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Re: Patch gcc-4.0 should not apply mathematical associative rules for addition or multiplication


Fariborz Jahanian <fjahanian@apple.com> writes:

| On Oct 5, 2004, at 1:53 PM, Geoff Keating wrote:
| 
| >>
| >> Wording of ANSIC disallows such foldings even if it is safe sometimes.
| >
| > Could you explain why you think the standard says this?  The quote
| > you gave said "In the following fragment, rearrangements suggested
| > by mathematical rules for real numbers are often not valid" but it
| > did not say that they were *always* not valid.
| 
| The section uses such words as 'often restricted', 'generally invalid'
| 'cannot generally replace'. So, I posed this as
| the question and consensus was that we should place this under
| -funsafe-math-optimizations flag. Almost all
| optimization placed under above flag is 'sometimes' valid and yet we
| place them under this flag.

Yes, and that is what we agreed on after repeated long debates.

| I don't see a difference in this case.

Right.

-- Gaby


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