Some builtin intrinsics that are not constexpr but could be

[RKSimon]

Bugzilla Link	47249
Version	unspecified
OS	Windows NT
CC	@erichkeane,@zygoloid
Fixed by commit(s)	e7d9182 , 2ceac91 , 00158ae

This isn't exhaustive, but all are low hanging fruit:

bit twiddling:

• __builtin_bitreverse D86339 e7d9182
• __builtin_rotateleft D86342 2ceac91
• __builtin_rotateright D86342 2ceac91

vectors:

• __builtin_convertvector
• __builtin_shufflevector

-fms-extensions variants:

• __lzcnt16, __lzcnt, __lzcnt64 D157420 00158ae
• __popcnt16, __popcnt, __popcnt64 D157420 00158ae
• _rotl8, _rotl16, _rotl, _rotl64, _lrotl
• _rotr8, _rotr16, _rotr, _rotr64, _lrotr

[RKSimon]

https://reviews.llvm.org/D86339 - __builtin_bitreverse support

[RKSimon]

https://reviews.llvm.org/D86342 - __builtin_rotateleft / __builtin_rotateright support

[RKSimon]

https://reviews.llvm.org/D86339 - __builtin_bitreverse support

e7d9182

[RKSimon]

https://reviews.llvm.org/D86342 - __builtin_rotateleft /
__builtin_rotateright support

2ceac91

[chfast]

Also __builtin_addc and __builtin_subc?

[Endilll]

Feels like a good first issue.

CC @shafik @AaronBallman

[RKSimon]

Feels like a good first issue.

Agreed although they need splitting into separate tasks - the ms-extension variants are pretty trivial, but convertvector might be harder and I expect shufflevector to be tricky.

[shafik]

@RKSimon Looking at the PRs above they look relatively straight forward.

[llvmbot]

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[alexguirre]

Hi, seems like the ROTL/ROTR ms-extension intrinsics were already made constexpr in a1dc3d2.

I would like to work on the remaining intrinsics.

[RKSimon]

Hi, seems like the ROTL/ROTR ms-extension intrinsics were already made constexpr in a1dc3d2.

I would like to work on the remaining intrinsics.

Great - I'd recommend starting with the the lzcnt/popcnt ms-extension intrinsics as they should be similar to the previous cases.

After that, __builtin_convertvector is probably easier than __builtin_shufflevector but both are very different to the other intrinsics, and will require some refactoring for missing vector type special case handling.

[alexguirre]

Submitted a patch for lzcnt/popcnt https://reviews.llvm.org/D157420

[BertalanD]

Also __builtin_addc and __builtin_subc?

I'm on it: D156156. I'll try to find time to finish it this week.