@@ -59,7 +59,7 @@ function testJEQF(a, b)
 }
 noInline(testJEQF);
 
-for (var i = 0; i < 1e4; ++i) {
+for (var i = 0; i < testLoopCount; ++i) {
     shouldBe(testJNEQ(0, 42), 30);
     shouldBe(testJEQ(0, 42), 42);
     shouldBe(testJNEQB(0, 0), 1);
 
@@ -973,6 +973,9 @@ set(JavaScriptCore_PRIVATE_FRAMEWORK_HEADERS
     llint/LLIntPCRanges.h
     llint/LLIntThunks.h
 
+    lol/LOLJIT.h
+    lol/LOLRegisterAllocator.h
+
     parser/Lexer.h
     parser/ParserArena.h
     parser/ParserError.h
 
@@ -1016,6 +1016,7 @@
 		530A66C31FA3E78B0026A545 /* UnifiedSource144.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 530A66AD1FA3E7770026A545 /* UnifiedSource144.cpp */; };
 		530A66C41FA3E78B0026A545 /* UnifiedSource145.cpp in Sources */ = {isa = PBXBuildFile; fileRef = 530A66B01FA3E77A0026A545 /* UnifiedSource145.cpp */; };
 		530A66CD1FB1346D0026A545 /* SuperSamplerBytecodeScope.h in Headers */ = {isa = PBXBuildFile; fileRef = 530A66CC1FB1346D0026A545 /* SuperSamplerBytecodeScope.h */; };
+		530E4FAF2E3455E000479AEE /* LOLJIT.h in Headers */ = {isa = PBXBuildFile; fileRef = 530E4FAB2E34554A00479AEE /* LOLJIT.h */; };
 		530F0A982AE0607B00A0EEC0 /* LazyValueProfile.h in Headers */ = {isa = PBXBuildFile; fileRef = 530F0A962AE0606900A0EEC0 /* LazyValueProfile.h */; settings = {ATTRIBUTES = (Private, ); }; };
 		530FB3021E7A0B6E003C19DD /* WasmWorklist.h in Headers */ = {isa = PBXBuildFile; fileRef = 530FB3011E7A0B6E003C19DD /* WasmWorklist.h */; };
 		530FDE7521FAB00600059D65 /* testIncludes.m in Sources */ = {isa = PBXBuildFile; fileRef = 530FDE7321FAAFC600059D65 /* testIncludes.m */; };
@@ -4252,6 +4253,8 @@
 		530A66B71FA3E77D0026A545 /* UnifiedSource143.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; name = UnifiedSource143.cpp; path = "DerivedSources/JavaScriptCore/unified-sources/UnifiedSource143.cpp"; sourceTree = BUILT_PRODUCTS_DIR; };
 		530A66B81FA3E77E0026A545 /* UnifiedSource4-nonARC.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = "UnifiedSource4-nonARC.mm"; path = "DerivedSources/JavaScriptCore/unified-sources/UnifiedSource4-nonARC.mm"; sourceTree = BUILT_PRODUCTS_DIR; };
 		530A66CC1FB1346D0026A545 /* SuperSamplerBytecodeScope.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = SuperSamplerBytecodeScope.h; sourceTree = "<group>"; };
+		530E4FAB2E34554A00479AEE /* LOLJIT.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; name = LOLJIT.h; path = lol/LOLJIT.h; sourceTree = "<group>"; };
+		530E4FAC2E34554A00479AEE /* LOLJIT.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; name = LOLJIT.cpp; path = lol/LOLJIT.cpp; sourceTree = "<group>"; };
 		530F0A962AE0606900A0EEC0 /* LazyValueProfile.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = LazyValueProfile.h; sourceTree = "<group>"; };
 		530F0A972AE0606900A0EEC0 /* LazyValueProfile.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = LazyValueProfile.cpp; sourceTree = "<group>"; };
 		530FB3011E7A0B6E003C19DD /* WasmWorklist.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = WasmWorklist.h; sourceTree = "<group>"; };
@@ -6523,6 +6526,8 @@
 				45E12D8806A49B0F00E9DF84 /* jsc.cpp */,
 				A7C225CC139981F100FF1662 /* KeywordLookupGenerator.py */,
 				79D7B0E121152FD200FE7C64 /* entitlements.plist */,
+				530E4FAB2E34554A00479AEE /* LOLJIT.h */,
+				530E4FAC2E34554A00479AEE /* LOLJIT.cpp */,
 				1432EBD70A34CAD400717B9F /* API */,
 				9688CB120ED12B4E001D649F /* assembler */,
 				0FEC84B21BDACD5E0080FF74 /* b3 */,
@@ -11868,6 +11873,7 @@
 				92B4EF902D71C3650068CB55 /* LLVMProfiling.h in Headers */,
 				0F75A061200D26180038E2CF /* LocalAllocator.h in Headers */,
 				0F75A060200D260B0038E2CF /* LocalAllocatorInlines.h in Headers */,
+				530E4FAF2E3455E000479AEE /* LOLJIT.h in Headers */,
 				BC18C4370E16F5CD00B34460 /* Lookup.h in Headers */,
 				0F4680CD14BBB17D00BFE272 /* LowLevelInterpreter.h in Headers */,
 				981ED82328234D91BAECCADE /* MachineContext.h in Headers */,
 
