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__int128 is not available on all platforms #634

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atsampson opened this issue Jan 28, 2023 · 3 comments · Fixed by #638
Closed

__int128 is not available on all platforms #634

atsampson opened this issue Jan 28, 2023 · 3 comments · Fixed by #638

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@atsampson
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Commit 1a0e13f ("Optimize csrand_uniform()") makes shadow unconditionally use GCC's __int128 extension type. However, this doesn't exist on all platforms - armv7, ia32 and m68k at least don't have it, so shadow now fails to build on those platforms:

csrand.c: In function 'csrand_uniform':
csrand.c:81:18: error: '__int128' is not supported on this target
@ikerexxe
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@alejandro-colomar can you take a look at this one? I think you already suggested a method to avoid this problem?

@alejandro-colomar
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Yup, I'll take it :)

alejandro-colomar added a commit to alejandro-colomar/shadow that referenced this issue Jan 30, 2023
@alejandro-colomar
Unoptimize the higher part of the domain of csrand_uniform()
81fd631 
__int128, which is needed for optimizing that part of the range, is not
always available.  We need the unoptimized version for portability
reasons.

Closes: <shadow-maint#634>
Fixes: 1a0e13f ("Optimize csrand_uniform()")
Reported-by: Adam Sampson <ats@offog.org>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
@alejandro-colomar alejandro-colomar mentioned this issue Jan 30, 2023
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ikerexxe pushed a commit that referenced this issue Jan 30, 2023
@alejandro-colomar @ikerexxe
Unoptimize the higher part of the domain of csrand_uniform()
2a61122 
__int128, which is needed for optimizing that part of the range, is not
always available.  We need the unoptimized version for portability
reasons.

Closes: <#634>
Fixes: 1a0e13f ("Optimize csrand_uniform()")
Reported-by: Adam Sampson <ats@offog.org>
Cc: Iker Pedrosa <ipedrosa@redhat.com>
Signed-off-by: Alejandro Colomar <alx@kernel.org>
@atsampson
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Great - that builds again on all my platforms. Thanks very much!

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Unoptimize the higher part of the domain of csrand_uniform() alejandro-colomar/shadow
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@atsampson @ikerexxe @alejandro-colomar