On 11/22/2016 5:31 AM, Ilya Yaroshenko wrote:
Please add a module (core.intrinsics ?) which will contain all DMD intrinsics
similar to ldc.intrinsics. After each DMD release it is not clear what is
intrinsics and what is not. I need BSF intrinsics for Better C library Mir
Random [1], which should work without linking with DRuntime and Phobos. I can
use ldc.intrinsics for LDC, but have no idea about DMD. I want BSR and BSF
instructions to be generated instead of current _software_ implementation in
core.bitop.
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Philosophical Questions:
1. Why hight level stuff like BitRange is in core.bitop, but not in
std.bitmanip? If it should be in core, why it is public?
2. Why bsf and bsr do NOT use hardware instructions anymore?
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Please ping me for Phobos and DRuntime PRs if they are related to math and
numeric issues.
The definitive list of dmd intrinsics is here:
https://github.com/dlang/dmd/blob/master/src/toir.d#L349
It is definitive in the sense that it is what dmd actually does, rather than
what any documentation says it does :-)
There reason there isn't a specific core.intrinsics module is that essentially
any function in the library could be made an intrinsic by an implementation, and
it is up to the implementation to make such choices. Therefore, making a
function an intrinsic should not necessitate moving its location.
The bodies of 'intrinsic' functions exist to:
1. provide a reference implementation that documents what it does
2. provide a fallback if some implementation decides to not make it an
intrinsic. Such decisions are left up to the implementation.
3. the bodies are needed if the address of an intrinsic function is taken.
If an implementation does decide to make a certain function an intrinsic, the
function is not referenced from the object file and the library does not need to
be linked to.
bsr and bsf are dmd intrinsics. It's easy enough to verify by running obj2asm on
a dmd generated object file, and then grepping it for bsr/bsf instruction mnemonics.
