computeUpdatedPrediction() will return PredictOther when a value profile has a mix of types. PredictOther means Undefined or Null, so that's clearly wrong. Currently this should be benign, in the sense that it should just cause speculation failures. But that's not so great for performance.
Created attachment 110724 [details] the patch Benchmark report for SunSpider, V8, and Kraken. VMs tested: "TipOfTree" at /Volumes/Data/pizlo/OpenSource/WebKitBuild/Release/jsc "FixProfile" at /Volumes/Data/pizlo/senary/OpenSource/WebKitBuild/Release/jsc Collected 12 samples per benchmark/VM, with 4 VM invocations per benchmark. 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 FixProfile SunSpider: 3d-cube 7.3870+-0.1434 7.2386+-0.1102 might be 1.0205x faster 3d-morph 8.3775+-0.8625 7.7184+-0.1144 might be 1.0854x faster 3d-raytrace 7.6431+-0.2087 ? 7.7190+-0.2071 ? access-binary-trees 1.6935+-0.0550 1.6806+-0.0443 access-fannkuch 6.3731+-0.0945 6.3581+-0.0887 access-nbody 3.3125+-0.0656 3.3009+-0.0592 access-nsieve 2.5846+-0.0640 ? 2.6321+-0.0843 ? might be 1.0184x slower bitops-3bit-bits-in-byte 1.7253+-0.0274 ? 1.7582+-0.0381 ? might be 1.0191x slower bitops-bits-in-byte 2.8091+-0.0514 2.7252+-0.0738 might be 1.0308x faster bitops-bitwise-and 3.3941+-0.0747 3.3556+-0.1009 might be 1.0115x faster bitops-nsieve-bits 5.5153+-0.0988 5.5105+-0.1199 controlflow-recursive 2.1138+-0.0531 ? 2.1456+-0.0747 ? might be 1.0151x slower crypto-aes 6.8299+-0.1630 6.7437+-0.1648 might be 1.0128x faster crypto-md5 2.8610+-0.0692 2.8318+-0.0672 might be 1.0103x faster crypto-sha1 2.5423+-0.0838 2.4897+-0.0638 might be 1.0211x faster date-format-tofte 9.9869+-0.1586 ? 10.1792+-0.1745 ? might be 1.0192x slower date-format-xparb 9.0433+-0.2143 ? 9.2611+-0.2927 ? might be 1.0241x slower math-cordic 6.3837+-0.0624 ? 6.4447+-0.0731 ? math-partial-sums 7.5753+-0.1140 ? 7.6394+-0.1411 ? math-spectral-norm 2.8914+-0.0627 2.8819+-0.0647 regexp-dna 10.7096+-0.1479 ? 10.7654+-0.1319 ? string-base64 5.2383+-0.0718 ? 5.3516+-0.0729 ? might be 1.0216x slower string-fasta 6.5073+-0.1150 ? 6.5156+-0.1362 ? string-tagcloud 11.2380+-0.2166 11.1545+-0.2043 string-unpack-code 20.6586+-0.2970 ? 20.9446+-0.7071 ? might be 1.0138x slower string-validate-input 6.3705+-0.1253 ? 6.3803+-0.1194 ? <arithmetic> * 6.2217+-0.0484 6.2202+-0.0301 <geometric> 5.1214+-0.0359 5.1132+-0.0210 <harmonic> 4.2060+-0.0348 4.1995+-0.0276 TipOfTree FixProfile V8: crypto 72.8527+-0.4478 72.4592+-0.2900 deltablue 225.1709+-2.3335 223.6545+-1.7005 earley-boyer 91.8261+-0.3565 ? 92.0220+-0.4391 ? raytrace 59.7300+-0.7757 ^ 57.8942+-0.3434 ^ definitely 1.0317x faster regexp 106.3592+-0.3718 105.3202+-0.9491 richards 186.9082+-6.5842 182.6153+-0.3850 might be 1.0235x faster splay 95.6470+-0.8616 95.0531+-0.3847 <arithmetic> 119.7849+-0.6726 ^ 118.4312+-0.3341 ^ definitely 1.0114x faster <geometric> * 107.9463+-0.4507 ^ 106.7343+-0.3124 ^ definitely 1.0114x faster <harmonic> 98.5508+-0.4177 ^ 97.3485+-0.3249 ^ definitely 1.0123x faster TipOfTree FixProfile Kraken: ai-astar 501.1981+-3.1509 500.6884+-6.7670 audio-beat-detection 192.4552+-0.6351 ? 192.6383+-0.8518 ? audio-dft 271.7373+-6.4749 268.6449+-1.9443 might be 1.0115x faster audio-fft 125.2747+-0.7431 124.7780+-0.7993 audio-oscillator 252.5998+-2.1763 ? 254.1639+-2.6871 ? imaging-darkroom 420.0759+-1.9578 417.9027+-1.5970 imaging-desaturate 218.0847+-0.4997 ! 219.9462+-0.8396 ! definitely 1.0085x slower imaging-gaussian-blur 557.8666+-1.8411 556.8822+-2.5415 json-parse-financial 54.7763+-0.2994 ? 55.0612+-0.2650 ? json-stringify-tinderbox 68.9615+-1.0041 68.5430+-0.4149 stanford-crypto-aes 130.8375+-1.5580 ? 132.8984+-1.7029 ? might be 1.0158x slower stanford-crypto-ccm 104.6360+-0.6860 ? 104.6884+-1.2097 ? stanford-crypto-pbkdf2 194.7741+-0.7511 ^ 192.6652+-0.5280 ^ definitely 1.0109x faster stanford-crypto-sha256-iterative 71.8618+-1.0272 71.0898+-0.4693 might be 1.0109x faster <arithmetic> * 226.0814+-0.7470 225.7565+-0.7902 <geometric> 177.4289+-0.7113 177.2551+-0.5811 <harmonic> 139.1710+-0.7181 139.0418+-0.5170 TipOfTree FixProfile All benchmarks: <arithmetic> 88.6255+-0.3154 88.3263+-0.2447 <geometric> 23.1825+-0.1145 23.1166+-0.0570 <harmonic> 7.3978+-0.0599 7.3855+-0.0473 TipOfTree FixProfile Geomean of preferred means: <scaled-result> 53.3485+-0.2212 53.1184+-0.1106
Landed in r97294.