VAX MACRO and Instruction Set Reference Manual

vector-vector: opcode cntrl.rw

vector-scalar: opcode cntrl.rw,src.rq

Opcodes

EEFD VVMERGE Vector Vector Merge

EFFD VSMERGE Vector Scalar Merge

None.

Description

The scalar src or vector operand Va is merged, elementwise, with vector register Vb and the resulting vector is written to vector register Vc. The length of the vector operation is specified by the Vector Length Register (VLR).
For each vector element, i, if the corresponding Vector Mask Register bit (VMR<i>) matches cntrl<MTF>, src or Va[i] is written to the destination vector element Vc[i]. If VMR<i> does not match cntrl<MTF>, Vb[i] is written to the destination vector element.

IOTA

Generate Compressed Iota Vector

Format

IOTA [/0|1] stride, Vc

Architecture

opcode cntrl.rw, stride.rl

Opcodes

EDFD IOTA Generate Compressed Iota Vector

None.

Description

IOTA constructs a vector of offsets for use by the vector gather/scatter instructions VGATH and VSCAT.
IOTA first generates an iota vector of length VLR using the stride operand. An iota vector is a vector whose first element is zero and whose subsequent elements are spaced by the stride increment. The stride can be positive, negative, or zero. For example:
0*stride, 1*stride, 2*stride, 3*stride, ..., {VLR-1}*stride
The iota vector is then compressed using the contents of the Vector Mask Register (VMR). Elements of the iota vector for which the corresponding Vector Mask Register bit matches cntrl<MTF> are written in contiguous elements of the destination vector register Vc. Only bits <31:0> of each iota and destination vector element participate in the operation. Bits <63:32> of the destination vector elements are UNPREDICTABLE.
The number of elements written to Vc is returned in the Vector Count Register (VCR). The values of elements in the destination vector register between the new value of VCR and the vector length are UNPREDICTABLE.

Note
If a large value is specified for the stride.rl operand, there is a chance for integer overflow during calculation of the "tmp <- tmp + stride" step. In this case, the overflow is ignored. For example:

tmp <- tmp + stride Value of tmp before above step: FFFFFF00 Value of Stride: FFFFFF00 Value of tmp + stride: 1 FFFFFE00 Since the overflow is ignored, the new value of tmp is FFFFFE00.

10.15 Miscellaneous Instructions

This section describes VAX vector architecture miscellaneous instructions.

MFVP

Move from Vector Processor

Format

{MFVCR|MFVLR|MFVMRLO|MFVMRHI|SYNCH|MSYNCH} dst

Architecture

opcode regnum.rw, dst.wl

Opcodes

31FD MFVP Move from Vector Processor

None.

None.

MFVP instructions that specify reserved values of the regnum operand produce UNPREDICTABLE results.

Description

This instruction can be used to read the Vector Count, Length, and Mask Registers, and to synchronize a scalar processor with its associated vector processor.
When the scalar processor issues an MFVP instruction to the vector processor, the scalar processor waits for the MFVP result to be written before processing other instructions.
MFVP from VCR or VLR does not read that register until all previous write operations to the register are completed. MFVP from VMR<31:0> or VMR<63:32> does not read that longword of VMR until all previous write operations to the same longword of VMR are completed; however, this is not true for previous write operations to the other longword.
SYNC allows software to ensure that the unreported exceptions of all previously issued vector instructions (including vector memory instructions in asynchronous memory management mode) are detected and reported to the scalar processor before the scalar processor proceeds with further instructions. For more details about SYNC and its exception reporting nature refer to Section 10.7.1, Scalar/Vector Instruction Synchronization.
MSYNC allows software to ensure that all previously issued memory instructions of the scalar/vector processor pair are complete before the scalar processor proceeds with further instructions. For more details about MSYNC and its exception reporting nature, refer to Section 10.7.2, Memory Instruction Synchronization.
The value of the vector control register (VCR, VLR, VMR<31:0>, VMR<63:32>) delivered by an MFVP depends upon the value of certain vector register elements and vector control register bits. Unreported exceptions that occur in the production of these elements and control register bits are reported by the vector processor prior to the completion of the MFVP from the vector control register.
In addition, there are vector register elements and vector control register bits that the value of a vector control register delivered by an MFVP does not depend upon. It is UNPREDICTABLE whether unreported exceptions that occur in the production of these elements and control register bits are reported by the vector processor prior to the completion of the MFVP from the vector control register. Software must not rely upon the reporting of these exceptions prior to the completion of the MFVP for the correctness of program results.
Section 10.5.3.3, Dependencies Among Vector Results, gives the necessary rules to determine what vector control register elements and vector control register bits the value of a vector control register delivered by an MFVP depends upon. Examples of MFVP exception reporting using these rules are found in Section 10.6.5.
When a vector arithmetic exception or memory management exception (in asynchronous memory management mode) is reported prior to the completion of an MFVP, the following occur:

The operation of the MFVP does not complete.
No longword result is written to the scalar destination of the MFVP by the scalar processor.
The MFVP itself (rather than the next vector instruction) takes either a vector processor disabled fault or a memory management fault.

After the appropriate fault has been serviced, the MFVP may be returned to through an REI. If both exception conditions are encountered by an MFVP, then the MFVP itself takes a vector processor disabled fault. In this case, after the vector processor disabled fault has been serviced, returning to the MFVP instruction will cause the asynchronous memory management exception to be reported.

MTVP

Move to Vector Processor

Format

{MTVCR|MTVLR|MTVMRLO|MTVMRHI} src

Architecture

opcode regnum.rw, src.rl

Opcodes

A9FD MTVP Move to Vector Processor

None.

None.

Move to Vector Processor instructions that specify reserved values of the regnum operand produce UNPREDICTABLE results.

Description

This instruction can be used to write the Vector Count, Length, and Mask Registers.
The new value of VCR, VLR, or VMR does not affect any prior instructions. The new value remains in effect for all subsequent vector instructions executed until a new value is loaded.

VSYNC

Synchronize Vector Memory Access

Format

VSYNCH

Architecture

opcode regnum.rw

Opcodes

A8FD VSYNC Synchronize Vector Memory Access

None.