[PR68432 07/22] Use code,alternative attributes for alpha

[Richard Sandiford]

Tested as described in the covering note.  I plan to commit this as obvious
if the prerequisites are approved.

gcc/
        * config/alpha/alpha.md (isa): Turn into a code,alternative
        attribute.
        (enabled): Likewise.

diff --git a/gcc/config/alpha/alpha.md b/gcc/config/alpha/alpha.md
index 5068f60..7f440d3 100644
--- a/gcc/config/alpha/alpha.md
+++ b/gcc/config/alpha/alpha.md
@@ -196,7 +196,8 @@
 ;; For convenience, conflate ABI issues re loading of addresses with
 ;; an "isa".
 (define_attr "isa" "base,bwx,max,fix,cix,vms,ner,er"
-  (const_string "base"))
+  (const_string "base")
+  "code,alternative")
 
 (define_attr "enabled" ""
   (cond [(eq_attr "isa" "bwx") (symbol_ref "TARGET_BWX")
@@ -207,7 +208,8 @@
         (eq_attr "isa" "ner")  (symbol_ref "!TARGET_EXPLICIT_RELOCS")
         (eq_attr "isa" "er")   (symbol_ref "TARGET_EXPLICIT_RELOCS")
        ]
-       (const_int 1)))
+       (const_int 1))
+  "code,alternative")
 
 ;; Include scheduling descriptions.