From d7923d4b3828b1ce4330266172dc6a9515b163a3 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 10 Mar 2026 22:55:52 +0100
Subject: [PATCH] simd_add/sub/mul/neg: document overflow behavior

---
 library/core/src/intrinsics/simd.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/library/core/src/intrinsics/simd.rs b/library/core/src/intrinsics/simd.rs
index 5fb2102c319e..50d887197379 100644
--- a/library/core/src/intrinsics/simd.rs
+++ b/library/core/src/intrinsics/simd.rs
@@ -62,6 +62,7 @@
 /// Adds two simd vectors elementwise.
 ///
 /// `T` must be a vector of integers or floats.
+/// For integers, wrapping arithmetic is used.
 #[rustc_intrinsic]
 #[rustc_nounwind]
 pub const unsafe fn simd_add<T>(x: T, y: T) -> T;
@@ -69,6 +70,7 @@
 /// Subtracts `rhs` from `lhs` elementwise.
 ///
 /// `T` must be a vector of integers or floats.
+/// For integers, wrapping arithmetic is used.
 #[rustc_intrinsic]
 #[rustc_nounwind]
 pub const unsafe fn simd_sub<T>(lhs: T, rhs: T) -> T;
@@ -76,6 +78,7 @@
 /// Multiplies two simd vectors elementwise.
 ///
 /// `T` must be a vector of integers or floats.
+/// For integers, wrapping arithmetic is used.
 #[rustc_intrinsic]
 #[rustc_nounwind]
 pub const unsafe fn simd_mul<T>(x: T, y: T) -> T;
@@ -233,8 +236,7 @@
 /// Negates a vector elementwise.
 ///
 /// `T` must be a vector of integers or floats.
-///
-/// Rust panics for `-<int>::Min` due to overflow, but it is not UB with this intrinsic.
+/// For integers, wrapping arithmetic is used.
 #[rustc_intrinsic]
 #[rustc_nounwind]
 pub const unsafe fn simd_neg<T>(x: T) -> T;