International Business Machines Corporation

Vadim Eisenberg

Moshe Klausner

Gad Haber

Maxim Gurevich

A method for improving program performance including reordering a global data area of a program and for each load instruction referencing global variables within range of the immediate part of an add immediate instruction from a TOC anchor, replacing the load instruction with an add immediate instruction. The method may further include placing a TOC at the top, or within a predetermined distance from the top, of the global data area. The method may also include placing the global variables after the TOC, wherein more frequently referenced global variable are closer to the TOC than less frequently referenced global variables. Also, the method may further include placing in run-time order, groups of the global variables that frequently follow each other in run-time.

Reducing load instructions via global data reordering

A method for post-link code optimization by identifying cold caller functions of a hot callee function, and percolating store and restore instructions with respect to non-volatile registers from the callee function to the caller function.

Percolating hot function store/restores to colder calling functions

A post-link optimization method for renaming non-volatile registers with unused volatile registers, then removing the non-volatile register store/restore instructions from a function prolog/epilog. The volatile registers are saved before each function call and restored immediately afterwards. The optimization method is worthwhile if all of the call instructions are rarely invoked relative to the function prolog/epilog. The method requires that the hot function be disassembled, but does not require the full control flow graph.

Eliminating store/restores within hot function prolog/epilogs using volatile registers

A post-link optimization method for removing non-volatile register store/restore instructions from a hot function prolog/epilog, when the non-volatile register is referenced only in cold sections of code within the hot function. The method requires that the hot function be disassembled, but does not require the full control flow graph.

Eliminating cold register store/restores within hot function prolog/epilogs

A method for code optimization includes disassembling object code that has been compiled and linked, and identifying a function in the disassembled code, the function including store and restore instructions with respect to a register. The disassembled code is analyzed to locate a call to the function followed by an instruction to kill the register. The code is modified so as to eliminate the store instruction from the function when the function is invoked by the located call.

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Haifa, Israel

Vadim Eisenberg