Changeset 261731 in webkit for trunk/Source/JavaScriptCore/jsc.cpp

Timestamp:

May 14, 2020, 11:55:08 PM (5 years ago)

Author:

[email protected]

Message:

GetByVal and PutByVal runtime operations shouldn't fall off a performance cliff when the property is an integer boxed as a double
​https://bugs.webkit.org/show_bug.cgi?id=211935

Reviewed by Yusuke Suzuki and Mark Lam.

JSTests:

• microbenchmarks/get-and-put-by-val-double-index-dont-fall-off-a-cliff.js: Added.

(test):

Source/JavaScriptCore:

There were parts in the runtime for get_by_val that weren't properly handling
ints boxed as doubles along the fast path. This could lead to terrible
performance as we could go from double -> string -> int while converting the
subscript into a property to access.

This patch fixes that, and removes the duplicate code we had throughout the
codebase that does this conversion. I'm adding a new functions tryGetAsUint32Index
and tryGetAsInt32 which will handle the double to int conversion.

This is a 10x speedup on the microbenchmark get-and-put-by-val-double-index-dont-fall-off-a-cliff.js

• dfg/DFGOperations.cpp:

(JSC::DFG::putByValInternal):

• jit/JITOperations.cpp:

(JSC::getByVal):

• jsc.cpp:

(functionAsDoubleNumber):

• llint/LLIntSlowPaths.cpp:

(JSC::LLInt::getByVal):
(JSC::LLInt::LLINT_SLOW_PATH_DECL):

• runtime/JSCJSValue.h:
• runtime/JSCJSValueInlines.h:

(JSC::JSValue::tryGetAsUint32Index):
(JSC::JSValue::tryGetAsInt32):

File:

• trunk/Source/JavaScriptCore/jsc.cpp (modified) (3 diffs)

trunk/Source/JavaScriptCore/jsc.cpp

@@ -374 +374 @@
 
 static EncodedJSValue JSC_HOST_CALL functionSetUnhandledRejectionCallback(JSGlobalObject*, CallFrame*);
+static EncodedJSValue JSC_HOST_CALL functionAsDoubleNumber(JSGlobalObject*, CallFrame*);
 
 struct Script {
@@ -642 +643 @@
 
         addFunction(vm, "setUnhandledRejectionCallback", functionSetUnhandledRejectionCallback, 1);
+
+        addFunction(vm, "asDoubleNumber", functionAsDoubleNumber, 1);
     }
     
@@ -2493 +2496 @@
 }
 
+EncodedJSValue JSC_HOST_CALL functionAsDoubleNumber(JSGlobalObject* globalObject, CallFrame* callFrame)
+{
+    VM& vm = globalObject->vm();
+    auto scope = DECLARE_THROW_SCOPE(vm);
+    double num = callFrame->argument(0).toNumber(globalObject);
+    RETURN_IF_EXCEPTION(scope, encodedJSValue());
+    return JSValue::encode(jsDoubleNumber(num));
+}
+
 // Use SEH for Release builds only to get rid of the crash report dialog
 // (luckily the same tests fail in Release and Debug builds so far). Need to