Make named asm_labels lint not trigger on hexagon register spans

Fixes #143021

Author: androm3da

compiler/rustc_lint/src/builtin.rs

@@ -2867,6 +2867,44 @@ enum AsmLabelKind {
     Binary,
 }
 
+/// Checks if a potential label is actually a Hexagon register span notation.
+///
+/// Hexagon assembly uses register span notation like `r1:0`, `V5:4.w`, `p1:0` etc.
+/// These follow the pattern: `[letter][digit(s)]:[digit(s)][optional_suffix]`
+///
+/// Returns `true` if the string matches a valid Hexagon register span pattern.
+fn is_hexagon_register_span(possible_label: &str) -> bool {
+    if possible_label.len() < 3 {
+        return false;
+    }
+
+    let mut chars = possible_label.chars();
+    let start = chars.next().unwrap();
+
+    // Must start with a letter (r, V, p, etc.)
+    if !start.is_ascii_alphabetic() {
+        return false;
+    }
+
+    let rest = &possible_label[1..];
+    let Some(colon_idx) = rest.find(':') else {
+        return false;
+    };
+
+    let (before_colon, after_colon_with_colon) = rest.split_at(colon_idx);
+    let after_colon = &after_colon_with_colon[1..]; // Skip the ':'
+
+    // Check if before colon is all digits and non-empty
+    if before_colon.is_empty() || !before_colon.chars().all(|c| c.is_ascii_digit()) {
+        return false;
+    }
+
+    // Check if after colon starts with digits (may have suffix like .w, .h)
+    let digits_after = after_colon.chars().take_while(|c| c.is_ascii_digit()).collect::<String>();
+
+    !digits_after.is_empty()
+}
+
 impl<'tcx> LateLintPass<'tcx> for AsmLabels {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'tcx>) {
         if let hir::Expr {
@@ -2940,6 +2978,14 @@ impl<'tcx> LateLintPass<'tcx> for AsmLabels {
                             break 'label_loop;
                         }
 
+                        // Check for Hexagon register span notation (e.g., "r1:0", "V5:4", "V3:2.w")
+                        // This is valid Hexagon assembly syntax, not a label
+                        if matches!(cx.tcx.sess.asm_arch, Some(InlineAsmArch::Hexagon))
+                            && is_hexagon_register_span(possible_label)
+                        {
+                            break 'label_loop;
+                        }
+
                         for c in chars {
                             // Inside a template format arg, any character is permitted for the
                             // puproses of label detection because we assume that it can be

tests/ui/asm/hexagon-register-pairs.rs

@@ -0,0 +1,36 @@
+//@ add-core-stubs
+//@ compile-flags: --target hexagon-unknown-linux-musl
+//@ needs-llvm-components: hexagon
+
+#![feature(no_core, asm_experimental_arch)]
+#![crate_type = "lib"]
+#![no_core]
+
+extern crate minicore;
+use minicore::*;
+
+fn test_register_spans() {
+    unsafe {
+        // These are valid Hexagon register span notations, not labels
+        // Should NOT trigger the named labels lint
+
+        // General register pairs
+        asm!("r1:0 = memd(r29+#0)", lateout("r0") _, lateout("r1") _);
+        asm!("r3:2 = combine(#1, #0)", lateout("r2") _, lateout("r3") _);
+        asm!("r15:14 = memd(r30+#8)", lateout("r14") _, lateout("r15") _);
+        asm!("memd(r29+#0) = r5:4", in("r4") 0u32, in("r5") 0u32);
+
+        // Vector register pairs (hypothetical since we can't actually use them without HVX)
+        asm!("nop // V5:4 = vadd(V3:2, V1:0)"); // Comment form to avoid actual instruction issues
+        asm!("nop // V7:6.w = vadd(V5:4.w, V3:2.w)"); // With type suffixes
+
+        // Predicate register pairs
+        asm!("nop // p1:0 = vcmpb.eq(V1:0, V3:2)"); // Comment form
+
+        // Mixed with actual labels should still trigger for the labels
+        asm!("label1: r7:6 = combine(#2, #3)"); //~ ERROR avoid using named labels
+
+        // Regular labels should still trigger
+        asm!("hexagon_label: nop"); //~ ERROR avoid using named labels
+    }
+}