From 33e7f5c6728e4f2f21296d895fd8941aba5c8767 Mon Sep 17 00:00:00 2001
From: malik672 <aremumalik05@gmail.com>
Date: Fri, 21 Nov 2025 18:04:37 +0100
Subject: [PATCH] optimize target_for_value

---
 compiler/rustc_middle/src/mir/terminator.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/compiler/rustc_middle/src/mir/terminator.rs b/compiler/rustc_middle/src/mir/terminator.rs
index cd447d4ed992b..34dbcac4cbc30 100644
--- a/compiler/rustc_middle/src/mir/terminator.rs
+++ b/compiler/rustc_middle/src/mir/terminator.rs
@@ -84,7 +84,14 @@ impl SwitchTargets {
     /// branch if there's not a specific match for the value.
     #[inline]
     pub fn target_for_value(&self, value: u128) -> BasicBlock {
-        self.iter().find_map(|(v, t)| (v == value).then_some(t)).unwrap_or_else(|| self.otherwise())
+        let value = Pu128(value);
+        if let Some(idx) = self.values.iter().position(|&v| v == value) {
+            // SAFETY: Invariant ensures targets.len() == values.len() + 1.
+            // If index is in values, it is valid in targets.
+            unsafe { *self.targets.get_unchecked(idx) }
+        } else {
+            self.otherwise()
+        }
     }
 
     /// Adds a new target to the switch. Panics if you add an already present value.