A tangible medium storing computer readable instructions for use at the linker stage and adapted to improve the performance of an executable for a specific target computer system comprising at least one processor, software storage and read/write memory including caches, buffers and accelerators, the computer readable instructions comprising: instructions for receiving one or more of object files and library files containing unresolved object file symbols and for analysing instruction sequences and data structures therein used in generation of the executable; and instructions for generating an executable, characterised by the computer readable instructions further comprising: instructions for determining interactions of said object files and library files, the processor pipeline and the read/write memory of the target computer system with respect to one or more of: relationships between said instruction sequences; relationships between said data structures; and relationships between said instruction sequences and said data structures; instructions for re-sequencing one or more of: (i) at least one of said instruction sequences, and (ii) at least one of said data structures, to generate re-sequenced versions each re-sequenced version having a different set of at least one re-sequenced instruction sequence and/or data structure; instructions for determining statically for each re-sequenced version an Average Case Execution Time (ACET) with respect to one or more processors and one or more memories of the target computer system; instructions for selecting one of the re-sequenced versions based on its ACET; and instructions for resolving object file symbols to addresses after selection of one or more re-sequenced versions, wherein a target specific optimized executable is generated using one or more selected re-sequenced versions. instructions for receiving one or more of object files and library files containing unresolved object file symbols and for analysing instruction sequences and data structures therein used in generation of the executable; and instructions for generating an executable, characterised by the computer readable instructions further comprising: instructions for determining interactions of said object files and library files, the processor pipeline and the read/write memory of the target computer system with respect to one or more of: relationships between said instruction sequences; relationships between said data structures; and relationships between said instruction sequences and said data structures; instructions for re-sequencing one or more of: (i) at least one of said instruction sequences, and (ii) at least one of said data structures, to generate re-sequenced versions each re-sequenced version having a different set of at least one re-sequenced instruction sequence and/or data structure; instructions for determining statically for each re-sequenced version an Average Case Execution Time (ACET) with respect to one or more processors and one or more memories of the target computer system; instructions for selecting one of the re-sequenced versions based on its ACET; and instructions for resolving object file symbols to addresses after selection of one or more re-sequenced versions, instructions for determining interactions of said object files and library files, the processor pipeline and the read/write memory of the target computer system with respect to one or more of: relationships between said instruction sequences; relationships between said data structures; and relationships between said instruction sequences and said data structures; instructions for re-sequencing one or more of: (i) at least one of said instruction sequences, and (ii) at least one of said data structures, to generate re-sequenced versions each re-sequenced version having a different set of at least one re-sequenced instruction sequence and/or data structure; (i) at least one of said instruction sequences, and (ii) at least one of said data structures, instructions for determining statically for each re-sequenced version an Average Case Execution Time (ACET) with respect to one or more processors and one or more memories of the target computer system; instructions for selecting one of the re-sequenced versions based on its ACET; and instructions for resolving object file symbols to addresses after selection of one or more re-sequenced versions, wherein a target specific optimized executable is generated using one or more selected re-sequenced versions.