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target_features for bit manipulation instruction sets #30462

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gnzlbg opened this issue Dec 18, 2015 · 4 comments
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target_features for bit manipulation instruction sets #30462

gnzlbg opened this issue Dec 18, 2015 · 4 comments
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C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@gnzlbg
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gnzlbg commented Dec 18, 2015

There are currently no target features for bit manipulation instruction sets, in particular:

  • AMD's Advanced Bit Manipulation (ABM) and Trailing Bit Manipulation (TBM) instructions, and
  • Intel's Bit Manipulation Instructions (BMI1 and BMI2).

Since clang has macros to detect these I guess llvm offers the ability to obtain this functionality from the CPUID as well.

Wikipedia offers a pretty good and brief review of the situation. Basically all modern processors support ABM and BMI1. Modern Intel CPUs support BMI2, and next generation AMD CPUs will as well.

AMD also has TBM but these won't be supported anymore in future CPUs.

Huon's llvmin offers intrinsics for all these instruction sets but without a target config macro there is no way of wrapping these into a higher level safer abstraction portably.

So basically I would like to have target features to use in #[cfg(_)] for: amb, bmi1,bmi2, and tmb.
@gnzlbg
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gnzlbg commented Dec 18, 2015

Related to #29717.

@gnzlbg gnzlbg mentioned this issue Dec 18, 2015
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@gnzlbg gnzlbg mentioned this issue Jun 19, 2016
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gnzlbg added a commit to gnzlbg/rust that referenced this issue Jun 21, 2016
@gnzlbg
Support detecting all llc's x86 target features
081e5b4 
This commit adds support for detecting all of llc's target features for the x86/x86_64 architectures.

Closes rust-lang#30462.
Helps with rust-lang#29717 and rust-lang#34382.
This was referenced Jun 21, 2016
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@steveklabnik steveklabnik added C-enhancement Category: An issue proposing an enhancement or a PR with one. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels May 18, 2017
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Triage: no idea what the status is here, honestly.

@steveklabnik
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Triage: no idea what the status is here, honestly. @gnzlbg any update?

@gnzlbg
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gnzlbg commented Sep 24, 2018

This was fixed ages ago, and is already available on stable, e.g., #[cfg(target_feature = "bmi2")] :)

Thanks for the triage!

@gnzlbg gnzlbg closed this as completed Sep 24, 2018
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