ASM and JNI

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Roedy Green - 29 May 2004 10:40 GMT

When you write your JNI in assembler for Windows, and you want to
return a long, which register pair does it go in, and which is the
high order?

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Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

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Roedy Green - 29 May 2004 11:00 GMT

>When you write your JNI in assembler for Windows, and you want to
>return a long, which register pair does it go in, and which is the
>high order?

edx:eax where edx is the high order. I finally found the /FA switch
in the projects settings that generates *.ASM files which lets you
figure out the register conventions by looking an ASM code generated
from C and C++.

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Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

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glen herrmannsfeldt - 02 Jun 2004 23:57 GMT

> When you write your JNI in assembler for Windows, and you want to
> return a long, which register pair does it go in, and which is the
> high order?

All x86 code that I know of use EDX:EAX with EDX high.

At least one that I know of, the RDTSC instruction,
returns it that way. My favorite JNI has the executable
assembly code:

rdtsc
ret

with a few more instruction to tell the assembler what
to do with it, but that aren't executable.

-- glen

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striker - 04 Jun 2004 04:44 GMT

Under win32 you dont need to register pair. EAX is sufficient.

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Roedy Green - 04 Jun 2004 05:59 GMT

>Under win32 you dont need to register pair. EAX is sufficient.

for returning a jlong 64 bits you need two registers. edx:eax.

See the source code at http://mindprod.com/products.html#PENTIUM

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Canadian Mind Products, Roedy Green.
Coaching, problem solving, economical contract programming.
See http://mindprod.com/jgloss/jgloss.html for The Java Glossary.

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ASM and JNI

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