WIP Introduce ConstValue::ScalarPair #115915
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WIP Replace ConstValue::Slice by ConstValue::ScalarPair Both the interpreter and codegen have dedicated paths for scalar pairs. Having one in ConstValue makes is able to represent all "immediate" values. In order to mitigate the increase in the size of the ConstValue struct, a first commit interns it.
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WIP Replace ConstValue::Slice by ConstValue::ScalarPair Both the interpreter and codegen have dedicated paths for scalar pairs. Having one in ConstValue makes is able to represent all "immediate" values. In order to mitigate the increase in the size of the ConstValue struct, a first commit interns it.
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WIP Replace ConstValue::Slice by ConstValue::ScalarPair Both the interpreter and codegen have dedicated paths for scalar pairs. Having one in ConstValue makes is able to represent all "immediate" values. In order to mitigate the increase in the size of the ConstValue struct, a first commit interns it.
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Finished benchmarking commit (f827ada): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
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Bootstrap: 636.351s -> 636.345s (-0.00%) |
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WIP Introduce ConstValue::ScalarPair Both the interpreter and codegen have dedicated paths for scalar pairs. Having one in ConstValue makes is able to represent all "immediate" values. In order to mitigate the increase in the size of the ConstValue struct, a first commit interns it.
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Finished benchmarking commit (1b3ed3e): comparison URL. Overall result: ❌✅ regressions and improvements - ACTION NEEDEDBenchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf. Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @bors rollup=never Instruction countThis is a highly reliable metric that was used to determine the overall result at the top of this comment.
Max RSS (memory usage)ResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
CyclesResultsThis is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.
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Bootstrap: 634.064s -> 635.805s (0.27%) |
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We had I have laid down my vision for how |
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| /// Represents a constant value in Rust. `Scalar` and `Slice` are optimizations for | ||
| /// array length computations, enum discriminants and the pattern matching logic. | ||
| #[derive(Copy, Clone, Debug, Eq, PartialEq, TyEncodable, TyDecodable, Hash)] | ||
| #[derive(HashStable, Lift)] | ||
| pub enum ConstValue<'tcx> { | ||
| pub enum ConstValueKind<'tcx> { | ||
| /// Used for types with `layout::abi::Scalar` ABI. | ||
| /// | ||
| /// Not using the enum `Value` to encode that this must not be `Uninit`. |
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I do wonder which enum this refers to... I think it's just a very outdated comment.^^
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| @@ -50,7 +57,7 @@ pub enum ConstValue<'tcx> { | |||
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| /// A value not representable by the other variants; needs to be stored in-memory. | |||
| /// | |||
| /// Must *not* be used for scalars or ZST, but having `&str` or other slices in this variant is fine. | |||
| /// Must *not* be used for scalars, scalar pairs or ZST. | |||
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Your const_to_op violates this rule for scalar pairs. Either the comment or const_to_op need to be updated.
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| @@ -65,35 +72,48 @@ pub enum ConstValue<'tcx> { | |||
| } | |||
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| #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))] | |||
| static_assert_size!(ConstValue<'_>, 32); | |||
| static_assert_size!(ConstValue<'_>, 8); | |||
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That doesn't seem like a useful assertion, it's an interned pointer now...
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| /// Used for types with `layout::abi::ScalarPair` ABI. | ||
| /// | ||
| /// Not using the enum `Value` to encode that this must not be `Uninit`. | ||
| ScalarPair(Scalar, Scalar), |
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We definitely don't want to have ScalarPair and Slice. Why would that make sense?
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Closing this as it is WIP and heavily bitrotted |
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Both the interpreter and codegen have dedicated paths for scalar pairs. Having one in ConstValue makes is able to represent all "immediate" values.
In order to mitigate the increase in the size of the ConstValue struct, a first commit interns it.