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> Also, in modern compilers, parameter variables are mostly passed to functions via registers, with the stack not being involved at all. Given that this is a C

by mhh__ 6y ago

> Also, in modern compilers, parameter variables are mostly passed to functions via registers, with the stack not being involved at all. Given that this is a C++ thread I'll be pedantic and say that this is really the ABI rather than the compiler as per se.

gumby 6y ago
ABI is a factor in every language;* so I’m not sure I understand the point you’re trying to make. * even interpreted ones, though the calling conventions and layout are quite different from what is typically written up in the documentation of most compiled languages.
- mhh__ 6y ago
  The term "modern compiler" was used, which implies that an old compiler might (say) not do so despite complying with some ABI, i.e. the registers aren't an optimization.
  - gumby 6y ago
    I have never used a compiler that didn't allocate frames in a single move of the sp, and I've been using compilers since the 1970. Surely "modern" has to mean some change more recent than that.
    - mhh__ 6y ago
      That isn't the part of your comment I was block-quoting.
zabzonk 6y ago
Given that the C++ Standard has nothing to say about an ABI (neither does the C Standard, for that matter), then what a compiler does on a particular platform, and what a platform ABI specifies (if it does) are possibly kind of linked.
- mhh__ 6y ago
  The word compiler is only mentioned 12 times in the whole standard give or take. My point was that it's not a question of whether the compiler is modern or not, i.e. I work with an old compiler backend on a modern system and it still gets the ABI correct even if it ends up spilling back to memory too often.