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ATI R700 Technology

4-10 Scalar Operands

• The previous vector (PV) or scalar (PS) result.

• A literal constant (two constants are present if any operand uses a Z or W

constant).

• A floating-point inline constant (0.0, 0.5, 1.0).

• An integer inline constant (-1, 0, 1).

If the SRC*_SEL field specifies a GPR or constant-register address, then the

relative index specified by the INDEX_MODE field is added to the address if the

SRC*_REL bit is set.

The definitions of the selects for PV, PS, literal constant, and the special inline

constant values are given in the microcode specification. Also, the following

constant values are defined to assist in encoding and decoding the SRC*_SEL

field:

• ALU_SRC_GPR_BASE = 0 — Base value for GPR selects.

• ALU_SRC_KCACHE0_BASE = 128 — Base value for kcache bank 0 selects.

• ALU_SRC_KCACHE1_BASE = 144 — Base value for kcache bank 1 selects.

• ALU_SRC_CFILE_BASE = 256 — Base value for constant-register address

selects.

The SRC*_ELEM field specifies from which vector element of the source address

to read. It is ignored when PS is specified. If a literal constant is selected, and

SRC*_ELEM specifies the Z or W element; then, both slots of the literal constant

must be specified at the end of the instruction group.

4.7.2 Input Modifiers

Each input operand can be modified. The modifiers available are negate,

absolute value, and absolute-then-negate; they are specified using the SRC*_NEG

and SRC*_ABS fields. The modifiers are meaningful only for floating-point inputs.

Integer inputs must leave these fields cleared (zero), which is the pass-through

value. If the SRC*_NEG and SRC*_ABS bits are set, the absolute value is performed

first. Instructions with three source operands have only the negation modifier,

SRC*_NEG; absolute value, if desired, must be performed by a separate instruction

with two source operands.

4.7.3 Data Flow

A simplified data flow for the ALU operands is given in Figure 4.3. The data flow

is discussed in more detail in the following sections.

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Boxis R700 Manuel d'utilisateur Page 68