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2016-02-06arch: get rid of dummy var initSteve Reinhardt
MemOperand variables were being initialized to 0 "to avoid 'uninitialized variable' errors" but these no longer seem to be a problem (with the exception of one use case in POWER that is arguably broken and easily fixed here). Getting rid of the initialization is necessary to set up a subsequent patch which extends memory operands to possibly not be scalars, making the '= 0' initialization no longer feasible.
2016-01-17cpu. arch: add initiateMemRead() to ExecContext interfaceSteve Reinhardt
For historical reasons, the ExecContext interface had a single function, readMem(), that did two different things depending on whether the ExecContext supported atomic memory mode (i.e., AtomicSimpleCPU) or timing memory mode (all the other models). In the former case, it actually performed a memory read; in the latter case, it merely initiated a read access, and the read completion did not happen until later when a response packet arrived from the memory system. This led to some confusing things, including timing accesses being required to provide a pointer for the return data even though that pointer was only used in atomic mode. This patch splits this interface, adding a new initiateMemRead() function to the ExecContext interface to replace the timing-mode use of readMem(). For consistency and clarity, the readMemTiming() helper function in the ISA definitions is renamed to initiateMemRead() as well. For x86, where the access size is passed in explicitly, we can also get rid of the data parameter at this level. For other ISAs, where the access size is determined from the type of the data parameter, we have to keep the parameter for that purpose.
2014-10-16arch: Use shared_ptr for all FaultsAndreas Hansson
This patch takes quite a large step in transitioning from the ad-hoc RefCountingPtr to the c++11 shared_ptr by adopting its use for all Faults. There are no changes in behaviour, and the code modifications are mostly just replacing "new" with "make_shared".
2014-05-09arch: teach ISA parser how to split code across filesCurtis Dunham
This patch encompasses several interrelated and interdependent changes to the ISA generation step. The end goal is to reduce the size of the generated compilation units for instruction execution and decoding so that batch compilation can proceed with all CPUs active without exhausting physical memory. The ISA parser (src/arch/isa_parser.py) has been improved so that it can accept 'split [output_type];' directives at the top level of the grammar and 'split(output_type)' python calls within 'exec {{ ... }}' blocks. This has the effect of "splitting" the files into smaller compilation units. I use air-quotes around "splitting" because the files themselves are not split, but preprocessing directives are inserted to have the same effect. Architecturally, the ISA parser has had some changes in how it works. In general, it emits code sooner. It doesn't generate per-CPU files, and instead defers to the C preprocessor to create the duplicate copies for each CPU type. Likewise there are more files emitted and the C preprocessor does more substitution that used to be done by the ISA parser. Finally, the build system (SCons) needs to be able to cope with a dynamic list of source files coming out of the ISA parser. The changes to the SCons{cript,truct} files support this. In broad strokes, the targets requested on the command line are hidden from SCons until all the build dependencies are determined, otherwise it would try, realize it can't reach the goal, and terminate in failure. Since build steps (i.e. running the ISA parser) must be taken to determine the file list, several new build stages have been inserted at the very start of the build. First, the build dependencies from the ISA parser will be emitted to arch/$ISA/generated/inc.d, which is then read by a new SCons builder to finalize the dependencies. (Once inc.d exists, the ISA parser will not need to be run to complete this step.) Once the dependencies are known, the 'Environments' are made by the makeEnv() function. This function used to be called before the build began but now happens during the build. It is easy to see that this step is quite slow; this is a known issue and it's important to realize that it was already slow, but there was no obvious cause to attribute it to since nothing was displayed to the terminal. Since new steps that used to be performed serially are now in a potentially-parallel build phase, the pathname handling in the SCons scripts has been tightened up to deal with chdir() race conditions. In general, pathnames are computed earlier and more likely to be stored, passed around, and processed as absolute paths rather than relative paths. In the end, some of these issues had to be fixed by inserting serializing dependencies in the build. Minor note: For the null ISA, we just provide a dummy inc.d so SCons is never compelled to try to generate it. While it seems slightly wrong to have anything in src/arch/*/generated (i.e. a non-generated 'generated' file), it's by far the simplest solution.
2014-05-09arch: remove inline specifiers on all inst constrs, all ISAsCurtis Dunham
With (upcoming) separate compilation, they are useless. Only link-time optimization could re-inline them, but ideally feedback-directed optimization would choose to do so only for profitable (i.e. common) instructions.
