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Which I think reinforces what I said about about languages that give sufficient hints to the compiler to let it get the optimisation right, and opens the question about how a language can best solicit advice without insisting that the programmer use predefined functions (written in a particular style and heavy with hints) or litter his code with pragmata.

Mark Morgan Lloyd
– Mark Morgan Lloyd

2020-09-14 06:32:25 +00:00
Commented Sep 14, 2020 at 6:32
2

A key insight here might be that a good C programmer can write code which is optimizer-friendly. There's very little in real-world problems that can be expressed only in assembly. One hint in this regard is restrict in C99 - it's been added to make code optimizer-friendly, but in the intervening 20 years no similar extensions have been added.

MSalters
– MSalters

2020-09-14 09:14:43 +00:00
Commented Sep 14, 2020 at 9:14
@MSalters: Unfortunately, some compilers make it annoyingly difficult to write code that is optimizer friendly. For example, clang and gcc process restrict in such a way that within a statement like if (p==q) doSomething(p); the value passed to doSomething won't necessarily be recognized as being based upon p. Although the Standard's definition of "based upon" is sufficiently ambiguous that such behavior might be conforming, nothing in the Standard would indicate any intention to forbid comparisons between restrict-qualified pointers and anything else.

supercat
– supercat

2020-09-14 19:03:51 +00:00
Commented Sep 14, 2020 at 19:03

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