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[LangRef] describe the default FP environment
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Authored by spatel on Mar 9 2018, 10:30 AM.

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Summary

Follow-up for @lattner's suggestion in D44216: add a section and examples to describe the FP env.

I thought about mentioning IEEE-754 here, but I don't know how far we can or want to go in that direction.

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spatel created this revision.Mar 9 2018, 10:30 AM
efriedma added inline comments.Mar 9 2018, 2:29 PM
docs/LangRef.rst
2300

Using undef here is confusing, since it's not any specific value. If you want an SNaN, write an SNaN.

spatel updated this revision to Diff 138057.Mar 12 2018, 10:57 AM

Patch updated:

  1. Fix example to show SNaN explicitly.
  2. Remove duplicate text from the opcode definitions. Now that we have a description of the environment, we can just point to it. Presumably, we'll do the same for non-constrained FP intrinsics, but I'll double-check those and make another patch.
scanon accepted this revision.Mar 20 2018, 8:05 AM

I'm OK with this.

This revision is now accepted and ready to land.Mar 20 2018, 8:05 AM

I'm OK with this.

LGTM too.

I thought about mentioning IEEE-754 here, but I don't know how far we can or want to go in that direction.

I wouldn't mind doing this. We do, in fact, assume IEEE-754 representation (except for in special types) and we probably should document that.

I thought about mentioning IEEE-754 here, but I don't know how far we can or want to go in that direction.

I wouldn't mind doing this. We do, in fact, assume IEEE-754 representation (except for in special types) and we probably should document that.

Great - thanks for clarifying that. We'd be in big trouble with existing folds if that wasn't true. :)
I'll commit this as-is and enhance in follow-ups.

This revision was automatically updated to reflect the committed changes.