2012-05-25ISA: Make the decode function part of the ISA's decoder.Gabe Black
2012-04-14clang/gcc: Fix compilation issues with clang 3.0 and gcc 4.6Andreas Hansson
This patch addresses a number of minor issues that cause problems when compiling with clang >= 3.0 and gcc >= 4.6. Most importantly, it avoids using the deprecated ext/hash_map and instead uses unordered_map (and similarly so for the hash_set). To make use of the new STL containers, g++ and clang has to be invoked with "-std=c++0x", and this is now added for all gcc versions >= 4.6, and for clang >= 3.0. For gcc >= 4.3 and <= 4.5 and clang <= 3.0 we use the tr1 unordered_map to avoid the deprecation warning. The addition of c++0x in turn causes a few problems, as the compiler is more stringent and adds a number of new warnings. Below, the most important issues are enumerated: 1) the use of namespaces is more strict, e.g. for isnan, and all headers opening the entire namespace std are now fixed. 2) another other issue caused by the more stringent compiler is the narrowing of the embedded python, which used to be a char array, and is now unsigned char since there were values larger than 128. 3) a particularly odd issue that arose with the new c++0x behaviour is found in range.hh, where the operator< causes gcc to complain about the template type parsing (the "<" is interpreted as the beginning of a template argument), and the problem seems to be related to the begin/end members introduced for the range-type iteration, which is a new feature in c++11. As a minor update, this patch also fixes the build flags for the clang debug target that used to be shared with gcc and incorrectly use "-ggdb".
2012-03-26Power: Change bitfield name to avoid conflicts with range_mapAndreas Hansson
This patch changes the name of a bitfield from W to W_FIELD to avoid clashes with W being used as a class (typename) in the templatized range_map. It also changes L to L_FIELD to avoid future problems. The problem manifestes itself when the CPU includes a header that in turn includes range_map.hh. The relevant parts of the decoder are updated.
2011-10-31GCC: Get everything working with gcc 4.6.1.Gabe Black
And by "everything" I mean all the quick regressions.
2011-09-26ISA parser: Use '_' instead of '.' to delimit type modifiers on operands.Gabe Black
By using an underscore, the "." is still available and can unambiguously be used to refer to members of a structure if an operand is a structure, class, etc. This change mostly just replaces the appropriate "."s with "_"s, but there were also a few places where the ISA descriptions where handling the extensions themselves and had their own regular expressions to update. The regular expressions in the isa parser were updated as well. It also now looks for one of the defined type extensions specifically after connecting "_" where before it would look for any sequence of characters after a "." following an operand name and try to use it as the extension. This helps to disambiguate cases where a "_" may legitimately be part of an operand name but not separate the name from the type suffix. Because leaving the "_" and suffix on the variable name still leaves a valid C++ identifier and all extensions need to be consistent in a given context, I considered leaving them on as a breadcrumb that would show what the intended type was for that operand. Unfortunately the operands can be referred to in code templates, the Mem operand in particular, and since the exact type of Mem can be different for different uses of the same template, that broke things.
2011-07-05ISAs: Streamline some spots where Mem is used in the ISA descriptions.Gabe Black
2011-07-05ISA parser: Define operand types with a ctype directly.Gabe Black
2011-07-05ISA parser: Simplify operand type handling.Gabe Black
This change simplifies the code surrounding operand type handling and makes it depend only on the ctype that goes with each operand type. Future changes will allow defining operand types by their ctypes directly, convert the ISAs over to that style of definition, and then remove support for the old style. These changes are to make it easier to use non-builtin types like classes or structures as the type for operands.
2011-07-02ISA: Use readBytes/writeBytes for all instruction level memory operations.Gabe Black
2011-04-15includes: fix up code after sortingNathan Binkert
2011-04-15includes: sort all includesNathan Binkert
2010-12-08POWER: Take advantage of new PCState syntax.Gabe Black
2010-10-31ISA,CPU,etc: Create an ISA defined PC type that abstracts out ISA behaviors.Gabe Black
This change is a low level and pervasive reorganization of how PCs are managed in M5. Back when Alpha was the only ISA, there were only 2 PCs to worry about, the PC and the NPC, and the lsb of the PC signaled whether or not you were in PAL mode. As other ISAs were added, we had to add an NNPC, micro PC and next micropc, x86 and ARM introduced variable length instruction sets, and ARM started to keep track of mode bits in the PC. Each CPU model handled PCs in its own custom way that needed to be updated individually to handle the new dimensions of variability, or, in the case of ARMs mode-bit-in-the-pc hack, the complexity could be hidden in the ISA at the ISA implementation's expense. Areas like the branch predictor hadn't been updated to handle branch delay slots or micropcs, and it turns out that had introduced a significant (10s of percent) performance bug in SPARC and to a lesser extend MIPS. Rather than perpetuate the problem by reworking O3 again to handle the PC features needed by x86, this change was introduced to rework PC handling in a more modular, transparent, and hopefully efficient way. PC type: Rather than having the superset of all possible elements of PC state declared in each of the CPU models, each ISA defines its own PCState type which has exactly the elements it needs. A cross product of canned PCState classes are defined in the new "generic" ISA directory for ISAs with/without delay slots and microcode. These are either typedef-ed or subclassed by each ISA. To read or write this structure through a *Context, you use the new pcState() accessor which reads or writes depending on whether it has an argument. If you just want the address of the current or next instruction or the current micro PC, you can get those through read-only accessors on either the PCState type or the *Contexts. These are instAddr(), nextInstAddr(), and microPC(). Note the move away from readPC. That name is ambiguous since it's not clear whether or not it should be the actual address to fetch from, or if it should have extra bits in it like the