GR740-UM-DS, Nov 2017, Version 1.7
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GR740
After the trap is taken the
qne
bit of the FSR is set and remains set until the FQ is emptied. The
STDFQ instruction reads a double-word from the floating-point deferred queue, the first word is the
address of the instruction and the second word is the instruction code. All instructions in the FQ are
FPop type instructions. The first access to the FQ gives a double-word with the trap-inducing instruc-
tion, following double-words contain pending floating-point instructions. Supervisor software should
emulate FPops from the FQ in the same order as they were read from the FQ.
Note that instructions in the FQ may not appear in the same order as the program order since GRFPU
executes floating-point instructions out-of-order. A floating-point trap is never deferred past an
instruction specifying source registers, destination registers or condition codes that could be modified
by the trap-inducing instruction. Execution or emulation of instructions in the FQ by the supervisor
software gives therefore the same FPU state as if the instructions were executed in the program order.