@@ -693,6 +693,8 @@ jit/ThunkGenerators.cpp
 jit/JITTZoneImpls.cpp
 jit/Width.cpp
 
+lol/LOLJIT.cpp
+
 llint/InPlaceInterpreter.cpp
 llint/LLIntCLoop.cpp
 llint/LLIntData.cpp
 
@@ -38,7 +38,7 @@ template<typename T> struct OperandValueTraits;
 
 constexpr unsigned maxNumCheckpointTmps = 4;
 
-// A OperandKind::Tmp is one that exists for exiting to a checkpoint but does not exist between bytecodes.
+// An OperandKind::Tmp is one that exists for exiting to a checkpoint but does not exist between bytecodes.
 enum class OperandKind : uint32_t { Argument, Local, Tmp }; // Keep bit-width in sync with Operand::operandKindBits' definition.
 static constexpr OperandKind lastOperandKind = OperandKind::Tmp;
 
 
@@ -88,7 +88,7 @@ def self.license(file, template, dependencies)
 
         comment = if template.multiline_comment.nil? then template.line_comment else template.multiline_comment[1] end
         write(file, $LICENSE.strip.split("\n").map { |line| "#{comment} #{line}" }.join("\n"), "\n\n")
-        write(file, comment, " Autogenerated, do not modify.\n")
+        write(file, comment, " Autogenerated by generator/main.rb, do not modify.\n")
 
         unless template.multiline_comment.nil?
             write(file, template.multiline_comment[2], "\n")
 
@@ -1507,9 +1507,13 @@ class AssemblyHelpers : public MacroAssembler {
         jitAssertIsJSDouble(gpr);
         return unboxDoubleWithoutAssertions(gpr, resultGPR, fpr, mode);
     }
+    void unboxDouble(JSValueRegs regs, GPRReg resultGPR, FPRReg fpr)
+    {
+        unboxDouble(regs.payloadGPR(), resultGPR, fpr);
+    }
     void unboxDouble(JSValueRegs regs, FPRReg fpr)
     {
-        unboxDouble(regs.tagGPR(), regs.payloadGPR(), fpr);
+        unboxDouble(regs.payloadGPR(), regs.payloadGPR(), fpr);
     }
     void boxDouble(FPRReg fpr, JSValueRegs regs, TagRegistersMode mode = HaveTagRegisters)
     {
 
@@ -25,6 +25,7 @@
 
 #include "config.h"
 #include "BaselineJITPlan.h"
+#include "LOLJIT.h"
 
 #include "JITSafepoint.h"
 
@@ -47,9 +48,19 @@ auto BaselineJITPlan::compileInThreadImpl(JITCompilationEffort effort) -> Compil
         Safepoint safepoint(*this, result);
         safepoint.begin(false);
 
-        JIT jit(*m_vm, *this, m_codeBlock);
-        auto jitCode = jit.compileAndLinkWithoutFinalizing(effort);
-        m_jitCode = WTFMove(jitCode);
+        if (Options::useLOLJIT()) {
+#if USE(JSVALUE64)
+            LOL::LOLJIT jit(*m_vm, *this, m_codeBlock);
+            auto jitCode = jit.compileAndLinkWithoutFinalizing(effort);
+            m_jitCode = WTFMove(jitCode);
+#else
+            RELEASE_ASSERT_NOT_REACHED();
+#endif
+        } else {
+            JIT jit(*m_vm, *this, m_codeBlock);
+            auto jitCode = jit.compileAndLinkWithoutFinalizing(effort);
+            m_jitCode = WTFMove(jitCode);
+        }
     }
     if (result.didGetCancelled())
         return CancelPath;
 
@@ -614,8 +614,8 @@ void JIT::privateCompileSlowCases()
         if (JITInternal::verbose)
             dataLog("At ", firstTo, " slow: ", iter - m_slowCases.begin(), "\n");
 
-        RELEASE_ASSERT_WITH_MESSAGE(iter == m_slowCases.end() || firstTo.offset() != iter->to.offset(), "Not enough jumps linked in slow case codegen.");
-        RELEASE_ASSERT_WITH_MESSAGE(firstTo.offset() == (iter - 1)->to.offset(), "Too many jumps linked in slow case codegen.");
+        RELEASE_ASSERT_WITH_MESSAGE(iter == m_slowCases.end() || firstTo.offset() != iter->to.offset(), "Not enough jumps linked in slow case codegen while handling %s.", toCString(currentInstruction->opcodeID()).data());
+        RELEASE_ASSERT_WITH_MESSAGE(firstTo.offset() == (iter - 1)->to.offset(), "Too many jumps linked in slow case codegen while handling %s.", toCString(currentInstruction->opcodeID()).data());
 
         jump().linkTo(fastPathResumePoint(), this);
         ++bytecodeCountHavingSlowCase;
 
