Partial connection of iterations during loop unrolling

A computer program product, comprising one or more computer readable hardware storage devices having computer readable program instructions stored therein, said program instructions executable by one or more processors of a computer system to implement a method for partial connection of iterations during loop unrolling during compilation of a program by a compiler, said method comprising:

• selectively connecting, by the one or more processors during the compilation, unrolled loop iterations of a loop in the program, wherein said selectively connecting unrolled loop iterations comprises redirecting, to the head of the loop, edges of a control flow for the program that are classed as undesirable from one iteration of the loop to a next iteration of the loop, and wherein the head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow for the program;
• removing, by the one or more processors during the compilation, merges on a path of hot code in the loop to increase a scope for optimization of the program;
• and
• extending, by the one or more processors during the compilation, a sequence of blocks on the path of hot code, unpolluted by a control flow of a path of cold code, wherein information computed by an optimizer in or invoked by the compiler about the hot code in a first iteration of the loop is used to further optimize a second iteration of the loop, and wherein the loop is further unrolled.

A computer system, comprising one or more processors, one or more memories, and one or more computer readable hardware storage devices, said one or more hardware storage device containing program instructions executable by the one or more processors via the one or more memories to implement a method for partial connection of iterations during loop unrolling during compilation of a program by a compiler, said method comprising:

• selectively connecting, by the one or more processors during the compilation, unrolled loop iterations of a loop in the program, wherein said selectively connecting unrolled loop iterations comprises redirecting, to the head of the loop, edges of a control flow for the program that are classed as undesirable from one iteration of the loop to a next iteration of the loop, and wherein the head of the loop and a start of a replicated loop body of the loop are equivalent points of the control flow for the program;
• removing, by the one or more processors during the compilation, merges on a path of hot code in the loop to increase a scope for optimization of the program;
• and
• extending, by the one or more processors during the compilation, a sequence of blocks on the path of hot code, unpolluted by a control flow of a path of cold code, wherein information computed by an optimizer in or invoked by the compiler about the hot code in a first iteration of the loop is used to further optimize a second iteration of the loop, and wherein the loop is further unrolled.