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> Go actually compiles the code to machine code directly True. > so it needs to have an assembler for its compiler. No, it doesn't need an assembler for this

> Go actually compiles the code to machine code directly True. > so it needs to have an assembler for its compiler. No, it doesn't need an assembler for this. As you said correctly, it compiles to machine code directly. While it was once fairly common to use assembly as an intermediate step, very few or any modern compilers do that. They just compile directly to binary machine code. Go does have a -S flag to generate assembly language so you can review the generated code more easily. But that assembly code isn't part of the compilation pipeline, it's just optional output for human review.

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- wrs 1y ago
  `-S` is a disassembler, or an assembly generator. You definitely want that when developing a compiler. But an assembler that goes the other direction, that’s entirely optional.
kbolino 1y ago
I think this is just half true. When dealing with purely high-level code (including C without inline assembly), the compiler doesn't need a discrete assembler. This much is true, and most modern compilers will not spit out assembly unless requested. However, there's usually still a stage of the compilation process where an assembly-like internal representation is used. Once the compiler has chosen which registers to use and where, and which instructions to use and in what order, etc., it's close to machine code but not fully there yet. At this point, jump targets will still be labels without concrete addresses, instructions will be still be referenced by mnemonic, etc. Serializing this internal representation as assembly will generally produce more readable code than disassembling the final binary. So it's not assembly exactly, but it's pretty close.
- Stratoscope 1y ago
  Yes, very true! And more accurate than what I wrote. The point I meant to make was that assembly language in the text form that we would use is not part of the compilation process. But I oversimplified my description rather badly. Interestingly, Go also has a -d=ssa/all switch that outputs not just an assembly representation of the final code, but also the results of each optimization pass. Here is a discussion I had with ChatGPT about this: https://chatgpt.com/share/6859aea5-df1c-8012-be70-f2361060fb5b https://chatgpt.com/share/6859aea5-df1c-8012-be70-f2361060fb...
MangoToupe 1y ago
The division between 'assembler' and 'generating machine code directly' can be pretty blurry depending on the interface. I imagine a compiler would basically interleave what the assembler would normally do with the code generation. I don't think this really yields deep insight, though, you're effectively doing the same thing either way.

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wrs 1y ago
`-S` is a disassembler, or an assembly generator. You definitely want that when developing a compiler. But an assembler that goes the other direction, that’s entirely optional.

kbolino 1y ago

I think this is just half true. When dealing with purely high-level code (including C without inline assembly), the compiler doesn't need a discrete assembler. This much is true, and most modern compilers will not spit out assembly unless requested. However, there's usually still a stage of the compilation process where an assembly-like internal representation is used. Once the compiler has chosen which registers to use and where, and which instructions to use and in what order, etc., it's close to machine code but not fully there yet. At this point, jump targets will still be labels without concrete addresses, instructions will be still be referenced by mnemonic, etc. Serializing this internal representation as assembly will generally produce more readable code than disassembling the final binary. So it's not assembly exactly, but it's pretty close.

Stratoscope 1y ago
Yes, very true! And more accurate than what I wrote. The point I meant to make was that assembly language in the text form that we would use is not part of the compilation process. But I oversimplified my description rather badly. Interestingly, Go also has a -d=ssa/all switch that outputs not just an assembly representation of the final code, but also the results of each optimization pass. Here is a discussion I had with ChatGPT about this: https://chatgpt.com/share/6859aea5-df1c-8012-be70-f2361060fb5b https://chatgpt.com/share/6859aea5-df1c-8012-be70-f2361060fb...

MangoToupe 1y ago

The division between 'assembler' and 'generating machine code directly' can be pretty blurry depending on the interface. I imagine a compiler would basically interleave what the assembler would normally do with the code generation. I don't think this really yields deep insight, though, you're effectively doing the same thing either way.