codegen: tweak/extend shift comments

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/rustc_codegen_ssa/src/traits/builder.rs b/compiler/rustc_codegen_ssa/src/traits/builder.rs
index fdeccb90700..11a8d218ae3 100644
--- a/compiler/rustc_codegen_ssa/src/traits/builder.rs
+++ b/compiler/rustc_codegen_ssa/src/traits/builder.rs
@@ -110,8 +110,16 @@ pub trait BuilderMethods<'a, 'tcx>:
     fn frem(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
     fn frem_fast(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
     fn frem_algebraic(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
+    /// Generate a left-shift. Both operands must have the same size. The right operand must be
+    /// interpreted as unsigned and can be assumed to be less than the size of the left operand.
     fn shl(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
+    /// Generate a logical right-shift. Both operands must have the same size. The right operand
+    /// must be interpreted as unsigned and can be assumed to be less than the size of the left
+    /// operand.
     fn lshr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
+    /// Generate an arithmetic right-shift. Both operands must have the same size. The right operand
+    /// must be interpreted as unsigned and can be assumed to be less than the size of the left
+    /// operand.
     fn ashr(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
     fn unchecked_sadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;
     fn unchecked_uadd(&mut self, lhs: Self::Value, rhs: Self::Value) -> Self::Value;