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CPU: Simplify the implementation of the decode cache.

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Also reorganize it to make it more amenable to being rearranged later.
This commit is contained in:
Gabe Black 2012-05-25 00:54:39 -07:00
parent 82a228bd43
commit 276f3e9535
1 changed files with 32 additions and 57 deletions
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89
src/cpu/decode_cache.hh
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@ -48,45 +48,8 @@ class DecodeCache
/// Hash of decoded instructions.
typedef m5::hash_map<ExtMachInst, StaticInstPtr> InstMap;
InstMap instMap;
/// A table of instructions which are already been decoded, indexed by
/// page offset.
class DecodePage
{
protected:
StaticInstPtr instructions[TheISA::PageBytes];
// A helper function to compute the index of an address in the table.
Addr offset(Addr addr) { return addr & (TheISA::PageBytes - 1); }
public:
/// Decode the given instruction. First attempt to find it in the
/// table, then in the generic decode cache, and finally call the
/// actual decode function.
///
/// @param mach_inst The predecoded instruction to decode.
/// @param addr The address the instruction came from.
/// @param cache A cache of already decoded instructions.
/// @retval The decoded instruction object.
StaticInstPtr
decode(const ExtMachInst &mach_inst, Addr addr, InstMap &instMap)
{
StaticInstPtr si = instructions[offset(addr)];
if (si && (si->machInst == mach_inst)) {
return si;
}
InstMap::iterator iter = instMap.find(mach_inst);
if (iter != instMap.end()) {
si = iter->second;
} else {
si = decodeInstFunc(mach_inst);
instMap[mach_inst] = si;
}
instructions[offset(addr)] = si;
return si;
}
struct DecodePage {
StaticInstPtr insts[TheISA::PageBytes];
};
/// A store of DecodePages. Basically a slightly smarter hash_map.
@ -107,6 +70,14 @@ class DecodeCache
recent[0] = recentest;
}
void
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);
}
public:
/// Constructor
DecodePages()
@ -119,7 +90,7 @@ class DecodeCache
/// actually look in the hash_map.
/// @param addr The address to look up.
DecodePage *
findPage(Addr addr)
getPage(Addr addr)
{
Addr page_addr = addr & ~(TheISA::PageBytes - 1);
@ -142,16 +113,10 @@ class DecodeCache
return it->second;
}
// Didn't find it so return NULL.
return NULL;
}
void
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);
// Didn't find an existing page, so add a new one.
DecodePage *newPage = new DecodePage;
addPage(page_addr, newPage);
return newPage;
}
} decodePages;
@ -163,16 +128,26 @@ class DecodeCache
decode(ExtMachInst mach_inst, Addr addr)
{
// Try to find a matching address based table of instructions.
DecodePage *page = decodePages.findPage(addr);
if (!page) {
// Nothing was found, so create a new one.
page = new DecodePage;
decodePages.addPage(addr, page);
}
DecodePage *page = decodePages.getPage(addr);
// Use the table to decode the instruction. It will fall back to other
// mechanisms if it needs to.
return page->decode(mach_inst, addr, instMap);
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 = decodeInstFunc(mach_inst);
instMap[mach_inst] = si;
page->insts[offset] = si;
return si;
}
};