@@ -61,6 +61,10 @@ namespace JSC {
     class StructureChain;
     class StructureStubInfo;
 
+    namespace LOL {
+        class LOLJIT;
+    }
+
     template<typename> struct BaseInstruction;
     struct JSOpcodeTraits;
     using JSInstruction = BaseInstruction<JSOpcodeTraits>;
@@ -118,7 +122,7 @@ namespace JSC {
     struct SlowCaseEntry {
         MacroAssembler::Jump from;
         BytecodeIndex to;
-        
+
         SlowCaseEntry(MacroAssembler::Jump f, BytecodeIndex t)
             : from(f)
             , to(t)
@@ -153,12 +157,13 @@ namespace JSC {
         BaselineUnlinkedCallLinkInfo* unlinkedCallLinkInfo;
     };
 
-    class JIT final : public JSInterfaceJIT {
+    class JIT : public JSInterfaceJIT {
         WTF_MAKE_TZONE_NON_HEAP_ALLOCATABLE(JIT);
 
         friend class JITSlowPathCall;
         friend class JITStubCall;
         friend class JITThunks;
+        friend class LOL::LOLJIT;
 
         using MacroAssembler::Jump;
         using MacroAssembler::JumpList;
@@ -335,6 +340,7 @@ namespace JSC {
         void emitJumpSlowCaseIfNotInt(RegisterID);
 #endif
 
+        void emitJumpSlowCaseIfNotInt(JSValueRegs, JSValueRegs, RegisterID scratch);
         void emitJumpSlowCaseIfNotInt(JSValueRegs);
 
         void emitJumpSlowCaseIfNotJSCell(JSValueRegs);
@@ -671,12 +677,12 @@ namespace JSC {
                 iter->from.link(this);
             ++iter;
         }
-        void linkAllSlowCasesForBytecodeIndex(Vector<SlowCaseEntry>& slowCases,
+        void linkAllSlowCasesUpToBytecodeIndex(Vector<SlowCaseEntry>& slowCases,
             Vector<SlowCaseEntry>::iterator&, BytecodeIndex bytecodeOffset);
 
         void linkAllSlowCases(Vector<SlowCaseEntry>::iterator& iter)
         {
-            linkAllSlowCasesForBytecodeIndex(m_slowCases, iter, m_bytecodeIndex);
+            linkAllSlowCasesUpToBytecodeIndex(m_slowCases, iter, m_bytecodeIndex);
         }
 
         bool hasAnySlowCases(Vector<SlowCaseEntry>& slowCases, Vector<SlowCaseEntry>::iterator&, BytecodeIndex bytecodeOffset);
Original file line number	Diff line number	Diff line change
`@@ -59,7 +59,7 @@ function testJEQF(a, b)`
`59`	`59`	`}`
`60`	`60`	`noInline(testJEQF);`
`61`	`61`
`62`		`-for (var i = 0; i < 1e4; ++i) {`
	`62`	`+for (var i = 0; i < testLoopCount; ++i) {`
`63`	`63`	`shouldBe(testJNEQ(0, 42), 30);`
`64`	`64`	`shouldBe(testJEQ(0, 42), 42);`
`65`	`65`	`shouldBe(testJNEQB(0, 0), 1);`
Original file line number	Diff line number	Diff line change
`@@ -1507,9 +1507,13 @@ class AssemblyHelpers : public MacroAssembler {`
`1507`	`1507`	`jitAssertIsJSDouble(gpr);`
`1508`	`1508`	`return unboxDoubleWithoutAssertions(gpr, resultGPR, fpr, mode);`
`1509`	`1509`	`}`
	`1510`	`+ void unboxDouble(JSValueRegs regs, GPRReg resultGPR, FPRReg fpr)`
	`1511`	`+ {`
	`1512`	`+ unboxDouble(regs.payloadGPR(), resultGPR, fpr);`
	`1513`	`+ }`
`1510`	`1514`	`void unboxDouble(JSValueRegs regs, FPRReg fpr)`
`1511`	`1515`	`{`
`1512`		`- unboxDouble(regs.tagGPR(), regs.payloadGPR(), fpr);`
	`1516`	`+ unboxDouble(regs.payloadGPR(), regs.payloadGPR(), fpr);`
`1513`	`1517`	`}`
`1514`	`1518`	`void boxDouble(FPRReg fpr, JSValueRegs regs, TagRegistersMode mode = HaveTagRegisters)`
`1515`	`1519`	`{`