cast_ptr to suppress alignment warnings.
</span></span></pre></div>
<a id="trunkSourceJavaScriptCoredfgDFGOSRExitCompilerCommonh"></a>
<div class="modfile"><h4>Modified: trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompilerCommon.h (195706 => 195707)</h4>
<pre class="diff"><span>
<span class="info">--- trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompilerCommon.h 2016-01-28 00:18:37 UTC (rev 195706)
+++ trunk/Source/JavaScriptCore/dfg/DFGOSRExitCompilerCommon.h 2016-01-28 00:29:09 UTC (rev 195707)
</span><span class="lines">@@ -33,6 +33,7 @@
</span><span class="cx"> #include "DFGCommonData.h"
</span><span class="cx"> #include "DFGJITCode.h"
</span><span class="cx"> #include "FTLJITCode.h"
</span><ins>+#include "RegisterSet.h"
</ins><span class="cx">
</span><span class="cx"> namespace JSC { namespace DFG {
</span><span class="cx">
</span><span class="lines">@@ -44,22 +45,40 @@
</span><span class="cx"> void adjustFrameAndStackInOSRExitCompilerThunk(MacroAssembler& jit, VM* vm, JITCode::JITType jitType)
</span><span class="cx"> {
</span><span class="cx"> ASSERT(jitType == JITCode::DFGJIT || jitType == JITCode::FTLJIT);
</span><del>- size_t scratchSize = sizeof(void*);
</del><ins>+
</ins><span class="cx"> bool isFTLOSRExit = jitType == JITCode::FTLJIT;
</span><ins>+ RegisterSet registersToPreserve;
+ registersToPreserve.set(GPRInfo::regT0);
+ if (isFTLOSRExit) {
+ // FTL can use the scratch registers for values. The code below uses
+ // the scratch registers. We need to preserve them before doing anything.
+ registersToPreserve.merge(RegisterSet::macroScratchRegisters());
+ }
+
+ size_t scratchSize = sizeof(void*) * registersToPreserve.numberOfSetGPRs();
</ins><span class="cx"> if (isFTLOSRExit)
</span><span class="cx"> scratchSize += sizeof(void*);
</span><span class="cx">
</span><span class="cx"> ScratchBuffer* scratchBuffer = vm->scratchBufferForSize(scratchSize);
</span><span class="cx"> char* buffer = static_cast<char*>(scratchBuffer->dataBuffer());
</span><del>- jit.storePtr(GPRInfo::regT0, buffer);
</del><span class="cx">
</span><ins>+ jit.pushToSave(GPRInfo::regT1);
+ jit.move(MacroAssembler::TrustedImmPtr(buffer), GPRInfo::regT1);
+
+ unsigned storeOffset = 0;
+ registersToPreserve.forEach([&](Reg reg) {
+ jit.storePtr(reg.gpr(), MacroAssembler::Address(GPRInfo::regT1, storeOffset));
+ storeOffset += sizeof(void*);
+ });
+
</ins><span class="cx"> if (isFTLOSRExit) {
</span><span class="cx"> // FTL OSRExits are entered via the code FTLExitThunkGenerator emits which does
</span><span class="cx"> // pushToSaveImmediateWithoutTouchRegisters with the OSR exit index. We need to load
</span><span class="cx"> // that top value and then push it back when we reset our SP.
</span><del>- jit.peek(GPRInfo::regT0);
- jit.storePtr(GPRInfo::regT0, buffer + sizeof(void*));
</del><ins>+ jit.loadPtr(MacroAssembler::Address(MacroAssembler::stackPointerRegister, MacroAssembler::pushToSaveByteOffset()), GPRInfo::regT0);
+ jit.storePtr(GPRInfo::regT0, MacroAssembler::Address(GPRInfo::regT1, registersToPreserve.numberOfSetGPRs() * sizeof(void*)));
</ins><span class="cx"> }
</span><ins>+ jit.popToRestore(GPRInfo::regT1);
</ins><span class="cx">
</span><span class="cx"> // We need to reset FP in the case of an exception.
</span><span class="cx"> jit.loadPtr(vm->addressOfCallFrameForCatch(), GPRInfo::regT0);
</span><span class="lines">@@ -85,14 +104,26 @@
</span><span class="cx"> jit.move(GPRInfo::regT0, MacroAssembler::stackPointerRegister);
</span><span class="cx">
</span><span class="cx"> if (isFTLOSRExit) {
</span><ins>+ // Leave space for saving the OSR Exit Index.
+ jit.subPtr(MacroAssembler::TrustedImm32(MacroAssembler::pushToSaveByteOffset()), MacroAssembler::stackPointerRegister);
+ }
+ jit.pushToSave(GPRInfo::regT1);
+
+ jit.move(MacroAssembler::TrustedImmPtr(buffer), GPRInfo::regT1);
+ if (isFTLOSRExit) {
</ins><span class="cx"> // FTL OSRExits are entered via FTLExitThunkGenerator code with does
</span><span class="cx"> // pushToSaveImmediateWithoutTouchRegisters. We need to load that top
</span><span class="cx"> // register and then store it back when we have our SP back to a safe value.
</span><del>- jit.loadPtr(buffer + sizeof(void*), GPRInfo::regT0);
- jit.pushToSave(GPRInfo::regT0);
</del><ins>+ jit.loadPtr(MacroAssembler::Address(GPRInfo::regT1, registersToPreserve.numberOfSetGPRs() * sizeof(void*)), GPRInfo::regT0);
+ jit.storePtr(GPRInfo::regT0, MacroAssembler::Address(MacroAssembler::stackPointerRegister, MacroAssembler::pushToSaveByteOffset()));
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- jit.loadPtr(buffer, GPRInfo::regT0);
</del><ins>+ unsigned loadOffset = 0;
+ registersToPreserve.forEach([&](Reg reg) {
+ jit.loadPtr(MacroAssembler::Address(GPRInfo::regT1, loadOffset), reg.gpr());
+ loadOffset += sizeof(void*);
+ });
+ jit.popToRestore(GPRInfo::regT1);
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx">
</span></span></pre>
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