US 7,254,693 B2 · Selectively prohibiting speculative execution of conditional branch type based on instruction bit

Abstract

A method, apparatus, and computer program product are disclosed for selectively prohibiting speculative conditional branch execution. A particular type of conditional branch instruction is selected. An indication is stored within each instruction that is the particular type of conditional branch instruction. A processor then fetches a first instruction from code that is to be executed. A determination is made regarding whether the first instruction includes the indication. In response to determining that the instruction includes the indication: speculative execution of the first instruction is prohibited, an actual location to which the first instruction will branch is resolved, and execution of the code is branched to the actual location. In response to determining that the instruction does not include the indication, the first instruction is speculatively executed.

Claims17

Dependent claims

A method in a data processing system for selectively prohibiting speculative conditional branch execution, said method comprising:

selecting a particular type of conditional branch instruction;
including an indication within each instruction that is said particular type of conditional branch instruction, said indication comprising setting of a specified bit within an opcode of each instruction that is said particular type of conditional branch instruction;
fetching, by a processor, a first instruction to be executed;
determining whether said first instruction includes said indication;
in response to determining that said first instruction includes said indication:
prohibiting speculative execution of said first instruction;
resolving an actual location to which said first instruction will branch;
and
branching to said actual location;
and
in response to determining that said first instruction does not include said indication:
speculatively executing said first instruction.

9 more elements

An apparatus in a data processing system for selectively prohibiting speculative conditional branch execution, said apparatus comprising:

a particular type of conditional branch instruction being selected;
an indication included within each instruction that is said particular type of conditional branch instruction, said indication comprising setting of a specified bit within an opcode of each instruction that is said particular type of conditional branch instruction;
a processor for fetching a first instruction to be executed;
said processor determining whether said first instruction includes said indication;
in response to determining that said first instruction includes said indication:
said processor prohibiting speculative execution of said first instruction;
said processor resolving an actual location to which said first instruction will branch;
and
said processor branching to said actual location;
and
in response to determining that said first instruction does not include said indication,
said processor speculatively executing said first instruction.

9 more elements

Dependencies are inferred from the claim text.

Selectively prohibiting speculative execution of conditional branch type based on instruction bit

Life of this patent

Selectively prohibiting speculative execution of conditional branch type based on instruction bit

Life of this patent

Abstract

Claims17