Make named asm_labels lint not trigger on hexagon register spans

Author: androm3da

compiler/rustc_lint/src/builtin.rs

@@ -2875,6 +2875,71 @@ 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.
+pub fn is_hexagon_register_span(possible_label: &str) -> bool {
+    // Extract the full register span from the context
+    if let Some(colon_idx) = possible_label.find(':') {
+        let after_colon = &possible_label[colon_idx + 1..];
+        is_hexagon_register_span_impl(&possible_label[..colon_idx], after_colon)
+    } else {
+        false
+    }
+}
+
+/// Helper function for use within the lint when we have statement context.
+fn is_hexagon_register_span_context(
+    possible_label: &str,
+    statement: &str,
+    colon_idx: usize,
+) -> bool {
+    // Extract what comes after the colon in the statement
+    let after_colon_start = colon_idx + 1;
+    if after_colon_start >= statement.len() {
+        return false;
+    }
+
+    // Get the part after the colon, up to the next whitespace or special character
+    let after_colon_full = &statement[after_colon_start..];
+    let after_colon = after_colon_full
+        .chars()
+        .take_while(|&c| c.is_ascii_alphanumeric() || c == '.')
+        .collect::<String>();
+
+    is_hexagon_register_span_impl(possible_label, &after_colon)
+}
+
+/// Core implementation for checking hexagon register spans.
+fn is_hexagon_register_span_impl(before_colon: &str, after_colon: &str) -> bool {
+    if before_colon.len() < 1 || after_colon.is_empty() {
+        return false;
+    }
+
+    let mut chars = before_colon.chars();
+    let start = chars.next().unwrap();
+
+    // Must start with a letter (r, V, p, etc.)
+    if !start.is_ascii_alphabetic() {
+        return false;
+    }
+
+    let rest = &before_colon[1..];
+
+    // Check if the part after the first letter is all digits and non-empty
+    if rest.is_empty() || !rest.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 {
@@ -2957,6 +3022,14 @@ 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_context(possible_label, statement, idx)
+                        {
+                            break 'label_loop;
+                        }
+
                         for c in chars {
                             // Inside a template format arg, any character is permitted for the
                             // purposes of label detection because we assume that it can be

compiler/rustc_lint/src/tests.rs

@@ -2,6 +2,7 @@
 
 use rustc_span::{Symbol, create_default_session_globals_then};
 
+use crate::builtin::is_hexagon_register_span;
 use crate::levels::parse_lint_and_tool_name;
 
 #[test]
@@ -27,3 +28,29 @@ fn parse_lint_multiple_path() {
         )
     });
 }
+
+#[test]
+fn test_hexagon_register_span_patterns() {
+    // Valid Hexagon register span patterns
+    assert!(is_hexagon_register_span("r1:0"));
+    assert!(is_hexagon_register_span("r15:14"));
+    assert!(is_hexagon_register_span("V5:4"));
+    assert!(is_hexagon_register_span("V3:2"));
+    assert!(is_hexagon_register_span("V5:4.w"));
+    assert!(is_hexagon_register_span("V3:2.h"));
+    assert!(is_hexagon_register_span("r99:98"));
+    assert!(is_hexagon_register_span("V123:122.whatever"));
+
+    // Invalid patterns - these should be treated as potential labels
+    assert!(!is_hexagon_register_span("label1"));
+    assert!(!is_hexagon_register_span("foo:"));
+    assert!(!is_hexagon_register_span(":0"));
+    assert!(!is_hexagon_register_span("r:0")); // missing digits before colon
+    assert!(!is_hexagon_register_span("r1:")); // missing digits after colon
+    assert!(!is_hexagon_register_span("r1:a")); // non-digit after colon
+    assert!(!is_hexagon_register_span("1:0")); // starts with digit, not letter
+    assert!(!is_hexagon_register_span("r1")); // no colon
+    assert!(!is_hexagon_register_span("r")); // too short
+    assert!(!is_hexagon_register_span("")); // empty
+    assert!(!is_hexagon_register_span("ra:0")); // letter in first digit group
+}

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

@@ -0,0 +1,35 @@
+//@ add-core-stubs
+//@ compile-flags: --target hexagon-unknown-linux-musl -C target-feature=+hvx-length128b
+//@ needs-llvm-components: hexagon
+//@ ignore-backends: gcc
+
+#![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);
+
+        // These patterns look like register spans but test different edge cases
+        // All should NOT trigger the lint as they match valid hexagon register syntax patterns
+        asm!("V5:4 = vaddw(v1:0, v1:0)", options(nostack));  // Uppercase V register pair
+        asm!("v1:0.w = vsub(v1:0.w,v1:0.w):sat", options(nostack));  // Lowercase v with suffix
+
+        // 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
+    }
+}

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

@@ -0,0 +1,21 @@
+error: avoid using named labels in inline assembly
+  --> $DIR/hexagon-register-pairs.rs:30:15
+   |
+LL |         asm!("label1: r7:6 = combine(#2, #3)");
+   |               ^^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information
+   = note: `#[deny(named_asm_labels)]` on by default
+
+error: avoid using named labels in inline assembly
+  --> $DIR/hexagon-register-pairs.rs:33:15
+   |
+LL |         asm!("hexagon_label: nop");
+   |               ^^^^^^^^^^^^^
+   |
+   = help: only local labels of the form `<number>:` should be used in inline asm
+   = note: see the asm section of Rust By Example <https://doc.rust-lang.org/nightly/rust-by-example/unsafe/asm.html#labels> for more information
+
+error: aborting due to 2 previous errors
+