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[Bug target/33391] [4.3 regression] gfortran.dg/do_3.F90 fails at -O2
- From: "burnus at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 11 Sep 2007 15:34:05 -0000
- Subject: [Bug target/33391] [4.3 regression] gfortran.dg/do_3.F90 fails at -O2
- References: <firstname.lastname@example.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from burnus at gcc dot gnu dot org 2007-09-11 15:34 -------
> > -fstrict-overflow
> > Allow the compiler to assume strict signed overflow rules, depending on the
> > language being compiled.
> Well, I think the "depending on the language being compiled" is important. I
> think the testcase is valid Fortran, and shouldn't fail whatever the
> optimization level you use.
I'm not sure; for -O2 maybe not but for -O3? If one takes overflows (integer,
floating point variables), +/-Inf, NaN (only fp) fully into account, many
optimizations are no longer possible.
Example: "if (i + 10 > 20)"; should this be optimized to "if(i > 10)" or not?
And if yes, starting from which optimization level?
See also (for FP math):