Reservation station with multiple entry types
A reservation station that includes a storage circuit with multiple full and partial entries is disclosed. A given store-data entry of the multiple partial entries may store less data than a given full entry of the multiple full entries. A control circuit may receive a load/store operation and, in response to a determination that the load/store operation includes only a single source, store the load/store operation in a particular partial entry of the multiple partial entries.
1 . An apparatus, comprising:
a primary storage circuit including a plurality of full entries and a plurality of partial entries, wherein a given full entry of the plurality of full entries is configured to store a first amount of data, and wherein a given partial entry of the plurality of partial entries is configured to store a second amount of data less than the first amount of data;
a secondary storage circuit, and
a control circuit configured to:
receive a first load/store operation; and
store the first load/store operation in a particular partial entry of the plurality of partial entries in response to a determination that the first load/store operation includes only a single source; and
transfer a particular store operation from the primary storage circuit to the secondary storage circuit in response to a determination that the particular store operation is delinquent.
2 . The apparatus of claim 1 , wherein the control circuit is further configured to:
receive a second load/store operation; and
store the second load/store operation in a particular full entry of the plurality of full entries in response to a determination that the second load/store operation includes more than one source.
3 . The apparatus of claim 1 , wherein to store the first load/store operation, the control circuit is further configured to:
check for an available credit; and
in response to a determination that no credits are available, store the first load/store operation in a particular full entry of the plurality of full entries.
4 . The apparatus of claim 1 , wherein the primary storage circuit further includes a plurality of load-partial entries, wherein a given load-partial entry of the plurality of load-partial entries is configured to store a third amount of data less than the second amount of data, and wherein the control circuit is further configured to:
receive a second load/store operation; and
in response to a determination that the second load/store operation is a single-source load operation, store the second load/store operation in a particular load-partial entry of the plurality of load-partial entries.
5 . The apparatus of claim 4 , wherein the control circuit is further configured to:
link a different full entry of the plurality of full entries to a different load-partial entry of the plurality of load-partial entries to form a pair entry; and
store a third load/store operation in a portion of the pair entry in response to a determination that the third load/store operation has multiple sources and that there are no free full entries in the plurality of full entries.
6 . The apparatus of claim 1 , wherein to transfer the particular store operation, the control circuit is further configured to select an oldest delinquent entry of a plurality of delinquent entries.
7 . A method, comprising:
receiving, by a reservation station, a first load/store operation, wherein the reservation station includes a primary storage circuit including a plurality of full entries, and a plurality of partial entries, wherein a given full entry of the plurality of full entries is configured to store a first amount of data, and wherein a given partial entry of the plurality of partial entries is configured to store a second amount of data less than the first amount of data, and wherein the reservation station further includes a secondary storage circuit;
checking, by the reservation station, first characteristics of the first load/store operation;
storing, by the reservation station, the first load/store operation in a particular partial entry of the plurality of partial entries in response to determining that the first load/store operation includes only a single source; and
transferring a particular store operation from a particular full entry of the plurality of full entries to the secondary storage circuit in response to determining that a store address associated with the particular store operation has been available for use for a threshold number of cycles without store data associated with the particular store operation being available for use.
8 . The method of claim 7 , further comprising:
receiving, by the reservation station, a second load/store operation;
checking, by the reservation station, second characteristics of the second load/store operation; and
storing the second load/store operation in a particular full entry of the plurality of full entries in response to determining that the second load/store operation includes more than one source.
9 . The method of claim 7 , further comprising:
receiving, by the reservation station, a second load/store operation that includes a single source;
checking, by the reservation station, for an available credit associated with the plurality of partial entries; and
storing, by the reservation station in response to determining that no credits are available, the second load/store operation in a particular full entry of the plurality of full entries.
10 . The method of claim 7 , further comprising:
requesting, by the reservation station, a credit associated with the plurality of partial entries;
storing, by the reservation station in response to receiving the credit, the first load/store operation in the particular partial entry; and
releasing, by the reservation station in response to issuing the first load/store operation, the credit.
11 . The method of claim 7 , wherein the primary storage circuit further includes a plurality of load-partial entries, wherein a given load-partial entry of the plurality of load-partial entries is configured to store a third amount of data less than the second amount of data, and further comprising:
receiving, by the reservation station, a second load/store operation; and
storing, by the reservation station in response to a determination that the second load/store operation is a single-source load operation, the second load/store operation in a particular load-partial entry of the plurality of load-partial entries.
12 . The method of claim 11 , further comprising:
linking, by the reservation station, a different full entry of the plurality of full entries to a different load-partial entry of the plurality of load-partial entries to form a pair entry; and
storing, by the reservation station, a third load/store operation in a portion of the pair entry in response to determining that the third load/store operation has multiple sources and that there is no free full entry in the plurality of full entries.
13 . The method of claim 7 , wherein transferring the particular store operation includes selecting an oldest delinquent entry of a plurality of delinquent entries.
14 . A processor circuit, comprising:
a plurality of execution units; and
a reservation station that includes a primary storage circuit that includes a plurality of full entries and a plurality of partial entries, wherein a given full entry of the plurality of full entries is configured to store a first amount of data, wherein a given partial entry of the plurality of partial entries is configured to store a second amount of data less than the first amount of data, wherein the reservation station further includes a secondary storage circuit, and wherein the reservation station is configured to:
receive a first load/store operation;
check first characteristics of the first load/store operation;
store the first load/store operation in a particular partial entry of the plurality of partial entries in response to a determination that the first load/store operation includes only a single source; and
transfer a particular store operation from the primary storage circuit to the secondary storage circuit in response to a determination that a store address associated with the particular store operation has been available for use for a threshold number of cycles without store data associated with the particular store operation being available for use.
15 . The processor circuit of claim 14 , wherein the reservation station is further configured to:
receive a second load/store operation;
check second characteristics of the second load/store operation; and
store the second load/store operation in a particular full entry of the plurality of full entries in response to a determination that the second load/store operation includes more than one source.
16 . The processor circuit of claim 14 , wherein the reservation station is further configured to:
receive a second load/store operation that includes a single source;
check for an available credit associated with the plurality of partial entries; and
store the second load/store operation in a particular full entry of the plurality of full entries in response to a determination that no credits associated with the plurality of partial entries are available.
17 . The processor circuit of claim 14 , wherein the reservation station is further configured to:
request a credit associated with the plurality of partial entries;
store the first load/store operation in the particular partial entry in response to receiving the credit; and
release the credit in response to issuing the first load/store operation to a given one of the plurality of execution units.
18 . The processor circuit of claim 14 , wherein the primary storage circuit further includes a plurality of load-partial entries, wherein a given load-partial entry of the plurality of load-partial entries is configured to store a third amount of data less than the second amount of data, and wherein the reservation station is further configured to:
receive a second load/store operation; and
store the second load/store operation in a particular load partial entry of the plurality of load-partial entries in response to a determination that the second load/store operation is a single-source load operation.
19 . The processor circuit of claim 18 , wherein the reservation station is further configured to:
link a different full entry of the plurality of full entries to a different load-partial entry of the plurality of load-partial entries to form a pair entry; and
store a third load/store operation in a portion of the pair entry in response to a determination that the third load/store operation has multiple sources and that there is no free full entry in the plurality of full entries.
20 . The processor circuit of claim 14 , wherein to transfer the particular store operation, the reservation station is further configured to select an oldest store operation from a plurality of store operations having corresponding store addresses that have been available for the threshold number of cycles.