4.12.1 VAX Compatibility Instructions
Format:
RxRa.wq!Memory format
Operation:
Ra ← intr_flag |
|
intr_flag ← 0 | !RC |
intr_flag ← 1 | !RS |
Exceptions: |
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None |
|
Instruction mnemonics: |
|
RC | Read and Clear |
RS | Read and Set |
Qualifiers: |
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None |
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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
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