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*From*: Gabriel Dos Reis <gdr at cs dot tamu dot edu>*To*: Geoff Keating <geoffk at geoffk dot org>*Cc*: Dale Johannesen <dalej at apple dot com>,Fariborz Jahanian <fjahanian at apple dot com>,GCC Patches <gcc-patches at gcc dot gnu dot org>*Date*: 05 Oct 2004 16:50:07 -0500*Subject*: Re: Patch gcc-4.0 should not apply mathematical associative rules for addition or multiplication*Organization*: Texas A&M University, Department of Computer Science*References*: <2B2F21A1-16FF-11D9-957B-000A95BA54A6@apple.com><m28yalosbv.fsf@greed.local> <m3sm8sorfl.fsf@merlin.cs.tamu.edu><B829D438-1710-11D9-BB5A-000A95B1F520@geoffk.org><C6712220-1712-11D9-A3AB-000A95D7CD40@apple.com><028CC984-1718-11D9-BB5A-000A95B1F520@geoffk.org>

Geoff Keating <geoffk@geoffk.org> writes: | On 05/10/2004, at 2:08 PM, Dale Johannesen wrote: | | > On 05/10/2004, at 1:12 PM, Gabriel Dos Reis wrote: | >> | >>> Geoffrey Keating <geoffk@geoffk.org> writes: | >>> That flag is clearly the right flag to pick. See the explanation | >>> he gave. | >>> It contains an example that illustrates the problem too. | >> | >> Fariborz said | >> | >>> For different values of "x" this leads to undeserved or absent | >>> floating point exceptions | >> | >> So, why not flag_trapping_math? The case involves an infinity, | >> what about flag_finite_math_only? | > | > It is not just exceptions. It is possible that X* (C*C) would | > overflow, or lose some low-order bits, | > where (X*C)*C would not, for large C and small X. | | OK. I am not going to re-design Fariborz's patch for him in an e-mail | exchange. It is clear that the explanation of the patch is inadequate | to determine whether or not the patch is correct, so the patch is | rejected. Fariborz, please re-post the patch with a better | explanation, and addressing the other points I mentioned. Which other points? (1) clearly, flag_finite_math_only is not adquate (2) clearly, flag_trapping_math is not adequate (3) clearly, testing both is not adequate I found his explanation rather clear, as to what the root of the problem is. Your reaction is rather difficult to follow. -- Gaby

**References**:**Patch gcc-4.0 should not apply mathematical associative rules for addition or multiplication***From:*Fariborz Jahanian

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

**Re: Patch gcc-4.0 should not apply mathematical associative rules for addition or multiplication***From:*Gabriel Dos Reis

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

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

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

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