Changeset 277117 in webkit

Timestamp:

May 6, 2021 1:54:16 PM (3 years ago)

Author:

fpizlo@apple.com

Message:

Reduce use of dmb ish on ARM64
​https://bugs.webkit.org/show_bug.cgi?id=225465

Reviewed by Keith Miller.
Source/JavaScriptCore:

We use loadLoadFence a lot, often in situations like:

Foo* ptr = loadStuff;
loadLoadFence();
use ptr

On ARM64, we don't need a dmb ish here. This introduces a dependentLoadLoadFence() for these
cases; it's just a compiler fence on ARM64 and Intel.

We also used loadLoadFence in some places where I couldn't think of any good reason for the
fence other than paranoia. I got rid of those.

• bytecode/CallLinkStatus.cpp:

(JSC::CallLinkStatus::computeFromCallLinkInfo):

• bytecode/CodeBlock.h:

(JSC::CodeBlock::jitType const):

• bytecode/ObjectAllocationProfile.h:

(JSC::ObjectAllocationProfileBase::structure):
(JSC::ObjectAllocationProfileWithPrototype::prototype):

• bytecode/Watchpoint.h:

(JSC::WatchpointSet::state const):
(JSC::InlineWatchpointSet::state const):

• dfg/DFGByteCodeParser.cpp:

(JSC::DFG::ByteCodeParser::parseBlock):
(JSC::DFG::ByteCodeParser::handlePutByVal):

• dfg/DFGSpeculativeJIT.cpp:

(JSC::DFG::SpeculativeJIT::compileGetByValOnString):

• ftl/FTLLowerDFGToB3.cpp:

(JSC::FTL::DFG::LowerDFGToB3::compileStringCharAt):

• runtime/GetterSetter.h:
• runtime/InferredValue.h:

(JSC::InferredValue::state const):

• runtime/Structure.h:

(JSC::Structure::tryRareData):

• runtime/StructureInlines.h:

(JSC::Structure::propertyReplacementWatchpointSet):

Source/WTF:

• wtf/Atomics.h:

(WTF::dependentLoadLoadFence):

Location:

trunk/Source

Files:

• JavaScriptCore/ChangeLog (modified) (1 diff)
• JavaScriptCore/bytecode/CallLinkStatus.cpp (modified) (1 diff)
• JavaScriptCore/bytecode/CodeBlock.h (modified) (1 diff)
• JavaScriptCore/bytecode/ObjectAllocationProfile.h (modified) (2 diffs)
• JavaScriptCore/bytecode/Watchpoint.h (modified) (2 diffs)
• JavaScriptCore/dfg/DFGByteCodeParser.cpp (modified) (1 diff)
• JavaScriptCore/dfg/DFGSpeculativeJIT.cpp (modified) (1 diff)
• JavaScriptCore/ftl/FTLLowerDFGToB3.cpp (modified) (1 diff)
• JavaScriptCore/runtime/GetterSetter.h (modified) (1 diff)
• JavaScriptCore/runtime/InferredValue.h (modified) (1 diff)
• JavaScriptCore/runtime/Structure.h (modified) (2 diffs)
• JavaScriptCore/runtime/StructureInlines.h (modified) (1 diff)
• WTF/ChangeLog (modified) (1 diff)
• WTF/wtf/Atomics.h (modified) (1 diff)

