[cfe-commits] [llvm-commits] [PATCH] Add llvm.fmuladd intrinsic.

Chandler Carruth chandlerc at google.com
Tue Jun 5 14:38:36 PDT 2012

On Tue, Jun 5, 2012 at 2:35 PM, Stephen Canon <scanon at apple.com> wrote:

> On Jun 5, 2012, at 2:31 PM, Chandler Carruth <chandlerc at google.com> wrote:
> On Tue, Jun 5, 2012 at 2:15 PM, Stephen Canon <scanon at apple.com> wrote:
> The trouble I see with this is that you're going to end up generating an
>> enormous number of start/stop intrinsics for some code (one pair for every
>> source expression containing FP, effectively).  I'm not sure how much of a
>> concern that really is, but it feels inelegant to me.
> My idea was essentially that you would only do this where contraction was
> precluded, which you indicated should be rare (1%). That should restrict
> the amount of start/stop churn?
> Are you imagining something completely different?
> Contraction is precluded across expression boundaries in the standard C
> numerics model.  Assuming we want to support standard C numerics, you would
> need to insert start/stop for every expression containing FP.

AH! So when you indicated only 1% would need to turn the pragma to off, it
was because the 99% case rely entirely on the source expression
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