Compaq ECQD2KCTE manual VAX Compatibility Instructions, Format

Models: ECQD2KCTE

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4.12.1 VAX Compatibility Instructions

Format:

RxRa.wq!Memory format

Operation:

Ra intr_flag

 

intr_flag 0

!RC

intr_flag 1

!RS

Exceptions:

 

None

 

Instruction mnemonics:

 

RC

Read and Clear

RS

Read and Set

Qualifiers:

 

None

 

Description:

The intr_flag is returned in Ra and then cleared to zero (RC) or set to one (RS).

These instructions may be used to determine whether the sequence of Alpha instructions between RS and RC (corresponding to a single VAX instruction) was executed without inter- ruption or exception.

Intr_flag is a per-processor state bit. The intr_flag is cleared if that processor encounters a CALL_PAL REI instruction.

It is UNPREDICTABLE whether a processor’s intr_flag is affected when that processor exe- cutes an LDx_L or STx_C instruction. A processor’s intr_flag is not affected when that processor executes a normal load or store instruction.

A processor’s intr_flag is not a ffected when that processor executes a taken branch.

Notes:

These instructions are intended only for use by the VAX-to-Alpha software translator; they should never be used by native code.

4–150Alpha Architecture Handbook

Page 206
Image 206
Compaq ECQD2KCTE manual VAX Compatibility Instructions, Format