dclst (Data Cache Line Store) instruction

Purpose

Stores a line of modified data in the data cache into main memory.

Syntax

Description

The dclst instruction adds the contents of general-purpose register (GPR) RA to the contents of GPR RB. It then stores the sum in RA as the effective address (EA) if RA is not 0 and the instruction does not cause a Data Storage interrupt.

If RA is 0, the effective address (EA) is the sum of the contents of GPR RB and 0.

Consider the following when using the dclst instruction:

• If the line containing the byte addressed by the EA is in the data cache and has been modified, the dclst instruction writes the line to main memory.
• If data address translation is enabled (that is, the Machine State Register (MSR) Data Relocate (DR) bit is 1) and the virtual address has no translation, a Data Storage interrupt occurs with bit 1 of the Data Storage Interrupt Segment Register set to 1.
• If data address translation is enabled (MSR DR bit is 1), the virtual address translates to an unusable real address, the line exists in the data cache, and a Machine Check interrupt occurs.
• If data address translation is disabled (MSR DR bit is 0) the address specifies an unusable real address, the line exists in the data cache, and a Machine Check interrupt occurs.
• If the EA specifies an I/O address, the instruction is treated as a no-op, but the effective address is placed into GPR RA.
• Address translation treats the dclst instruction as a load to the byte addressed, ignoring protection and data locking. If this instruction causes a Translation Look-Aside Buffer (TLB) miss, the reference bit is set.

The dclst instruction has one syntax form and does not effect the Fixed-Point Exception register. If the Record (Rc) bit is set to 1, Condition Register Field 0 is undefined.

Parameters

Examples

The following code stores the sum of the contents of GPR 4 and GPR 6 in GPR 6 as the effective address:

# Assume that GPR 4 contains 0x0000 3000.
# Assume that GPR 6 is the target register and that it
# contains 0x0000 0000.
dclst 6,4
# GPR 6 now contains 0x0000 3000.