International Business Machines Corporation

Nava Arela Aizikowitz

Edward Curtis Prosser

Robert Ralph Roediger

William Jon Schmidt

Roy N Bar-Haim

Liviu Asnash

Ayal Zaks

Vitaly Feldman

Orit Edelstein

Mircea Namolaru

A method and system for identifying calls in a Java package whose targets are guaranteed to belong to the package. According to the method an inheritance graph and access permissions of respective components in the package are determined, both of which are used in combination with the knowledge that the package is seared and signed to determine whether all the targets of a call are guaranteed to belong to the package. The identification of calls according to the invention can be performed at the time the package is sealed and signed or as a separate phase thereafter and allows for better compiler optimization.

Method for identifying calls in java packages whose targets are guaranteed to belong to the same package

A method and apparatus for minimizing spill code in regions of low register pressure determines the register pressure at various locations in the computer program. When a live range is selected for spilling, spill code is generated to relieve the register pressure in regions of high register pressure, while spill code is avoided in regions of low register pressure. In this manner a minimum amount of spill code is generated, enhancing both the compile time and the run time of the resultant instruction stream.

Register allocation method and apparatus for gernerating spill code as a

A method and apparatus for coloring an interference graph eliminates register copy instructions in an instruction stream by taking into consideration the colors of a node's direct or transitive partners when choosing a color for a node. By assigning a color to a node that is also the color of a direct or transitive partner, register copy instructions between the two partners may be eliminated. If more than one of the partners at any given level are colored, one of the colors may be selected over the others using an appropriate heuristic, such as a scheme that weights the colors appropriately.

Method and apparatus for using partner information to color nodes in an

A method and apparatus for coloring an interference graph yields a higher number of colored nodes by taking into consideration the colors of neighbors of a node's uncolored constrained neighbors. By assigning a color to a node that is also the color of a neighbor of an uncolored constrained neighbor, one color constraint is removed, increasing the probability of coloring the uncolored constrained neighbor. If more than one of the neighbors of the uncolored constrained neighbors are colored, one of the colors may be selected over the others using an appropriate heuristic.

Method and apparatus for improving colorability of constrained nodes in

A method and apparatus for truncating runaway lifetimes of program variables calculates liveness for each variable based on upwardly exposed uses. Reaching definitions are then calculated for at least the program variables that have runaway lifetimes. The liveness information is compared to the reaching definition information to determine whether a variable that is live upon entry to a basic block has a definition that reaches the end of each predecessor block, or has a use within the basic block. If the reaching definition for a variable reaches the beginning of the block and if there is a predecessor block for which there is no reaching definition, the variable has a runaway lifetime. The variable also has a runaway lifetime if there is a use of the variable in a block without a reaching definition for the variable at the beginning of the block. The runaway lifetime is truncated by inserting an instruction such as a pseudo-definition of the variable into the instruction stream at an appropriate place. Once runaway lifetimes are truncated using this method, subsequent stages of the compiler may calculate liveness by performing a single dataflow analysis which calculates lifetimes based on upwardly exposed uses.

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Haifa, Israel

Nava Arela Aizikowitz