[llvm-commits] [llvm] r40792 - in /llvm/trunk/lib/Target: Alpha/AlphaTargetMachine.cpp IA64/IA64TargetMachine.cpp PowerPC/PPCSubtarget.h Sparc/SparcTargetMachine.cpp TargetData.cpp X86/X86TargetMachine.cpp
Chris Lattner
clattner at apple.com
Fri Aug 3 17:05:53 PDT 2007
>>> + PPC_FP128TyID, ///< 5: 128 bit floating point type (two 64-
>>> bits)
>>
>> Is there a different name for this? PowerPC isn't the only platform
>> that
>> uses (or could use) a double-double approach.
>
> What other target does? I've no objection to renaming if you have a
> more descriptive suggestion
I agree this seems common too, and if we know of a target that has
it, we can pick a name. However, I also think it is reasonable to
just start out with this name and rename/generalize it down the road
if we find a need for it.
> (with a relatively short name - 80
> columns you know. Wonder how many LLVM hackers have ever seen a
> punched card....)
Poor Dale :)
>> Also, what LLVM instruction would be used for conversions between
>> this
>> type and the regular FP128 type?
>
> I don't see a short-term need to support this; they don't exist
> simultaneously on any target AFAIK.
Right, I think we can just define some convention and stick to it. I
don't expect to see code that does this in practice. We could just
define "ppc" 128-bit as smaller than IEEE 128-bit, since it is less
general, for example.
> (Having this target dependency
> in the IR is unfortunate, IMO; if there were a single "long double"
> type you couldn't even ask that question. But as long as the FEs are
> responsible for decimal->binary constant conversion we're stuck with
> it.)
Yep, not only that, but the middle-end needs to know how to constant
fold correctly etc.
-Chris
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