llvm dev - Jul 2015 - [LLVMdev] [Clang] Reasons for lack of -fsingle-precision-constant support? Alternatives?

Thanks for the response.  If we add the support would you accept the
patch?  Seems like a pretty straightforward flag since it maps directly to
NumericLiteralParser::NumericLiteralParser within LiteralSupport.cpp.  I
understand the maintenance concern with flags that affect multiple points
in code though.

Still trying to get the bottom of why we're crashing with double floating
point literal.  It seems the fpu in question (fpv4-sp-d16) only supports 32
bit operations so this is somehow getting passed to a software wrapper and
crashing there.  But to be fair this was crashing in gcc too which is why
we added the -fsingle-precision-constant flag since we didn't care about
the precision of the constants and we're using floats everywhere anyway for
performance.
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> On Jul 15, 2015, at 09:08 , ed at modk.it wrote:
> 
> Thanks for the response.  If we add the support would you accept the patch?
Seems like a pretty straightforward flag since it maps directly to
NumericLiteralParser::NumericLiteralParser within LiteralSupport.cpp.  I
understand the maintenance concern with flags that affect multiple points in
code though.
> 
> Still trying to get the bottom of why we're crashing with double
floating point literal.  It seems the fpu in question (fpv4-sp-d16) only
supports 32 bit operations so this is somehow getting passed to a software
wrapper and crashing there.  But to be fair this was crashing in gcc too which
is why we added the -fsingle-precision-constant flag since we didn't care
about the precision of the constants and we're using floats everywhere
anyway for performance.
Shouldn't the code generator know to make the constants 32-bit if that's
all the target supports? Or does it emulate 64-bit in software?

-- 
Rick Mann
rmann at latencyzero.com

>
> > Still trying to get the bottom of why we're crashing with double
> floating point literal.  It seems the fpu in question (fpv4-sp-d16) only
> supports 32 bit operations so this is somehow getting passed to a software
> wrapper and crashing there.  But to be fair this was crashing in gcc too
> which is why we added the -fsingle-precision-constant flag since we
didn't
> care about the precision of the constants and we're using floats
everywhere
> anyway for performance.
>
> Shouldn't the code generator know to make the constants 32-bit if
that's
> all the target supports? Or does it emulate 64-bit in software?

Yes I believe it is (trying to) emulate in software.  There's no
requirement to have an FPU at all so this is the expected behavior.
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