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MIR operators: clarify Shl/Shr handling of negative offsets

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This commit is contained in:
Ralf Jung 2024-05-15 08:22:53 +02:00
parent ac385a5af6
commit 0afd50e852
1 changed files with 6 additions and 2 deletions
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8
compiler/rustc_middle/src/mir/syntax.rs
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@ -1480,13 +1480,17 @@ pub enum BinOp {
BitOr,
/// The `<<` operator (shift left)
///
/// The offset is truncated to the size of the first operand and made unsigned before shifting.
/// The offset is (uniquely) determined as follows:
/// - it is "equal modulo LHS::BITS" to the RHS
/// - it is in the range `0..LHS::BITS`
Shl,
/// Like `Shl`, but is UB if the RHS >= LHS::BITS or RHS < 0
ShlUnchecked,
/// The `>>` operator (shift right)
///
/// The offset is truncated to the size of the first operand and made unsigned before shifting.
/// The offset is (uniquely) determined as follows:
/// - it is "equal modulo LHS::BITS" to the RHS
/// - it is in the range `0..LHS::BITS`
///
/// This is an arithmetic shift if the LHS is signed
/// and a logical shift if the LHS is unsigned.