Abstract: A dynamic code translator with isoblocking uses a return trampoline having branch instructions conditioned on different isostates to optimize return address translation, by allowing the hardware to predict that the address of a future return will be the address of trampoline. An IP relative call is inserted into translated code to write the trampoline address to a target link register and a target return address stack used by the native machine to predict return addresses. If a computed subject return address matches a subject return address register value, the current isostate of the isoblock is written to an isostate register. The isostate value in the isostate register is then used to select the branch instruction in the trampoline for the true subject return address. Sufficient code area in the trampoline instruction set can be reserved for a number of compare/branch pairs which is equal to the number of available isostates.

Abstract: A dynamic code translator with isoblocking uses a return trampoline having branch instructions conditioned on different isostates to optimize return address translation, by allowing the hardware to predict that the address of a future return will be the address of trampoline. An IP relative call is inserted into translated code to write the trampoline address to a target link register and a target return address stack used by the native machine to predict return addresses. If a computed subject return address matches a subject return address register value, the current isostate of the isoblock is written to an isostate register. The isostate value in the isostate register is then used to select the branch instruction in the trampoline for the true subject return address. Sufficient code area in the trampoline instruction set can be reserved for a number of compare/branch pairs which is equal to the number of available isostates.

Abstract: A dynamic code translator with isoblocking uses a return trampoline having branch instructions conditioned on different isostates to optimize return address translation, by allowing the hardware to predict that the address of a future return will be the address of trampoline. An IP relative call is inserted into translated code to write the trampoline address to a target link register and a target return address stack used by the native machine to predict return addresses. If a computed subject return address matches a subject return address register value, the current isostate of the isoblock is written to an isostate register. The isostate value in the isostate register is then used to select the branch instruction in the trampoline for the true subject return address. Sufficient code area in the trampoline instruction set can be reserved for a number of compare/branch pairs which is equal to the number of available isostates.

Abstract: During program code conversion, such as in a dynamic binary translator, automatic code generation provides target code 21 executable by a target processor 13. Multiple instruction ports 610 disperse a group of instructions to functional units 620 of the processor 13. Disclosed is a mechanism of preparing an instruction group 606 using a plurality of pools 700 having a hierarchical structure 711-715. Each pool represents a different overlapping subset of the issue ports 610. Placing an instruction 600 into a particular pool 700 also reduces vacancies in any one or more subsidiary pools in the hierarchy. In a preferred embodiment, a counter value 702 is associated with each pool 700 to track vacancies. A valid instruction group 606 is formed by picking the placed instructions 600 from the pools 700. The instruction groups are generated accurately and automatically. Decoding errors and stalls are minimized or completely avoided.