>That idea of a universal/generic VM supporting many languages has been tried many times, with limited success, for example with the JVM, CLR, or Parrot. What makes this different?
What's different this time is that WASM flips the timeline backwards from how Sun JVM and Microsoft CLR tried to do it.
- JVM/CLR : create virtual machine & IL instruction codes specification & runtime first, then later try to distribute widely as possible and hope for universal client adoption. In other words, the "intermediate language vm" will be so compelling that it causes industry to spread it throughout the landscape. This hope was only partially true. JVM/CLR did spread on desktop & servers but fell short on web browsers with Java Applets and Microsoft Silverlight. JVM/CLR also never got widely adopted on mobile platforms.
- WASM has opposite timeline : take something (aka Javascript) that's already distributed and adopted industry-wide and work backwards from that to create a "virtual machine & IL instruction codes specification & runtime".
In that view, Javascript (the so-called "toy language") was the 20-year long "Trojan Horse" of getting wide distribution on all clients first. Now the industry says: "Hey, did anyone notice that we finally have a universal runtime (Javascript) on server+desktop+browser+mobile?!? Let's make it fast by creating an IL runtime!!!"
There were a few technical issues such as Sun JVM not having raw pointers which makes it not a good performing target for pointer-based languages like C/C++. And MS CLR wasn't available on macOS (except for Silverlight minimal-CLR). But those technical limitations don't have as much explanatory power as the Javascript-as-harmless-trojan-horse-distribution timeline.
Java applets came out at the same time as the original release of Java, and were definitely part of Sun's strategy for Java, but providing a platform for other languages wasn't in the plan. Others came because they specified the virtual machine so clearly that it was actually possible to target (unlike Python's), but if you look at the Java bytecode it's pretty clear that it exists to serve one language and all others must adapt. You calling the JVM not having raw pointers a "technical issue" makes it sound like it was a mistake on Java's part, but that's just a side effect of only intending to support a language that doesn't have raw pointers.
Meanwhile, WASM isn't just JavaScript-made-fast—JavaScript is already very fast through JIT compilation, and it's not obvious that compiling it ahead of time to WASM would make it faster. I'm not even aware of any efforts to do so. WASM is actually what you seem to think Java was—a new runtime built for the web and designed to allow many languages to target it flawlessly. To the extent WASM has an advantage over previous shared runtimes, it's that it was designed to be shared from the start and was spearheaded by the largest modern platforms—the browsers themselves are the true Trojan horse here.
> take something (aka Javascript) that's already distributed and adopted industry-wide and work backwards from that to create a "virtual machine & IL instruction codes specification & runtime".
I don't understand this. WASM is not JavaScript: it can't do things that JavaScript can do (such as directly access the DOM) and JS can't do things that WASM can do (such as pointer arithmetic). Their abstractions are totally different, which is why they complement each other. JS does not run in the WASM virtual machine. Other than the fact that they both run in a web browser, they have almost nothing in common.
So I think your analogy fails. WASM is not a JS IL, it's a separate IL that happens to be distributed by the same mechanism. As such, it can still fail and is still vulnerable to the hubris of the JVM, wherein a single memory model was selected for all platforms and all (higher-level) languages.
>I don't understand this. WASM is not JavaScript: [...] So I think your analogy fails. WASM is not a JS IL, it's a separate IL
Yes, that's what it looks like now. To explain the Javascript-to-WASM evolution, we use the concept of the "Overton Window" shifting the industry by almost imperceptible degrees :
https://en.wikipedia.org/wiki/Overton_window
- phase 1: 1995 Javascript the "toy language" but no IL. The industry doesn't need to be "afraid" of a toy scripting language because it's just there to make the monkey dance.[1]
- phase 2: 2000s Javascript is being extended XMLHttpRequest() to create "serious" apps like drag & drop email and Google Maps
- phase 3: 2013 extensive use of Javascript everywhere motivates a performance hack by creating subset in "asm.js" : https://en.wikipedia.org/wiki/Asm.js
- phase 4: 2017 instead of "asm.js" (and also using some Google NaCl ideas), the industry finally collaborates to create WASM to further optimize away the inefficient "asm.js"
Since WASM today looks a lot like what JVM/CLR hoped to accomplish, why couldn't we have skipped the whole circuitous route of Javascript-then-WASM instead of just having "WASM in 1995" in the first place?!? Because of the Overton Window. If WASM was there from the beginning, it would have been too "threatening" in 1990s and corporate firewall admins would want to block all http/html that had it. ("Let's prevent WASM viruses") Javascript on the other hand is just for animating monkeys so there's no need to block it. That's how you eventually get universal distribution across clients including smartphones. With Javascript code already entrenched everywhere, it's easier to slide the Overton Window over to WASM.
WASM didn't get created in a vacuum. It's existence is directly tied back to Javascript's usage and growth.
> Since WASM today looks a lot like what JVM/CLR hoped to accomplish
WASM is actually much lower-level than JVM or CLR, there's basically no comparison. The main feature in both CLR and JVM (accounting for the bulk of their complexity) is their object model which has no equivalent in WASM-GC, the closest thing (while quite different nonetheless) is probably the WASM components proposal which is still vaporware.
