Pass VM instead of JSGlobalObject to function constructors.
Created attachment 212943 [details] Patch
Benchmark report for SunSpider on foie (MacBookPro10,1). VMs tested: "TipOfTree" at /Users/akling/Source/Safari/Reference-OpenSource/WebKitBuild/Release/jsc "MyChanges" at /Users/akling/Source/Safari/OpenSource/WebKitBuild/Release/jsc Collected 4 samples per benchmark/VM, with 4 VM invocations per benchmark. Emitted a call to gc() between sample measurements. Used 1 benchmark iteration per VM invocation for warm-up. Used the jsc-specific preciseTime() function to get microsecond-level timing. Reporting benchmark execution times with 95% confidence intervals in milliseconds. TipOfTree MyChanges 3d-cube 5.0504+-0.2404 ? 5.0685+-0.4292 ? 3d-morph 5.3848+-0.1364 ? 5.4618+-0.2715 ? might be 1.0143x slower 3d-raytrace 6.4196+-0.6557 6.3090+-0.3647 might be 1.0175x faster access-binary-trees 1.3939+-0.1756 1.3300+-0.0646 might be 1.0480x faster access-fannkuch 5.6747+-1.8268 5.0225+-0.1727 might be 1.1299x faster access-nbody 2.4979+-0.0869 ? 2.5365+-0.1272 ? might be 1.0155x slower access-nsieve 3.2899+-0.0775 3.2593+-0.1950 bitops-3bit-bits-in-byte 1.3797+-0.0327 ? 1.4056+-0.0422 ? might be 1.0188x slower bitops-bits-in-byte 1.8750+-0.1168 ? 1.9258+-0.2800 ? might be 1.0271x slower bitops-bitwise-and 1.9222+-0.0419 1.9171+-0.0297 bitops-nsieve-bits 3.0391+-0.2831 2.8948+-0.0700 might be 1.0498x faster controlflow-recursive 1.8852+-0.0740 1.8689+-0.0443 crypto-aes 3.6846+-0.3304 3.6338+-0.0604 might be 1.0140x faster crypto-md5 2.2400+-0.1685 2.1845+-0.0904 might be 1.0254x faster crypto-sha1 2.1714+-0.2661 ? 2.1838+-0.2136 ? date-format-tofte 7.3279+-0.2435 ? 7.6221+-1.3069 ? might be 1.0401x slower date-format-xparb 5.2873+-0.0333 ? 5.5544+-0.3916 ? might be 1.0505x slower math-cordic 2.9060+-0.4604 2.7918+-0.0209 might be 1.0409x faster math-partial-sums 5.4099+-0.2110 ? 5.8085+-0.6211 ? might be 1.0737x slower math-spectral-norm 1.7714+-0.1938 1.7349+-0.0814 might be 1.0210x faster regexp-dna 7.7466+-0.3649 ? 7.8943+-0.3119 ? might be 1.0191x slower string-base64 3.5917+-0.2942 ? 3.8972+-0.7940 ? might be 1.0851x slower string-fasta 11.7495+-0.4235 11.2756+-0.4031 might be 1.0420x faster string-tagcloud 9.7996+-0.7279 ? 10.4869+-0.7872 ? might be 1.0701x slower string-unpack-code 20.3339+-1.4194 ? 20.3427+-1.1601 ? string-validate-input 4.4093+-0.7144 4.1877+-0.0550 might be 1.0529x faster <arithmetic> * 4.9324+-0.1621 ? 4.9461+-0.1401 ? might be 1.0028x slower <geometric> 3.8557+-0.0692 3.8526+-0.0870 might be 1.0008x faster <harmonic> 3.1461+-0.0199 3.1327+-0.0499 might be 1.0043x faster
Comment on attachment 212943 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=212943&action=review > Source/JavaScriptCore/API/JSCallbackObjectFunctions.h:601 > Why keep this blank line? > Source/JavaScriptCore/API/JSCallbackObjectFunctions.h:604 > + VM& vm = exec->vm(); > + JSObject* o = JSCallbackFunction::create(vm, thisObj->globalObject(), callAsFunction, name); > + thisObj->putDirect(vm, propertyName, o, entry->attributes); Do local variables pay back in cases like this?
(In reply to comment #3) > (From update of attachment 212943 [details]) > View in context: https://bugs.webkit.org/attachment.cgi?id=212943&action=review > > > Source/JavaScriptCore/API/JSCallbackObjectFunctions.h:604 > > + VM& vm = exec->vm(); > > + JSObject* o = JSCallbackFunction::create(vm, thisObj->globalObject(), callAsFunction, name); > > + thisObj->putDirect(vm, propertyName, o, entry->attributes); > > Do local variables pay back in cases like this? I used to think that it doesn't. Then I looked at assembly output and saw a lot more loads than I expected. For example, JSGlobalObject::reset() shrunk ~4kB when I cached the VM in a local. Since then I've become very suspicious of the compiler's ability to see which values aren't changing. I checked now, and this function does not benefit from the local variable. However in this same patch, JSPromisePrototypeFuncCatch does benefit. It shrinks 14 bytes on x86_64 from caching the VM for a single re-use. (Return of an old cargo cult?)
Committed r156624: <http://trac.webkit.org/changeset/156624>