trunk/Source/JavaScriptCore/ChangeLog

@@ +1 @@
+2021-05-06  Filip Pizlo  <fpizlo@apple.com>
+
+        Reduce use of dmb ish on ARM64
+        https://bugs.webkit.org/show_bug.cgi?id=225465
+
+        Reviewed by Keith Miller.
+        
+        We use loadLoadFence a lot, often in situations like:
+        
+        Foo* ptr = loadStuff;
+        loadLoadFence();
+        use ptr
+        
+        On ARM64, we don't need a dmb ish here.  This introduces a dependentLoadLoadFence() for these
+        cases; it's just a compiler fence on ARM64 and Intel.
+
+        We also used loadLoadFence in some places where I couldn't think of any good reason for the
+        fence other than paranoia. I got rid of those.
+
+        * bytecode/CallLinkStatus.cpp:
+        (JSC::CallLinkStatus::computeFromCallLinkInfo):
+        * bytecode/CodeBlock.h:
+        (JSC::CodeBlock::jitType const):
+        * bytecode/ObjectAllocationProfile.h:
+        (JSC::ObjectAllocationProfileBase::structure):
+        (JSC::ObjectAllocationProfileWithPrototype::prototype):
+        * bytecode/Watchpoint.h:
+        (JSC::WatchpointSet::state const):
+        (JSC::InlineWatchpointSet::state const):
+        * dfg/DFGByteCodeParser.cpp:
+        (JSC::DFG::ByteCodeParser::parseBlock):
+        (JSC::DFG::ByteCodeParser::handlePutByVal):
+        * dfg/DFGSpeculativeJIT.cpp:
+        (JSC::DFG::SpeculativeJIT::compileGetByValOnString):
+        * ftl/FTLLowerDFGToB3.cpp:
+        (JSC::FTL::DFG::LowerDFGToB3::compileStringCharAt):
+        * runtime/GetterSetter.h:
+        * runtime/InferredValue.h:
+        (JSC::InferredValue::state const):
+        * runtime/Structure.h:
+        (JSC::Structure::tryRareData):
+        * runtime/StructureInlines.h:
+        (JSC::Structure::propertyReplacementWatchpointSet):
+
 2021-05-06  Filip Pizlo  <fpizlo@apple.com>
 

trunk/Source/JavaScriptCore/bytecode/CallLinkStatus.cpp

@@ -194 +194 @@
     // fencing in place to make sure that we see the variants list after construction.
     if (PolymorphicCallStubRoutine* stub = callLinkInfo.stub()) {
-        WTF::loadLoadFence();
+        WTF::dependentLoadLoadFence();
         
         if (!stub->hasEdges()) {

trunk/Source/JavaScriptCore/bytecode/CodeBlock.h

@@ -435 +435 @@
     {
         JITCode* jitCode = m_jitCode.get();
-        WTF::loadLoadFence();
         JITType result = JITCode::jitTypeFor(jitCode);
-        WTF::loadLoadFence(); // This probably isn't needed. Oh well, paranoia is good.
         return result;
     }

trunk/Source/JavaScriptCore/bytecode/ObjectAllocationProfile.h

@@ -53 +53 @@
         Structure* structure = m_structure.get();
         // Ensure that if we see the structure, it has been properly created
-        WTF::loadLoadFence();
+        WTF::dependentLoadLoadFence();
         return structure;
     }
@@ -101 +101 @@
     {
         JSObject* prototype = m_prototype.get();
-        WTF::loadLoadFence();
+        WTF::dependentLoadLoadFence();
         return prototype;
     }

trunk/Source/JavaScriptCore/bytecode/Watchpoint.h

@@ -209 +209 @@
     WatchpointState state() const
     {
-        WTF::loadLoadFence();
         WatchpointState result = static_cast<WatchpointState>(m_state);
-        WTF::loadLoadFence();
         return result;
     }
@@ -362 +360 @@
     WatchpointState state() const
     {
-        WTF::loadLoadFence();
         uintptr_t data = m_data;
-        WTF::loadLoadFence();
         if (isFat(data))
             return fat(data)->state();

trunk/Source/JavaScriptCore/dfg/DFGByteCodeParser.cpp

@@ -5656 +5656 @@
             // Unfortunately, we can't allocate a new JSImmutableButterfly if the profile tells us new information because we
             // cannot allocate from compilation threads.
-            WTF::loadLoadFence();
             FrozenValue* frozen = get(VirtualRegister(bytecode.m_immutableButterfly))->constant();
-            WTF::loadLoadFence();
+            WTF::dependentLoadLoadFence();
             JSImmutableButterfly* immutableButterfly = frozen->cast<JSImmutableButterfly*>();
             NewArrayBufferData data { };

