Fix #69841 by updating LLVM submodule. Includes regression test for i…

…ssue 69841.

src/test/ui/issues/issue-69841.rs

@@ -0,0 +1,30 @@
+// This is a regression test for issue rust-lang/rust#69841, which exposed an
+// LLVM bug which needed a fix to be backported.
+
+// run-pass
+
+fn main() {
+    let buffer = [49u8, 10];
+    let mut a : u64 = 0;
+    'read: loop {
+        for c in &buffer {
+            match c {
+                48..=57 => {
+                    a*= 10;
+                    a+= *c as u64 - 48;
+                }
+                10 => {
+                    break 'read;
+                }
+                _ => {
+                    unsafe { std::hint::unreachable_unchecked() };
+                }
+            }
+        }
+    }
+    if a == 1 {
+        println!("What did you expect?");
+    } else {
+        panic!("this should be unreachable.");
+    }
+}