Electrical computers and digital processing systems: processing – Processing control – Specialized instruction processing in support of testing,...
Reexamination Certificate
1999-06-24
2004-07-13
Tsai, Henry W. H. (Department: 2183)
Electrical computers and digital processing systems: processing
Processing control
Specialized instruction processing in support of testing,...
C712S220000, C703S022000
Reexamination Certificate
active
06763452
ABSTRACT:
BACKGROUND
The invention relates to execution of instructions for a computer of a first computer architecture on a computer of a second, different architecture.
Each instruction for execution by a computer is represented as a binary number stored in the computer's memory. Each different architecture of computer represents instructions differently. For instance, when a given instruction, a given binary number, is executed by an IBM System/360 computer, an IBM System/38, an IBM AS/400, an IBM PC, and an IBM PowerPC, the five computers will typically perform five completely different operations, even though all five are manufactured by the same company. This correspondence between the binary representation of a computer's instructions and the actions taken by the computer in response is called the Instruction Set Architecture (ISA).
A program coded in the binary ISA for a particular computer family is often called simply “a binary.” Commercial software is typically distributed in binary form. The incompatibility noted in the previous paragraph means that programs distributed in binary form for one architecture generally do not run on computers of another. Accordingly, computer users are extremely reluctant to change from one architecture to another, and computer manufacturers are narrowly constrained in modifying their computer architectures.
A computer most naturally executes programs coded in its native ISA, the ISA of the architectural family for which the computer is a member. Several methods are known for executing binaries originally coded for computers of another, non-native, ISA. In hardware emulation, the computer has hardware specifically directed to executing the non-native instructions. Emulation is typically controlled by a mode bit, an electronic switch: when a non-native binary is to be executed, a special instruction in the emulating computer sets the mode bit and transfers control to the non-native binary. When the non-native program exits, the mode bit is reset to specify that subsequent instructions are to be interpreted in the native ISA. Typically, in an emulator, native and non-native instructions are stored in different address spaces. A second alternative uses a simulator (also sometimes known as an “interpreter”), a program running on the computer that models a computer of the non-native architecture. A simulator sequentially fetches instructions of the non-native binary, determines the meaning of each instruction in turn, and simulates its effect in a software model of the non-native computer. Again, a simulator typically stores native and non-native instructions in distinct address spaces. (The terms “emulation” and “simulation” are not as uniformly applied throughout the industry as might be suggested by the definitions implied here.) In a third alternative, binary translation, a translator program takes the non-native binary (either a whole program or a program fragment) as input, and processes it to produce as output a corresponding binary in the native instruction set (a “native binary”) that runs directly on the computer.
Typically, an emulator is found in a newer computer for emulation of an older computer architecture from the same manufacturer, as a transition aid to customers. Simulators are provided for the same purpose, and also by independent software vendors for use by customers who simply want access to software that is only available in binary form for a machine that the customer does not own. By whatever technique, non-native execution is slower than native execution, and a non-native program has access to only a portion of the resources available to a native program.
Known methods of profiling the behavior of a computer or of a computer program include the following. In one known profiling method, the address range occupied by a program is divided into a number of ranges, and a timer goes off from time to time. A software profile analyzer figures out the address at which the program was executing, and increments a counter corresponding to the range that embraces the address. After a time, the counters will indicate that some ranges are executed a great deal, and some are barely executed at all. In another known profiling method, counters are generated into the binary text of a program by the compiler. These compiler-generated counters may count the number of times a given region is executed, or may count the number of times a given execution point is passed or a given branch is taken.
SUMMARY
In general, in a first aspect, the invention features a computer with an instruction processor designed to execute instructions of first and second instruction sets, a memory for storage of a program, a table of entries corresponding to the pages, a switch, a transition handler, and a history record. The memory is divided into pages for management by a virtual memory manager. The program is coded in instructions of the first and second instruction sets and uses first and second data storage conventions. The switch is responsive to a first flag value stored in each table entry, and controls the instruction processor to interpret instructions under, alternately, the first or second instruction set as directed by the first flag value of the table entry corresponding to an instruction's memory page. The transition handler is designed to recognize when program execution has transferred from a page of instructions using the first data storage convention to a page of instructions using the second data storage convention, as indicated by second flag values stored in table entries corresponding to the respective pages, and in response to the recognition, to adjust a data storage configuration of the computer from the first storage convention to the second data storage convention. The history record is designed to provide to the transition handler a record of a classification of a recently-executed instruction.
In a second aspect, the invention features a method, and a computer for performance of the method. Instruction data are fetched from first and second regions of a single address space of the memory of a computer. The instructions of the first and second regions are coded for execution by computer of first and second architectures or following first and second data storage conventions, respectively. The memory regions have associated first and second indicator elements, the indicator elements each having a value indicating the architecture or data storage convention under which instructions from the associated region are to be executed. When execution of the instruction data flows from the first region to the second, the computer is adapted for execution in the second architecture or convention.
In a third aspect, the invention features a method, and a computer for performance of the method. Instructions are stored in pages of a computer memory managed by a virtual memory manager. The instruction data of the pages are coded for execution by, respectively, computers of two different architectures and/or under two different execution conventions. In association with pages of the memory are stored corresponding indicator elements indicating the architecture or convention in which the instructions of the pages are to be executed. Instructions from the pages are executed in a common processor, the processor designed, responsive to the page indicator elements, to execute instructions in the architecture or under the convention indicated by the indicator element corresponding to the instruction's page.
In a fourth aspect, the invention features a microprocessor chip. An instruction unit of the chip is configured to fetch instructions from a memory managed by the virtual memory manager, and configured to execute instructions coded for first and second different computer architectures or coded to implement first and second different data storage conventions. The microprocessor chip is designed (a) to retrieve indicator elements stored in association with respective pages of the memory, each indicator element indicating the architecture or c
Hohensee Paul H.
Purcell Stephen C.
Reese David L.
Van Dyke Korbin S.
Yates, Jr. John S.
ATI International SRL
Boundy David E.
Tsai Henry W. H.
Willkie Farr & Gallagher LLP
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