cpu: Enable tuning for i686-linux.

* gnu/packages/gcc.scm (gcc-7, gcc-10, gcc-11, gcc-12, gcc-13)
[properties]: In compiler-cpu-architectures use the
x86_64-micro-architectures list for i686.
* guix/cpu.scm (cpu->gcc-architecture): Expand the x86_64 case to also
support i686.

Change-Id: I0b820ceb715960db5e702814fa278dc8c619a836

gnu/packages/gcc.scm

@@ -673,6 +673,7 @@ It also includes runtime support libraries for these languages.")
      `((compiler-cpu-architectures
         ("aarch64" ,@%gcc-7.5-aarch64-micro-architectures)
         ("armhf" ,@%gcc-7.5-armhf-micro-architectures)
+        ("i686" ,@%gcc-7.5-x86_64-micro-architectures)
         ("x86_64" ,@%gcc-7.5-x86_64-micro-architectures))
        ,@(package-properties gcc-6)))))
 
@@ -729,6 +730,7 @@ It also includes runtime support libraries for these languages.")
     `((compiler-cpu-architectures
        ("aarch64" ,@%gcc-10-aarch64-micro-architectures)
        ("armhf" ,@%gcc-10-armhf-micro-architectures)
+       ("i686" ,@%gcc-10-x86_64-micro-architectures)
        ("x86_64" ,@%gcc-10-x86_64-micro-architectures))
       ,@(package-properties gcc-8)))))
 
@@ -764,6 +766,7 @@ It also includes runtime support libraries for these languages.")
     `((compiler-cpu-architectures
        ("aarch64" ,@%gcc-11-aarch64-micro-architectures)
        ("armhf" ,@%gcc-11-armhf-micro-architectures)
+       ("i686" ,@%gcc-11-x86_64-micro-architectures)
        ("x86_64" ,@%gcc-11-x86_64-micro-architectures))
       ,@(package-properties gcc-8)))))
 
@@ -786,6 +789,7 @@ It also includes runtime support libraries for these languages.")
     `((compiler-cpu-architectures
        ("aarch64" ,@%gcc-12-aarch64-micro-architectures)
        ("armhf" ,@%gcc-12-armhf-micro-architectures)
+       ("i686" ,@%gcc-12-x86_64-micro-architectures)
        ("x86_64" ,@%gcc-12-x86_64-micro-architectures))
       ,@(package-properties gcc-11)))))
 
@@ -808,6 +812,7 @@ It also includes runtime support libraries for these languages.")
      `((compiler-cpu-architectures
         ("aarch64" ,@%gcc-13-aarch64-micro-architectures)
         ("armhf" ,@%gcc-13-armhf-micro-architectures)
+        ("i686" ,@%gcc-13-x86_64-micro-architectures)
         ("x86_64" ,@%gcc-13-x86_64-micro-architectures))
        ,@(package-properties gcc-11)))))
 

guix/cpu.scm

@@ -113,7 +113,7 @@
   "Return the architecture name, suitable for GCC's '-march' flag, that
 corresponds to CPU, a record as returned by 'current-cpu'."
   (match (cpu-architecture cpu)
-    ("x86_64"
+    ((or "x86_64" "i686")
      ;; Transcribed from GCC's 'host_detect_local_cpu' in driver-i386.cc.
      (letrec-syntax ((if-flags (syntax-rules (=>)
                                  ((_)
@@ -200,7 +200,9 @@ corresponds to CPU, a record as returned by 'current-cpu'."
 
          ;; TODO: Recognize CENTAUR/CYRIX/NSC?
 
-         "x86-64")))
+         (match (cpu-architecture cpu)
+           ("x86_64" "x86-64")
+           (_ "generic")))))
     ("aarch64"
      ;; Transcribed from GCC's list of aarch64 processors in aarch64-cores.def
      ;; What to do with big.LITTLE cores?