[emacs] Highlight 'zeroext' and 'signext' keyword as an attribute

[goldstein.w.n]

Summary

Seems natural to highlight 'zeroext' and 'signext' along with other attributes
like 'nonnull', 'noundef', etc..

[nikic]

Also add signext?

[goldstein.w.n]

add signext

[goldstein.w.n]

In D154571#4476128, @nikic wrote:

Also add signext?

Done (just tend to add as I notice).

Out of curiosity, do you use emacs or are you just a kind soul to review this?

[nikic]

LGTM, but the patch description refers to the wrong attributes.

Out of curiosity, do you use emacs or are you just a kind soul to review this?

Nope, I use vim :)

llvm/utils/emacs/llvm-mode.el

29–30

The attributes here are (mostly) sorted, so maybe but signext next to shadowcallstack?

[goldstein.w.n]

Sort attrs

llvm/utils/emacs/llvm-mode.el

(let ((table (make-syntax-table)))
     (modify-syntax-entry ?\n "> " table)
     table)
   "Syntax table used while in LLVM mode.")
 
 (defvar llvm-font-lock-keywords
   (list
    ;; Attributes
    `(,(regexp-opt
-       '("alwaysinline" "argmemonly" "allocsize" "builtin" "cold" "convergent" "dereferenceable" "dereferenceable_or_null" "hot" "inaccessiblememonly"
+       '("alwaysinline" "argmemonly" "allocsize" "builtin" "cold" "convergent" "dereferenceable" "dereferenceable_or_null" "hot" "immarg" "inaccessiblememonly"
          "inaccessiblemem_or_argmemonly" "inalloca" "inlinehint" "jumptable" "minsize" "mustprogress" "naked" "nobuiltin" "nonnull" "nocapture"
          "nocallback" "nocf_check" "noduplicate" "nofree" "noimplicitfloat" "noinline" "nomerge" "nonlazybind" "noprofile" "noredzone" "noreturn"
          "norecurse" "nosync" "noundef" "nounwind" "nosanitize_bounds" "nosanitize_coverage" "null_pointer_is_valid" "optforfuzzing" "optnone" "optsize" "preallocated" "readnone" "readonly" "returned" "returns_twice"
-         "shadowcallstack" "speculatable" "speculative_load_hardening" "ssp" "sspreq" "sspstrong" "safestack" "sanitize_address" "sanitize_hwaddress" "sanitize_memtag"
-         "sanitize_thread" "sanitize_memory" "strictfp" "swifterror" "uwtable" "vscale_range" "willreturn" "writeonly" "immarg") 'symbols) . font-lock-constant-face)
+         "shadowcallstack" "signext" "speculatable" "speculative_load_hardening" "ssp" "sspreq" "sspstrong" "safestack" "sanitize_address" "sanitize_hwaddress" "sanitize_memtag"
+         "sanitize_thread" "sanitize_memory" "strictfp" "swifterror" "uwtable" "vscale_range" "willreturn" "writeonly" "zeroext") 'symbols) . font-lock-constant-face)
    ;; Variables
    '("%[-a-zA-Z$._][-a-zA-Z$._0-9]*" . font-lock-variable-name-face)
    ;; Labels
    '("[-a-zA-Z$._0-9]+:" . font-lock-variable-name-face)
    ;; Unnamed variable slots
    '("%[-]?[0-9]+" . font-lock-variable-name-face)
    ;; Types
    `(,(regexp-opt