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



On 05/10/2004, at 1:12 PM, Gabriel Dos Reis wrote:


Geoffrey Keating <geoffk@geoffk.org> writes:

[...]

| > + static inline bool
| > + associative_fp_binop (tree exp)
| > + {
| > +   enum tree_code code = TREE_CODE (exp);
| > +   return !(!flag_unsafe_math_optimizations
|
| This flag is not clearly the right one.  Why did you pick it from the
| alternatives?

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?

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