On Wednesday, 23 October 2019 at 12:01:47 UTC, Per Nordlöw wrote:
On Wednesday, 23 October 2019 at 11:33:56 UTC, kinke wrote:
For your example, the template is inferred to be @safe, and
`-release` only elides bounds checks in @system functions
(corresponding to `-boundscheck=safeonly`). Use
`-boundscheck=off` to elide it in all functions.
Thanks. But I'm talking about the compiler being able to figure
out that the expression
haystack[0 .. needle.length]
_never_ (regardless of compiler flags) needs any range checking
because it is _only_ run when
haystack.length >= needle.length
. Do you follow?
Actually what you want is that the compiler uses a loop-invariant
to only to bounds-checking once on the first loop entry?
That's quite tricky to do for all cases.
What you can do manually is to index the .ptr property which will
decay the array to a pointer, and on a pointer you cannot and
therefore will not do boundschecking
just replace x = a[i] with x = a.ptr[i];
