Merge r241862 - [JSC] Remove WatchpointSet creation for SymbolTable e…

…ntries if VM::canUseJIT() returns false https://bugs.webkit.org/show_bug.cgi?id=194891 Reviewed by Geoffrey Garen. WatchpointSet in SymbolTable is used to fold the value into a constant in JIT tiers. And it is not useful under the non-JIT mode. This patch avoids creation of WatchpointSet in SymbolTable if VM::canUseJIT() returns false. * llint/LowLevelInterpreter32_64.asm: * llint/LowLevelInterpreter64.asm: * runtime/SymbolTable.cpp: (JSC::SymbolTableEntry::addWatchpoint): Deleted. * runtime/SymbolTable.h: (JSC::SymbolTableEntry::isWatchable const): (JSC::SymbolTableEntry::watchpointSet):
WebKit · Mar 5, 2019 · 1b37245 · 1b37245
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commit 1b37245
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Showing 5 changed files with 28 additions and 10 deletions.
diff --git a/Source/JavaScriptCore/ChangeLog b/Source/JavaScriptCore/ChangeLog
@@ -1,3 +1,22 @@
+2019-02-20  Yusuke Suzuki  <ysuzuki@apple.com>
+
+        [JSC] Remove WatchpointSet creation for SymbolTable entries if VM::canUseJIT() returns false
+        https://bugs.webkit.org/show_bug.cgi?id=194891
+
+        Reviewed by Geoffrey Garen.
+
+        WatchpointSet in SymbolTable is used to fold the value into a constant in JIT tiers. And it is
+        not useful under the non-JIT mode. This patch avoids creation of WatchpointSet in SymbolTable
+        if VM::canUseJIT() returns false.
+
+        * llint/LowLevelInterpreter32_64.asm:
+        * llint/LowLevelInterpreter64.asm:
+        * runtime/SymbolTable.cpp:
+        (JSC::SymbolTableEntry::addWatchpoint): Deleted.
+        * runtime/SymbolTable.h:
+        (JSC::SymbolTableEntry::isWatchable const):
+        (JSC::SymbolTableEntry::watchpointSet):
+
 2019-02-20  Mark Lam  <mark.lam@apple.com>
 
         Add code to validate expected GC activity modelled by doesGC() against what the runtime encounters.

diff --git a/Source/JavaScriptCore/llint/LowLevelInterpreter32_64.asm b/Source/JavaScriptCore/llint/LowLevelInterpreter32_64.asm
@@ -2274,7 +2274,9 @@ llintOpWithMetadata(op_put_to_scope, OpPutToScope, macro (size, get, dispatch, m
         get(m_value, t0)
         loadConstantOrVariable(size, t0, t1, t2)
         loadp OpPutToScope::Metadata::m_watchpointSet[t5], t3
+        btpz t3, .noVariableWatchpointSet
         notifyWrite(t3, .pDynamic)
+    .noVariableWatchpointSet:
         loadp OpPutToScope::Metadata::m_operand[t5], t0
         storei t1, TagOffset[t0]
         storei t2, PayloadOffset[t0]

diff --git a/Source/JavaScriptCore/llint/LowLevelInterpreter64.asm b/Source/JavaScriptCore/llint/LowLevelInterpreter64.asm
@@ -2310,8 +2310,10 @@ llintOpWithMetadata(op_put_to_scope, OpPutToScope, macro (size, get, dispatch, m
         get(m_value, t0)
         loadConstantOrVariable(size, t0, t1)
         loadp OpPutToScope::Metadata::m_watchpointSet[t5], t2
-        loadp OpPutToScope::Metadata::m_operand[t5], t0
+        btpz t2, .noVariableWatchpointSet
         notifyWrite(t2, .pDynamic)
+    .noVariableWatchpointSet:
+        loadp OpPutToScope::Metadata::m_operand[t5], t0
         storeq t1, [t0]
     end
 

diff --git a/Source/JavaScriptCore/runtime/SymbolTable.cpp b/Source/JavaScriptCore/runtime/SymbolTable.cpp
@@ -70,11 +70,6 @@ void SymbolTableEntry::prepareToWatch()
     entry->m_watchpoints = adoptRef(new WatchpointSet(ClearWatchpoint));
 }
 
-void SymbolTableEntry::addWatchpoint(Watchpoint* watchpoint)
-{
-    fatEntry()->m_watchpoints->add(watchpoint);
-}
-
 SymbolTableEntry::FatEntry* SymbolTableEntry::inflateSlow()
 {
     FatEntry* entry = new FatEntry(m_bits);

diff --git a/Source/JavaScriptCore/runtime/SymbolTable.h b/Source/JavaScriptCore/runtime/SymbolTable.h
@@ -229,7 +229,7 @@ struct SymbolTableEntry {
 
     bool isWatchable() const
     {
-        return (m_bits & KindBitsMask) == ScopeKindBits;
+        return (m_bits & KindBitsMask) == ScopeKindBits && VM::canUseJIT();
     }
 
     // Asserts if the offset is anything but a scope offset. This structures the assertions
@@ -291,8 +291,6 @@ struct SymbolTableEntry {
 
     void prepareToWatch();
 
-    void addWatchpoint(Watchpoint*);
-
     // This watchpoint set is initialized clear, and goes through the following state transitions:
     // 
     // First write to this var, in any scope that has this symbol table: Clear->IsWatched.
@@ -312,10 +310,12 @@ struct SymbolTableEntry {
     // initializes that var in just one of them. This means that a compilation could constant-fold to one
     // of the scopes that still has an undefined value for this variable. That's fine, because at that
     // point any write to any of the instances of that variable would fire the watchpoint.
+    //
+    // Note that watchpointSet() returns nullptr if JIT is disabled.
     WatchpointSet* watchpointSet()
     {
         if (!isFat())
-            return 0;
+            return nullptr;
         return fatEntry()->m_watchpoints.get();
     }