ISA: Make the decode function part of the ISA's decoder.

1 files changed, 113 insertions, 0 deletions

diff --git a/src/cpu/decode_cache.cc b/src/cpu/decode_cache.cc
new file mode 100644
index 000000000..636bf9284
--- /dev/null
+++ b/src/cpu/decode_cache.cc
@@ -0,0 +1,113 @@
+/*
+ * Copyright (c) 2011-2012 Google
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ * Authors: Gabe Black
+ */
+
+#include "arch/decoder.hh"
+#include "arch/isa_traits.hh"
+#include "arch/types.hh"
+#include "base/hashmap.hh"
+#include "config/the_isa.hh"
+#include "cpu/static_inst.hh"
+
+void
+DecodeCache::DecodePages::update(PageIt recentest)
+{
+    recent[1] = recent[0];
+    recent[0] = recentest;
+}
+
+void
+DecodeCache::DecodePages::addPage(Addr addr, DecodePage *page)
+{
+    Addr page_addr = addr & ~(TheISA::PageBytes - 1);
+    typename PageMap::value_type to_insert(page_addr, page);
+    update(pageMap.insert(to_insert).first);
+}
+
+DecodeCache::DecodePages::DecodePages()
+{
+    recent[0] = recent[1] = pageMap.end();
+}
+
+DecodeCache::DecodePage *
+DecodeCache::DecodePages::getPage(Addr addr)
+{
+    Addr page_addr = addr & ~(TheISA::PageBytes - 1);
+
+    // Check against recent lookups.
+    if (recent[0] != pageMap.end()) {
+        if (recent[0]->first == page_addr)
+            return recent[0]->second;
+        if (recent[1] != pageMap.end() &&
+                recent[1]->first == page_addr) {
+            update(recent[1]);
+            // recent[1] has just become recent[0].
+            return recent[0]->second;
+        }
+    }
+
+    // Actually look in the has_map.
+    PageIt it = pageMap.find(page_addr);
+    if (it != pageMap.end()) {
+        update(it);
+        return it->second;
+    }
+
+    // Didn't find an existing page, so add a new one.
+    DecodePage *newPage = new DecodePage;
+    addPage(page_addr, newPage);
+    return newPage;
+}
+
+StaticInstPtr
+DecodeCache::decode(TheISA::Decoder *decoder,
+        ExtMachInst mach_inst, Addr addr)
+{
+    // Try to find a matching address based table of instructions.
+    DecodePage *page = decodePages.getPage(addr);
+
+    // Use the table to decode the instruction. It will fall back to other
+    // mechanisms if it needs to.
+    Addr offset = addr & (TheISA::PageBytes - 1);
+    StaticInstPtr si = page->insts[offset];
+    if (si && (si->machInst == mach_inst))
+        return si;
+
+    InstMap::iterator iter = instMap.find(mach_inst);
+    if (iter != instMap.end()) {
+        si = iter->second;
+        page->insts[offset] = si;
+        return si;
+    }
+
+    si = decoder->decodeInst(mach_inst);
+    instMap[mach_inst] = si;
+    page->insts[offset] = si;
+    return si;
+}