trunk/Source/JavaScriptCore/dfg/DFGSpeculativeJIT.cpp

@@ -2405 +2405 @@
         Structure* stringPrototypeStructure = globalObject->stringPrototype()->structure(vm);
         Structure* objectPrototypeStructure = globalObject->objectPrototype()->structure(vm);
-        WTF::loadLoadFence();
+        WTF::dependentLoadLoadFence();
 
         if (globalObject->stringPrototypeChainIsSane()) {

trunk/Source/JavaScriptCore/ftl/FTLLowerDFGToB3.cpp

@@ -8494 +8494 @@
             Structure* stringPrototypeStructure = globalObject->stringPrototype()->structure(vm());
             Structure* objectPrototypeStructure = globalObject->objectPrototype()->structure(vm());
-            WTF::loadLoadFence();
+            WTF::dependentLoadLoadFence();
 
             if (globalObject->stringPrototypeChainIsSane()) {

trunk/Source/JavaScriptCore/runtime/GetterSetter.h

@@ -90 +90 @@
     {
         JSObject* result = getter();
-        WTF::loadLoadFence();
+        WTF::dependentLoadLoadFence();
         return result;
     }

trunk/Source/JavaScriptCore/runtime/InferredValue.h

@@ -82 +82 @@
     WatchpointState state() const
     {
-        WTF::loadLoadFence();
         uintptr_t data = m_data;
-        WTF::loadLoadFence();
         if (isFat(data))
             return fat(data)->state();

trunk/Source/JavaScriptCore/runtime/Structure.h

@@ -44 +44 @@
 #include "Watchpoint.h"
 #include "WriteBarrierInlines.h"
+#include <wtf/Atomics.h>
 #include <wtf/PrintStream.h>
 
@@ -339 +340 @@
     }
 
+    StructureRareData* tryRareData()
+    {
+        JSCell* value = m_previousOrRareData.get();
+        WTF::dependentLoadLoadFence();
+        if (isRareData(value))
+            return static_cast<StructureRareData*>(value);
+        return nullptr;
+    }
+
     const StructureRareData* rareData() const
     {

trunk/Source/JavaScriptCore/runtime/StructureInlines.h

@@ -368 +368 @@
 {
     ConcurrentJSLocker locker(m_lock);
-    if (!hasRareData())
+    StructureRareData* rareData = tryRareData();
+    if (!rareData)
         return nullptr;
-    WTF::loadLoadFence();
-    StructureRareData::PropertyWatchpointMap* map = rareData()->m_replacementWatchpointSets.get();
+    StructureRareData::PropertyWatchpointMap* map = rareData->m_replacementWatchpointSets.get();
     if (!map)
         return nullptr;

trunk/Source/WTF/ChangeLog

@@ +1 @@
+2021-05-06  Filip Pizlo  <fpizlo@apple.com>
+
+        Reduce use of dmb ish on ARM64
+        https://bugs.webkit.org/show_bug.cgi?id=225465
+
+        Reviewed by Keith Miller.
+
+        * wtf/Atomics.h:
+        (WTF::dependentLoadLoadFence):
+
 2021-05-06  Per Arne Vollan  <pvollan@apple.com>
 

trunk/Source/WTF/wtf/Atomics.h

@@ -329 +329 @@
 #endif
 
+#if CPU(ARM64) || CPU(X86) || CPU(X86_64)
+// Use this fence if you want a fence between loads that are already depdendent.
+inline void dependentLoadLoadFence() { compilerFence(); }
+#else
+inline void dependentLoadLoadFence() { loadLoadFence(); }
+#endif
+
 typedef unsigned InternalDependencyType;