PAL mode bit. Each class is free to define its own functions to get at whatever values it needs however it needs to to be used in ISA specific code. Eventually Alpha's PAL mode bit could be moved out of the PC and into a separate field like ARM. These types can be reset to a particular pc (where npc = pc + sizeof(MachInst), nnpc = npc + sizeof(MachInst), upc = 0, nupc = 1 as appropriate), printed, serialized, and compared. There is a branching() function which encapsulates code in the CPU models that checked if an instruction branched or not. Exactly what that means in the context of branch delay slots which can skip an instruction when not taken is ambiguous, and ideally this function and its uses can be eliminated. PCStates also generally know how to advance themselves in various ways depending on if they point at an instruction, a microop, or the last microop of a macroop. More on that later. Ideally, accessing all the PCs at once when setting them will improve performance of M5 even though more data needs to be moved around. This is because often all the PCs need to be manipulated together, and by getting them all at once you avoid multiple function calls. Also, the PCs of a particular thread will have spatial locality in the cache. Previously they were grouped by element in arrays which spread out accesses. Advancing the PC: The PCs were previously managed entirely by the CPU which had to know about PC semantics, try to figure out which dimension to increment the PC in, what to set NPC/NNPC, etc. These decisions are best left to the ISA in conjunction with the PC type itself. Because most of the information about how to increment the PC (mainly what type of instruction it refers to) is contained in the instruction object, a new advancePC virtual function was added to the StaticInst class. Subclasses provide an implementation that moves around the right element of the PC with a minimal amount of decision making. In ISAs like Alpha, the instructions always simply assign NPC to PC without having to worry about micropcs, nnpcs, etc. The added cost of a virtual function call should be outweighed by not having to figure out as much about what to do with the PCs and mucking around with the extra elements. One drawback of making the StaticInsts advance the PC is that you have to actually have one to advance the PC. This would, superficially, seem to require decoding an instruction before fetch could advance. This is, as far as I can tell, realistic. fetch would advance through memory addresses, not PCs, perhaps predicting new memory addresses using existing ones. More sophisticated decisions about control flow would be made later on, after the instruction was decoded, and handed back to fetch. If branching needs to happen, some amount of decoding needs to happen to see that it's a branch, what the target is, etc. This could get a little more complicated if that gets done by the predecoder, but I'm choosing to ignore that for now. Variable length instructions: To handle variable length instructions in x86 and ARM, the predecoder now takes in the current PC by reference to the getExtMachInst function. It can modify the PC however it needs to (by setting NPC to be the PC + instruction length, for instance). This could be improved since the CPU doesn't know if the PC was modified and always has to write it back. ISA parser: To support the new API, all PC related operand types were removed from the parser and replaced with a PCState type. There are two warts on this implementation. First, as with all the other operand types, the PCState still has to have a valid operand type even though it doesn't use it. Second, using syntax like PCS.npc(target) doesn't work for two reasons, this looks like the syntax for operand type overriding, and the parser can't figure out if you're reading or writing. Instructions that use the PCS operand (which I've consistently called it) need to first read it into a local variable, manipulate it, and then write it back out. Return address stack: The return address stack needed a little extra help because, in the presence of branch delay slots, it has to merge together elements of the return PC and the call PC. To handle that, a buildRetPC utility function was added. There are basically only two versions in all the ISAs, but it didn't seem short enough to put into the generic ISA directory. Also, the branch predictor code in O3 and InOrder were adjusted so that they always store the PC of the actual call instruction in the RAS, not the next PC. If the call instruction is a microop, the next PC refers to the next microop in the same macroop which is probably not desirable. The buildRetPC function advances the PC intelligently to the next macroop (in an ISA specific way) so that that case works. Change in stats: There were no change in stats except in MIPS and SPARC in the O3 model. MIPS runs in about 9% fewer ticks. SPARC runs with 30%-50% fewer ticks, which could likely be improved further by setting call/return instruction flags and taking advantage of the RAS. TODO: Add != operators to the PCState classes, defined trivially to be !(a==b). Smooth out places where PCs are split apart, passed around, and put back together later. I think this might happen in SPARC's fault code. Add ISA specific constructors that allow setting PC elements without calling a bunch of accessors. Try to eliminate the need for the branching() function. Factor out Alpha's PAL mode pc bit into a separate flag field, and eliminate places where it's blindly masked out or tested in the PC.
2010-10-22ISA: Simplify various implementations of completeAcc.Gabe Black
2010-03-23cpu: fix exec tracing memory corruption bugSteve Reinhardt
Accessing traceData (to call setAddress() and/or setData()) after initiating a timing translation was causing crashes, since a failed translation could delete the traceData object before returning. It turns out that there was never a need to access traceData after initiating the translation, as the traced data was always available earlier; this ordering was merely historical. Furthermore, traceData->setAddress() and traceData->setData() were being called both from the CPU model and the ISA definition, often redundantly. This patch standardizes all setAddress and setData calls for memory instructions to be in the CPU models and not in the ISA definition. It also moves those calls above the translation calls to eliminate the crashes.
2009-10-27POWER: Add support for the Power ISATimothy M. Jones
This adds support for the 32-bit, big endian Power ISA. This supports both integer and floating point instructions based on the Power ISA Book I v2.06.