Apparatus and methods are disclosed for configuring, operating, and compiling code for, block-based processor architectures. In one example of the disclosed technology, a block-based processor includes processor cores configured to decode an instruction block header for a block-based processor instruction block including one or more fields and configure at least one of the cores to execute instructions in the instruction block according to a mode of operation specified by at least one of the fields, the modes including one or more of the following: core fusion operation, vector mode operation, memory dependence prediction operation, and/or deterministic order of execution.

The disclosed technology can be used for executing and committing instruction blocks of a block-based processor architecture out-of-order. In one example of the disclosed technology, an apparatus can include a plurality of block-based processor cores which can include a first group of cores and a second group of cores. The first group of cores can be configured to commit instruction blocks of the set of instruction blocks in a sequential program order. The second group of cores can be configured to commit instruction blocks of the set of instruction blocks out-of-order relative to the sequential program order.

Systems and methods are disclosed for fetching and decoding instructions in block-based processor architectures. In one example of the disclosed technology, a block-based processor core can be used for executing an instruction block. The instruction block can include an instruction header and one or more instructions. The block-based processor core can include header decode logic and fetch logic that are in communication with each other. The header decode logic can be configured to decode the instruction block header to determine starting positions of a plurality of sub-blocks within the instruction block. The fetch logic can be configured to initiate parallel fetch and decode operations for the plurality of sub-blocks.

Apparatus and methods are disclosed for nullifying memory store instructions and one or more registers identified in a target field of a nullification instruction. In some examples of the disclosed technology, an apparatus can include memory and one or more block-based processor cores configured to fetch and execute a plurality of instruction blocks. One of the cores can include a control unit configured, based at least in part on receiving a nullification instruction, to obtain an instruction identification for a memory access instruction of a plurality of memory access instructions and a register identification of at least one of a plurality of registers, based on a first and second target fields of the nullification instruction. The at least one register and the memory access instruction associated with the instruction identification are nullified. Based on the nullified memory access instruction, a subsequent memory access instruction is executed.

Technology related to prefetching instruction blocks is disclosed. In one example of the disclosed technology, a processor comprises a block-based processor core for executing a program comprising a plurality of instruction blocks. The block-based processor core can include prefetch logic and a local buffer. The prefetch logic can be configured to receive a reference to a predicted instruction block and to determine a mapping of the predicted instruction block to one or more lines. The local buffer can be configured to selectively store portions of the predicted instruction block and to provide the stored portions of the predicted instruction block when control of the program passes along a predicted execution path to the predicted instruction block.

Apparatus and methods are disclosed for controlling execution of register access instructions in a block-based processor architecture using a hardware structure that indicates a relative ordering of register access instruction in an instruction block. In one example of the disclosed technology, a method of operating a processor includes selecting a register access instruction of the plurality of instructions to execute based at least in part on dependencies encoded within a previous block of instructions and on stored data indicating which of the register write instructions have executed for the previous block, and executing the selected instruction. In some examples, one or more of a write mask, a read mask, a register write vector register, or a counter are used to determine register read/write dependences. Based on the encoded dependencies and the masked write vector, the next instruction block can issue when its register dependencies are available.

Technology related to prefetching data associated with predicated stores of programs in block-based processor architectures is disclosed. In one example of the disclosed technology, a processor includes a block-based processor core for executing an instruction block comprising a plurality of instructions. The block-based processor core includes decode logic and prefetch logic. The decode logic is configured to detect a predicated store instruction of the instruction block. The prefetch logic is configured to calculate a target address of the predicated store instruction and initiate a memory operation associated with the calculated target address before a predicate of the predicated store instruction is calculated.

Technology related to prefetching data associated with predicated loads of programs in block-based processor architectures is disclosed. In one example of the disclosed technology, a processor includes a block-based processor core for executing an instruction block comprising a plurality of instructions. The block-based processor core includes decode logic and prefetch logic. The decode logic is configured to detect a predicated load instruction of the instruction block. The prefetch logic is configured to calculate a target address of the predicated load instruction and issue a prefetch request to a memory hierarchy of the processor for data at the calculated target address.

Apparatus and methods are disclosed for controlling instruction flow in block-based processor architectures. In one example of the disclosed technology, an instruction block address register stores an index address to a memory storing a plurality of instructions for an instruction block, the indexed address being inaccessible when the processor is in one or more unprivileged operational modes, one or more execution units configured to execute instructions for the instruction block, and a control unit configured to fetch and decode two or more of the plurality of instructions from the memory based on the indexed address.

Apparatus and methods are disclosed for initiating instruction block execution using a register access instruction (e.g., a register Read instruction). In some examples of the disclosed technology, a block-based computing system can include a plurality of processor cores configured to execute at least one instruction block. The at least one instruction block encodes a data-flow instruction set architecture (ISA). The ISA includes a first plurality of instructions and a second plurality of instructions. One or more of the first plurality of instructions specify at least a first target instruction without specifying a data source operand. One or more of the second plurality of instructions specify at least a second target instruction and a data source operand that specifies a register.