From 276f3e9535e72c8e9764b5f7369e1fa9eb055055 Mon Sep 17 00:00:00 2001 From: Gabe Black Date: Fri, 25 May 2012 00:54:39 -0700 Subject: [PATCH] CPU: Simplify the implementation of the decode cache. Also reorganize it to make it more amenable to being rearranged later. --- src/cpu/decode_cache.hh | 89 +++++++++++++++-------------------------- 1 file changed, 32 insertions(+), 57 deletions(-) diff --git a/src/cpu/decode_cache.hh b/src/cpu/decode_cache.hh index 1bff315d1..6ed820332 100644 --- a/src/cpu/decode_cache.hh +++ b/src/cpu/decode_cache.hh @@ -48,45 +48,8 @@ class DecodeCache /// Hash of decoded instructions. typedef m5::hash_map 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; } }; -- 2.30.2