Fast string moves

A method for a microprocessor to perform an Intel Architecture (IA-32) repeat move data from string to string (REP MOVS) macroinstruction, wherein the word length of the string is specified in the IA-32 architectural ECX register, the microprocessor including a memory for storing microinstruction sequences, the method comprising:

• in response to a macroinstruction that moves an immediate value into the IA-32 architectural ECX register, setting a flag and saving the immediate value;
• in response to a macroinstruction that modifies the IA-32 architectural ECX register in a manner other than moving an immediate value into the IA-32 architectural ECX register, clearing the flag;
• and
• in response to a REP MOVS macroinstruction:
• determining whether the flag is set or clear;
• transferring control to a first sequence of microinstructions for accomplishing the REP MOVS macroinstruction in the memory, if the flag is clear;
• and
• transferring control to a location within a second sequence of microinstructions for accomplishing the REP MOVS macroinstruction in the memory based on the saved immediate value, if the flag is set;
• wherein the first sequence of microinstructions includes a control transfer microinstruction that, when executed, conditionally transfers control to a microinstruction within the first sequence based on the word length stored in the IA-32 architectural ECX register;
• wherein the second sequence of microinstructions does not include any control transfer microinstructions that conditionally transfer control based on the word length stored in the IA-32 architectural ECX register.

A microprocessor for performing an Intel Architecture (IA-32) repeat move data from string to string (REP MOVS) macroinstruction, wherein the word length of the string is specified in the IA-32 architectural ECX register, the microprocessor comprising:

• a memory, configured to store a first sequence of microinstructions for accomplishing the REP MOVS macroinstruction that includes a control transfer microinstruction that, when executed, conditionally transfers control to a microinstruction within the first sequence based on the word length stored in the IA-32 architectural ECX register;
• and
• an instruction translator, coupled to said memory, configured to:
• in response to a macroinstruction that moves an immediate value into the IA-32 architectural ECX register, set a flag and save the immediate value;
• in response to a macroinstruction that modifies the IA-32 architectural ECX register in a manner other than moving an immediate value into the IA-32 architectural ECX register, clear the flag;
• and
• in response to a REP MOVS macroinstruction:
• transfer control to the first sequence of microinstructions in the memory, if the flag is clear;
• and
• generate a second sequence of microinstructions based on the saved immediate value, if the flag is set, wherein the second sequence of microinstructions accomplishes the REP MOVS macroinstruction, wherein the second sequence of microinstructions does not include any control transfer microinstructions that conditionally transfer control based on the word length stored in the IA-32 architectural ECX register.

A microprocessor for performing an Intel Architecture (IA-32) REP STOS, REP INS, REP OUTS, REP LODS, REP CMPS, or REP SCAS macroinstruction, wherein the word length of the string is specified in the IA-32 architectural ECX register, the microprocessor comprising:

• a memory, configured to store:
• a first sequence of microinstructions for accomplishing the REP STOS, REP INS, REP OUTS, REP LODS, REP CMPS, or REP SCAS macroinstruction that includes a control transfer microinstruction that, when executed, conditionally transfers control to a microinstruction within the first sequence based on the word length stored in the IA-32 architectural ECX register;
• and
• a second sequence of microinstructions for accomplishing the REP STOS, REP INS, REP OUTS, REP LODS, REP CMPS, or REP SCAS macroinstruction that does not include any control transfer microinstructions that conditionally transfer control based on the word length stored in the IA-32 architectural ECX register;
• and
• an instruction translator, coupled to said memory, configured to:
• in response to a macroinstruction that moves an immediate value into the IA-32 architectural ECX register, set a flag and save the immediate value;
• in response to a macroinstruction that modifies the IA-32 architectural ECX register in a manner other than moving an immediate value into the IA-32 architectural ECX register, clear the flag;
• and
• in response to a REP STOS, REP INS, REP OUTS, REP LODS, REP CMPS, or REP SCAS macroinstruction:
• transfer control to the first sequence of microinstructions in the memory, if the flag is clear;
• and
• transfer control to a location within the second sequence of microinstructions in the memory based on the saved immediate value, if the flag is set.

A computer program product for use with a computing device, the computer program product comprising:

• a computer usable storage medium, having computer readable program code embodied in said medium, for specifying a microprocessor for performing an Intel Architecture (IA-32) repeat move data from string to string (REP MOVS) macroinstruction, wherein the word length of the string is specified in the IA-32 architectural ECX register, the computer readable program code comprising:
• first program code for specifying a memory, configured to store:
• a first sequence of microinstructions for accomplishing the REP MOVS macroinstruction that includes a control transfer microinstruction that, when executed, conditionally transfers control to a microinstruction within the first sequence based on the word length stored in the IA-32 architectural ECX register;
• and
• a second sequence of microinstructions for accomplishing the REP MOVS macroinstruction that does not include any control transfer microinstructions that conditionally transfer control based on the word length stored in the IA-32 architectural ECX register;
• and
• second program code for specifying a an instruction translator, coupled to said memory, configured to:
• in response to a macroinstruction that moves an immediate value into the IA-32 architectural ECX register, set a flag and save the immediate value;
• in response to a macroinstruction that modifies the IA-32 architectural ECX register in a manner other than moving an immediate value into the IA-32 architectural ECX register, clear the flag;
• and
• in response to a REP MOVS macroinstruction:
• transfer control to the first sequence of microinstructions in the memory, if the flag is clear;
• and
• transfer control to a location within the second sequence of microinstructions in the memory based on the saved immediate value, if the flag is set.