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Lower unchecked_div/_rem to MIR's BinOp::Div/Rem - #112168
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rustbot
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Jun 1, 2023
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r? @oli-obk (rustbot has picked a reviewer for you, use r? to override) |
rustbot
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Some changes occurred to MIR optimizations cc @rust-lang/wg-mir-opt Some changes occurred in compiler/rustc_codegen_cranelift cc @bjorn3 Some changes occurred to the CTFE / Miri engine cc @rust-lang/miri |
RalfJung
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Jun 1, 2023
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The MIR comment only mentions 0, not overflow. However the Miri implementation makes div and rem also UB on overflow. We should probably update the MIR comment then. |
rustbot
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Jun 2, 2023
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This PR changes MIR cc @oli-obk, @RalfJung, @JakobDegen, @davidtwco, @celinval, @vakaras |
scottmcm
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Jun 2, 2023
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Updated the comments on |
oli-obk
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Jun 2, 2023
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@bors r+ |
bors
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Jun 2, 2023
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Jun 2, 2023
…mpiler-errors Rollup of 6 pull requests Successful merges: - rust-lang#109609 (Separate AnonConst from ConstBlock in HIR.) - rust-lang#112166 (bootstrap: Rename profile = user to profile = dist) - rust-lang#112168 (Lower `unchecked_div`/`_rem` to MIR's `BinOp::Div`/`Rem`) - rust-lang#112183 (Normalize anon consts in new solver) - rust-lang#112211 (pass `--lib` to `x doc`) - rust-lang#112223 (Don't ICE in new solver when auto traits have associated types) r? `@ghost` `@rustbot` modify labels: rollup
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Jun 15, 2023
…o-mir, r=oli-obk Lower `unchecked_div`/`_rem` to MIR's `BinOp::Div`/`Rem` As described in <https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.BinOp.html#variant.Div>, the ordinary `BinOp`s for these are already UB for division by zero ([or overflow](https://llvm.org/docs/LangRef.html#sdiv-instruction), [demo](https://rust.godbolt.org/z/71e7P7Exh)), as MIR building is responsible for inserting code to panic for those cases regardless of whether the overflow checks are enabled. So we can lower these in the same arm that lowers `wrapping_add` to MIR `BinOp::Add` and such, as all these cases turn into ordinary `Rvalue::BinaryOp`s.
This was referenced Jun 21, 2023
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As described in https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/mir/enum.BinOp.html#variant.Div, the ordinary
BinOps for these are already UB for division by zero (or overflow, demo), as MIR building is responsible for inserting code to panic for those cases regardless of whether the overflow checks are enabled.So we can lower these in the same arm that lowers
wrapping_addto MIRBinOp::Addand such, as all these cases turn into ordinaryRvalue::BinaryOps.