International Business Machines Corporation

Ram Rangan

Mark William Stephenson

Lixin Zhang

William Evan Speight

A technique for handling predicated code in an out-of-order processor includes detecting a predicate defining instruction associated with a predicated code region. Renaming of predicated instructions, within the predicated code region, is then stalled until a predicate of the predicate defining instruction is resolved.

Techniques for predicated execution in an out-of-order processor

A predication technique for out-of-order instruction processing provides efficient out-of-order execution with low hardware overhead. A special op-code demarks unified regions of program code that contain predicated instructions that depend on the resolution of a condition. Field(s) or operand(s) associated with the special op-code indicate the number of instructions that follow the op-code and also contain an indication of the association of each instruction with its corresponding conditional path. Each conditional register write in a region has a corresponding register write for each conditional path, with additional register writes inserted by the compiler if symmetry is not already present, forming a coupled set of register writes. Therefore, a unified instruction stream can be decoded and dispatched with the register writes all associated with the same re-name resource, and the conditional register write is resolved by executing the particular instruction specified by the resolved condition.

Predication supporting code generation by indicating path associations of symmetrically placed write instructions

A method, computer system, and computer program product for using one or more hardware interrupts to drive dynamic binary code recompilation. The execution of a plurality of instructions is monitored to detect a problematic instruction. In response to detecting the problematic instruction, a hardware interrupt is thrown to a dynamic interrupt handler. A determination is made whether a threshold for dynamic binary code recompilation is satisfied. If the threshold for dynamic code recompilation is satisfied, the dynamic interrupt handler optimizes at least one of the plurality of instructions.

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Ram Rangan