Filter
Top Products
4–150 Alpha Architecture Handbook
4.12.1 VAX Compatibility Instructions
Format:
Operation:
Ra ← intr_flag
intr_flag ← 0 !RC
intr_flag ← 1 !RS
Exceptions:
Instruction mnemonics:
Qualifiers:
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 affected 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.
Rx Ra.wq
!Memory format
None
RC Read and Clear
RS Read and Set
None