exec: reintroduce MemoryRegion caching

MemoryRegionCache was reverted to "normal" address_space_* operations
for 2.9, due to lack of support for IOMMUs.  Reinstate the
optimizations, caching only the IOMMU translation at address_cache_init
but not the IOMMU lookup and target AddressSpace translation are not
cached; now that MemoryRegionCache supports IOMMUs, it becomes more widely
applicable too.

The inlined fast path is defined in memory_ldst_cached.inc.h, while the
slow path uses memory_ldst.inc.c as before.  The smaller fast path causes
a little code size reduction in MemoryRegionCache users:

    hw/virtio/virtio.o text size before: 32373
    hw/virtio/virtio.o text size after: 31941

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/exec/memory_ldst_cached.inc.h

@@ -0,0 +1,108 @@
+/*
+ *  Memory access templates for MemoryRegionCache
+ *
+ *  Copyright (c) 2018 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#define ADDRESS_SPACE_LD_CACHED(size) \
+    glue(glue(address_space_ld, size), glue(ENDIANNESS, _cached))
+#define ADDRESS_SPACE_LD_CACHED_SLOW(size) \
+    glue(glue(address_space_ld, size), glue(ENDIANNESS, _cached_slow))
+#define LD_P(size) \
+    glue(glue(ld, size), glue(ENDIANNESS, _p))
+
+static inline uint32_t ADDRESS_SPACE_LD_CACHED(l)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 4 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(l)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(l)(cache, addr, attrs, result);
+    }
+}
+
+static inline uint64_t ADDRESS_SPACE_LD_CACHED(q)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 8 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(q)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(q)(cache, addr, attrs, result);
+    }
+}
+
+static inline uint32_t ADDRESS_SPACE_LD_CACHED(uw)(MemoryRegionCache *cache,
+    hwaddr addr, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 2 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        return LD_P(uw)(cache->ptr + addr);
+    } else {
+        return ADDRESS_SPACE_LD_CACHED_SLOW(uw)(cache, addr, attrs, result);
+    }
+}
+
+#undef ADDRESS_SPACE_LD_CACHED
+#undef ADDRESS_SPACE_LD_CACHED_SLOW
+#undef LD_P
+
+#define ADDRESS_SPACE_ST_CACHED(size) \
+    glue(glue(address_space_st, size), glue(ENDIANNESS, _cached))
+#define ADDRESS_SPACE_ST_CACHED_SLOW(size) \
+    glue(glue(address_space_st, size), glue(ENDIANNESS, _cached_slow))
+#define ST_P(size) \
+    glue(glue(st, size), glue(ENDIANNESS, _p))
+
+static inline void ADDRESS_SPACE_ST_CACHED(l)(MemoryRegionCache *cache,
+    hwaddr addr, uint32_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 4 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(l)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(l)(cache, addr, val, attrs, result);
+    }
+}
+
+static inline void ADDRESS_SPACE_ST_CACHED(w)(MemoryRegionCache *cache,
+    hwaddr addr, uint32_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 2 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(w)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(w)(cache, addr, val, attrs, result);
+    }
+}
+
+static inline void ADDRESS_SPACE_ST_CACHED(q)(MemoryRegionCache *cache,
+    hwaddr addr, uint64_t val, MemTxAttrs attrs, MemTxResult *result)
+{
+    assert(addr < cache->len && 8 <= cache->len - addr);
+    if (likely(cache->ptr)) {
+        ST_P(q)(cache->ptr + addr, val);
+    } else {
+        ADDRESS_SPACE_ST_CACHED_SLOW(q)(cache, addr, val, attrs, result);
+    }
+}
+
+#undef ADDRESS_SPACE_ST_CACHED
+#undef ADDRESS_SPACE_ST_CACHED_SLOW
+#undef ST_P
+
+#undef ENDIANNESS