(Could WASM-GC have shipped in the mid-1990s? Quite unlikely, the FLOSS community was in its infancy back then and JVM applets were seen as state of the art. Even the Cyclone language was only created in the mid-2000s, and having full type- and memory-safety with C-like performance and no need for pervasive GC was unthinkable prior to that. The plan9 folks had Limbo and Dis which were somewhat simpler, but there was zero broader interest in using something like that over the JVM.)
Not to mention, JavaScript engines were essentially extended into supporting WebAssembly much like they were extended to optimize Asm.js. Browsers generally don't have entirely separate WebAssembly engines, parts of their existing JS engine are shared for WebAssembly. I think that makes the case pretty well!
That doesn't really make the case—JIT compiler backends are all pretty similar, so of course the browsers are going to reuse parts of their JavaScript JIT for WASM, but that doesn't make WASM "JavaScript, but fast". The only resemblance WASM has to JavaScript is it lives in the browser.
To be fair, as far as I can tell you are the first person to use the phrase "JavaScript, but fast" in this thread. Wasm's design isn't based on JS, obviously. It is, however, strongly inspired by ideas like asm.js and the existence of C -> JS compilers (among other things.) You can find more evidence of this than just HN commenters. Here's Google:
Heck, the same toolchain (Emscripten) that targeted asm.js became one of the defacto Wasm toolchains. They're not the same thing, but the path from which things evolved is not really open for much debate.
> Now the industry says: "Hey, did anyone notice that we finally have a universal runtime (Javascript) on server+desktop+browser+mobile?!? Let's make it fast by creating an IL runtime!!!"
If they'd said that we have a universal platform in the browser, make it fast, that would be different. It's the idea that the JavaScript runtime is going to be made faster by WASM that I'm objecting to.
>>"Hey, did anyone notice that we finally have a universal runtime (Javascript) on server+desktop+browser+mobile?!? Let's make _it_ fast by creating an IL runtime!!!"
Ok, I see the misunderstanding. The "_it_" I'm referring to is the "desire to run serious apps in that runtime". I wasn't claiming that WASM makes Javascript syntax faster.
jchw intepreted my meaning as I intended: From my PoV, they designed an IL runtime based on how some people were using JavaScript, aka inspired by Asm.js, not an IL runtime for or based on JavaScript.
My point is that history has now shown us that it's easier for Google to extend V8 engine to also run WASM, and for Mozilla to extend SpiderMonkey to also run WASM... rather than for Sun JVM applets to spread into all browsers as a universal runtime -- or for a JVM-bytecode-compatible engine to be embedded inside Chrome/Firefox.
Even though Javascript itself was not purposefully designed to be a universal compilation target for C/C++, it nevertheless opened a door to a universal bytecode runtime that the JVM/CLR did not.
Interesting. I think we are interpreting that statement quite differently.
From my PoV, they designed an IL runtime based on how some people were using JavaScript, aka inspired by Asm.js, not an IL runtime for or based on JavaScript.
I did not read that statement as saying Wasm was or was intending to be faster JS, at least not generally. Of course you are correct in that Wasm has absolutely nothing to do with JS on a lower level.
> 2013 extensive use of Javascript everywhere motivates a performance hack by creating subset in "asm.js" :
ASM.js was an attempt to make JavaScript a useable compilation target, not a performance hack for JavaScript programs. That effort did lead to people deciding that a new bytecode format was a better option, but the desire to compile to JavaScript was never about JavaScript itself, it was about trying to bring other languages to the frontend web. At the time the only way to do that was to compile to JavaScript.
I don't think you're wrong about the Overton window, but it's a lot more complicated than "JavaScript shifted the overton window". The actual history is one of people wanting to do more and more with web browsers in general until JavaScript became non-viable. WASM is far more a younger sibling of JavaScript than it is a descendant of it—both were born from the growth of the web.
What's different this time is that WASM flips the timeline backwards from how Sun JVM and Microsoft CLR tried to do it.
- JVM/CLR : create virtual machine & IL instruction codes specification & runtime first, then later try to distribute widely as possible and hope for universal client adoption. In other words, the "intermediate language vm" will be so compelling that it causes industry to spread it throughout the landscape. This hope was only partially true. JVM/CLR did spread on desktop & servers but fell short on web browsers with Java Applets and Microsoft Silverlight. JVM/CLR also never got widely adopted on mobile platforms.
- WASM has opposite timeline : take something (aka Javascript) that's already distributed and adopted industry-wide and work backwards from that to create a "virtual machine & IL instruction codes specification & runtime".
In that view, Javascript (the so-called "toy language") was the 20-year long "Trojan Horse" of getting wide distribution on all clients first. Now the industry says: "Hey, did anyone notice that we finally have a universal runtime (Javascript) on server+desktop+browser+mobile?!? Let's make it fast by creating an IL runtime!!!"
There were a few technical issues such as Sun JVM not having raw pointers which makes it not a good performing target for pointer-based languages like C/C++. And MS CLR wasn't available on macOS (except for Silverlight minimal-CLR). But those technical limitations don't have as much explanatory power as the Javascript-as-harmless-trojan-horse-distribution timeline.