[PATCH v2 1/2] target/ppc/cpu_init: Simplify the setup of the TLBxCFG SPR registers

[Thomas Huth <thuth@redhat.com>]

From: Thomas Huth <thuth@redhat.com>

The next commit is going to remove init_proc_e200(), which is one of
the two calling sites of register_BookE206_sprs(). This causes recent
versions of GCC to inline the register_BookE206_sprs() function into
the other only remaining calling site, init_proc_e500(), which in
turn causes some false-positives compiler warnings:

 In file included from ../../devel/qemu/target/ppc/cpu_init.c:46:
 In function ‘register_BookE206_sprs’,
     inlined from ‘init_proc_e500’ at ../../devel/qemu/target/ppc/cpu_init.c:2910:5:
 ../../devel/qemu/target/ppc/cpu_init.c:897:29: error:
  array subscript 3 is outside array bounds of ‘uint32_t[2]’ {aka ‘unsigned int[2]’}
  [-Werror=array-bounds=]
   897 |                      tlbncfg[3]);
       |                      ~~~~~~~^~~
 ../../devel/qemu/target/ppc/spr_common.h:61:39: note: in definition of macro ‘spr_register_kvm_hv’
    61 |                   KVM_ARG(one_reg_id) initial_value)
       |                                       ^~~~~~~~~~~~~
 ../../devel/qemu/target/ppc/spr_common.h:77:5: note: in expansion of macro ‘spr_register_kvm’
    77 |     spr_register_kvm(env, num, name, uea_read, uea_write,                    \
       |     ^~~~~~~~~~~~~~~~
 ../../devel/qemu/target/ppc/cpu_init.c:894:9: note: in expansion of macro ‘spr_register’
   894 |         spr_register(env, SPR_BOOKE_TLB3CFG, "TLB3CFG",
       |         ^~~~~~~~~~~~
 ../../devel/qemu/target/ppc/cpu_init.c: In function ‘init_proc_e500’:
 ../../devel/qemu/target/ppc/cpu_init.c:2809:14: note: at offset 12 into object ‘tlbncfg’ of size 8
  2809 |     uint32_t tlbncfg[2];
       |              ^~~~~~~
 cc1: all warnings being treated as errors

init_proc_e500() only defines "uint32_t tlbncfg[2];", but it is OK since
it also sets "env->nb_ways = 2", so the code that GCC warns about in
register_BookE206_sprs() is never reached. Unfortunately, GCC is not smart
enough to see this, so it emits these warnings.

To fix it, let's simplify the code in register_BookE206_sprs() a little
bit to set up the SPRs in a loop, so we don't reference the tlbncfg[3]
entry directly anymore.

Signed-off-by: Thomas Huth <thuth@redhat.com>
---
 target/ppc/cpu_init.c | 38 ++++++++++++--------------------------
 1 file changed, 12 insertions(+), 26 deletions(-)

diff --git a/target/ppc/cpu_init.c b/target/ppc/cpu_init.c
index 3aa3aefc136..12c645699e8 100644
--- a/target/ppc/cpu_init.c
+++ b/target/ppc/cpu_init.c
@@ -850,6 +850,13 @@ static void register_BookE206_sprs(CPUPPCState *env, uint32_t mas_mask,
         SPR_BOOKE_MAS0, SPR_BOOKE_MAS1, SPR_BOOKE_MAS2, SPR_BOOKE_MAS3,
         SPR_BOOKE_MAS4, SPR_BOOKE_MAS5, SPR_BOOKE_MAS6, SPR_BOOKE_MAS7,
     };
+    const char *tlbcfg_names[4] = {
+        "TLB0CFG", "TLB1CFG", "TLB2CFG", "TLB3CFG",
+    };
+    const int tlbcfg_sprn[4] = {
+        SPR_BOOKE_TLB0CFG, SPR_BOOKE_TLB1CFG,
+        SPR_BOOKE_TLB2CFG, SPR_BOOKE_TLB3CFG,
+    };
     int i;
 
     /* TLB assist registers */
@@ -889,34 +896,13 @@ static void register_BookE206_sprs(CPUPPCState *env, uint32_t mas_mask,
                  SPR_NOACCESS, SPR_NOACCESS,
                  &spr_read_generic, SPR_NOACCESS,
                  mmucfg);
-    switch (env->nb_ways) {
-    case 4:
-        spr_register(env, SPR_BOOKE_TLB3CFG, "TLB3CFG",
-                     SPR_NOACCESS, SPR_NOACCESS,
-                     &spr_read_generic, SPR_NOACCESS,
-                     tlbncfg[3]);
-        /* Fallthru */
-    case 3:
-        spr_register(env, SPR_BOOKE_TLB2CFG, "TLB2CFG",
-                     SPR_NOACCESS, SPR_NOACCESS,
-                     &spr_read_generic, SPR_NOACCESS,
-                     tlbncfg[2]);
-        /* Fallthru */
-    case 2:
-        spr_register(env, SPR_BOOKE_TLB1CFG, "TLB1CFG",
-                     SPR_NOACCESS, SPR_NOACCESS,
-                     &spr_read_generic, SPR_NOACCESS,
-                     tlbncfg[1]);
-        /* Fallthru */
-    case 1:
-        spr_register(env, SPR_BOOKE_TLB0CFG, "TLB0CFG",
+
+    assert(env->nb_ways <= ARRAY_SIZE(tlbcfg_names));
+    for (i = 0; i < env->nb_ways; i++) {
+        spr_register(env, tlbcfg_sprn[i], tlbcfg_names[i],
                      SPR_NOACCESS, SPR_NOACCESS,
                      &spr_read_generic, SPR_NOACCESS,
-                     tlbncfg[0]);
-        /* Fallthru */
-    case 0:
-    default:
-        break;
+                     tlbncfg[i]);
     }
 #endif
 }
-- 
2.51.0