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Auto merge of #119911 - NCGThompson:is-statically-known, r=oli-obk

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Replacement of #114390: Add new intrinsic `is_var_statically_known` and optimize pow for powers of two

This adds a new intrinsic `is_val_statically_known` that lowers to [``@llvm.is.constant.*`](https://llvm.org/docs/LangRef.html#llvm-is-constant-intrinsic).` It also applies the intrinsic in the int_pow methods to recognize and optimize the idiom `2isize.pow(x)`. See #114390 for more discussion.

While I have extended the scope of the power of two optimization from #114390, I haven't added any new uses for the intrinsic. That can be done in later pull requests.

Note: When testing or using the library, be sure to use `--stage 1` or higher. Otherwise, the intrinsic will be a noop and the doctests will be skipped. If you are trying out edits, you may be interested in [`--keep-stage 0`](https://rustc-dev-guide.rust-lang.org/building/suggested.html#faster-builds-with---keep-stage).

Fixes #47234
Resolves #114390
`@Centri3`
This commit is contained in:
bors 2024-01-25 05:16:53 +00:00
commit 50a067d7f8
1 changed files with 6 additions and 0 deletions
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6
src/intrinsics/mod.rs
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@ -443,6 +443,12 @@ fn codegen_regular_intrinsic_call<'tcx>(
ret.write_cvalue(fx, a);
}
sym::is_val_statically_known => {
intrinsic_args!(fx, args => (_a); intrinsic);
let res = fx.bcx.ins().iconst(types::I8, 0);
ret.write_cvalue(fx, CValue::by_val(res, ret.layout()));
}
sym::breakpoint => {
intrinsic_args!(fx, args => (); intrinsic);