hw/audio/intel-hda: Use memory region alias to reduce .rodata by 4.34MB

The intel-hda model uses an array of register indexed by the
register address. This array also contains a pair of aliased
registers at offset 0x2000. This creates a huge hole in the
array, which ends up eating 4.6MiB of .rodata (size reported
on x86_64 host, building with --extra-cflags=-Os).

By using a memory region alias, we reduce this array to 132kB.

Before:

  (qemu) info mtree
    00000000febd4000-00000000febd7fff (prio 1, i/o): intel-hda

After:

  (qemu) info mtree
    00000000febd4000-00000000febd7fff (prio 1, i/o): intel-hda
    00000000febd4000-00000000febd7fff (prio 1, i/o): intel-hda-container
      00000000febd4000-00000000febd5fff (prio 0, i/o): intel-hda
      00000000febd6000-00000000febd7fff (prio 0, i/o): alias intel-hda-alias @intel-hda 0000000000000000-0000000000001fff

Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/audio/intel-hda.c

@@ -181,7 +181,9 @@ struct IntelHDAState {
     IntelHDAStream st[8];
 
     /* state */
+    MemoryRegion container;
     MemoryRegion mmio;
+    MemoryRegion alias;
     uint32_t rirb_count;
     int64_t wall_base_ns;
 
@@ -670,12 +672,6 @@ static const struct IntelHDAReg regtab[] = {
         .offset   = offsetof(IntelHDAState, wall_clk),
         .rhandler = intel_hda_get_wall_clk,
     },
-    [ ICH6_REG_WALLCLK + 0x2000 ] = {
-        .name     = "WALLCLK(alias)",
-        .size     = 4,
-        .offset   = offsetof(IntelHDAState, wall_clk),
-        .rhandler = intel_hda_get_wall_clk,
-    },
 
     /* dma engine */
     [ ICH6_REG_CORBLBASE ] = {
@@ -837,12 +833,6 @@ static const struct IntelHDAReg regtab[] = {
         .size     = 4,                                                \
         .offset   = offsetof(IntelHDAState, st[_i].lpib),             \
     },                                                                \
-    [ ST_REG(_i, ICH6_REG_SD_LPIB) + 0x2000 ] = {                     \
-        .stream   = _i,                                               \
-        .name     = _t stringify(_i) " LPIB(alias)",                  \
-        .size     = 4,                                                \
-        .offset   = offsetof(IntelHDAState, st[_i].lpib),             \
-    },                                                                \
     [ ST_REG(_i, ICH6_REG_SD_CBL) ] = {                               \
         .stream   = _i,                                               \
         .name     = _t stringify(_i) " CBL",                          \
@@ -1125,9 +1115,15 @@ static void intel_hda_realize(PCIDevice *pci, Error **errp)
         error_free(err);
     }
 
+    memory_region_init(&d->container, OBJECT(d),
+                       "intel-hda-container", 0x4000);
     memory_region_init_io(&d->mmio, OBJECT(d), &intel_hda_mmio_ops, d,
-                          "intel-hda", 0x4000);
-    pci_register_bar(&d->pci, 0, 0, &d->mmio);
+                          "intel-hda", 0x2000);
+    memory_region_add_subregion(&d->container, 0x0000, &d->mmio);
+    memory_region_init_alias(&d->alias, OBJECT(d), "intel-hda-alias",
+                             &d->mmio, 0, 0x2000);
+    memory_region_add_subregion(&d->container, 0x2000, &d->alias);
+    pci_register_bar(&d->pci, 0, 0, &d->container);
 
     hda_codec_bus_init(DEVICE(pci), &d->codecs, sizeof(d->codecs),
                        intel_hda_response, intel_hda_xfer);