Another problem with the article is the description of how compilers work. In my experience over the years, the compilers that use assembly language as an inte

Another problem with the article is the description of how compilers work. In my experience over the years, the compilers that use assembly language as an intermediate form, and that require an assembler, are in the minority; and the majority of compilers that I have encountered go straight from (lowered) IR to machine code generation. As bla2 points out, it seems that the author has got entirely the wrong end of the stick. App thinning isn't related to bitcode. It's about delivering a program image that only contains the program for the instruction architecture of the downloading client. LLVM bitcode use is, rather, about holding off generating that final machine image until the point of download, rather than when the developer compiled the program, theoretically allowing improvements in code generation and IR lowering to be taken advantage of after a developer provides a compiled application to Apple. A better treatment of the subject appears to be https://imore.com/app-thinning-ios-9-explained https://imore.com/app-thinning-ios-9-explained .