Per VognsenFeb 23
Saw this when randomly flipping through the code base of something posted to Lobsters. C or C++ is not the language for you if you think you can write code like that. https://c.godbolt.org/z/8q5zoh6Ke
Compiler Explorer - C (x86-64 gcc 15.2)

// https://github.com/abdimoallim/jit typedef int32_t i32; typedef uint8_t u8; typedef size_t usz; typedef struct { u8* buf; usz len; } jit_buf; void jit_ensure(jit_buf* j, usz n) {} // bad void jit_emit_i32(jit_buf* j, i32 v) { jit_ensure(j, 4); j->buf[j->len + 0] = (u8)(v); j->buf[j->len + 1] = (u8)(v >> 8); j->buf[j->len + 2] = (u8)(v >> 16); j->buf[j->len + 3] = (u8)(v >> 24); j->len += 4; } // good void jit_emit_i32_fixed(jit_buf* j, i32 v) { jit_ensure(j, 4); u8* buf = j->buf; usz len = j->len; buf[len + 0] = (u8)(v); buf[len + 1] = (u8)(v >> 8); buf[len + 2] = (u8)(v >> 16); buf[len + 3] = (u8)(v >> 24); j->len = len + 4; } int main() {}

Show threadPer VognsenFeb 23
There's a certain systems language with pervasive noalias guarantees where you can write code like that but C is assuredly not that language.
Show threadArseny KapoulkineFeb 23
@pervognsen eh in that language every [] is a branch so it’s not magically better
Show threadJonathan Müller
@zeux @pervognsen You can use get_unchecked.
Feb 23 at 7:01amWeb
Show threadArseny KapoulkineFeb 23
@foonathan @pervognsen In both cases, the generated code for naive version is suboptimal and changing the code to get optimal codegen isn’t too hard.