[Qemu-devel] ARM CPSR and conditional instructions

[Qemu-devel] ARM CPSR and conditional instructions

[Torbjörn Andersson]

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Hello qemu developers!

I´m using QEMU for some ARM debugging and I have som questions regardning
the CPSR register. I get the feeling that the CPSR condition code bits,
representing the results from the ALU, are not maintained at all points. Is
the JIT in QEMU tailored in any way towards GCC output? (Resulting in issues
with the output of other compilers that make use of the conditional
execution of instructions etc.)


What I want to do is to try to verify QEMU maintains the CPSR register and
if not fix it. However, it is not trivial identify where the updates should
be placed. The relationship between translate.c and op.c is not trival I
must say :)



I would be happy I anyone here could give me some pointers on how the
updates of the CPSR register is done today and what the strategy is. I guess
there are plenty of performance ideas here as in the rest of qemu.

Does anyone have any reflection on this topic or can anyone give me some
pointers?

Torbjörn


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[Qemu-devel] ARM CPSR and conditional instructions

[Torbjörn Andersson]

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Hello qemu developers!

I´m using QEMU for some ARM debugging and I have som questions regardning
the CPSR register. I get the feeling that the CPSR condition code bits,
representing the results from the ALU, are not maintained at all points. Is
the JIT in QEMU tailored in any way towards GCC output? (Resulting in issues
with the output of other compilers that make use of the conditional
execution of instructions etc.)


What I want to do is to try to verify QEMU maintains the CPSR register and
if not fix it. However, it is not trivial identify where the updates should
be placed. The relationship between translate.c and op.c is not trival I
must say :)

I would be happy I anyone here could give me some pointers on how the
updates of the CPSR register is done today and what the strategy is. I guess
there are plenty of performance ideas here as in the rest of qemu.

Does anyone have any reflection on this topic or can anyone give me some
pointers?

Torbjörn

 


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