Solipsism Gradient

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Re: iPad time

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richardl wrote:

Rainer, it is interesting to note that Adobe built their ActionScript/Flash compiler for iPhone on top of LLVM.

Thanks, I wasn’t aware of that. However, I don’t think that this invalidates my original argument, which is more based on Clang than on LLVM. Christopher Lloyd also remarked on this:

…Yet Adobe uses llvm for the compiled Flash, so they don’t like Adobe’s parser? silly.

Also thanks to Daveed Vandevoorde, who remarked that the LLVM bytecode isn’t as platform-independent as I thought – things like sizes of variables and ABIs (Application Binary Interfaces) stand in the way. Still, it’s not impossible to see Apple defining a generic target platform, in terms of sizes of pointers, integers and so forth, and a specific endianness and runtime ABI, and then staying within the bytecode for that.

Re: iPad time

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Posted by richardl:

Rainer Brockerhoff wrote:

Via John Gruber, I just saw an interesting post by Steve Cheney:

It?s pretty evident that Apple isn?t wed to individual suppliers. Not only are they back to creating their own chips, but they are also one of the only ‘compute’ companies to have used each of the top 3 processor architectures over time – ARM, x86, and Power PC.

…This week Apple confined developers to a specific set of tools (XCode [sic]).

…By telling developers to move to XCode tools, Apple is setting the stage to potentially switch architectures.

…In 2003, Apple advised developers to switch to XCode tools. …2 years later Apple moved to Intel across its entire Mac line.

…perhaps the A4 is NOT an ARM architecture. In fact, it?s highly possible that the A4 is a dual core Power Architecture…

The last sentence is of course false, as Gruber says; the A4 does run ARM code.

While I don’t think that forcing developers to switch to Xcode (which is the correct spelling_ means that Apple will soon be switching architectures on their iPad/iPhone line, or on their desktop/laptop line for that matter, Xcode does offer developers a future-proof environment that hasn’t been commented on by other observers: the Clang/LLV project. Briefly, Clang is a compiler frontend for C-based languages, backed by LLVM – which stands for “Low Level Virtual Machine”. Both projects are heavily backed and staffed by Apple.

Clang has been increasingly supported by Xcode as a substitute for the gcc compiler toolchain. The details are quite esoteric, but one interesting capability is that C-based languages – C, Objective-C and C++ – are compiled to the LLVM bytecode, which is then translated into native machine language by a back-end. The last phase could even happen in a just-in-time fashion, allowing apps to be distributed in LLVM code (therefore running on all current and future Apple machines). Some groups are even working on chips that execute LLVM bytecode directly.

In other words, it’s no coincidence that Apple is now instructing developers to switch to Clang-supported languages and their Clang-wrapping IDE (Xcode). There may not be an architecture switch coming soon, but Apple will have much more freedom in doing their own CPUs for iPad/iPhone, and more ammunition in negotations with Intel and other top-end chip companies.

Rainer, it is interesting to note that Adobe built their ActionScript/Flash compiler for iPhone on top of LLVM.

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