Module: ppl/ppl Branch: floating_point Commit: a69cc00cdd67f30135df670f9ebb4b2061c9fb35 URL: http://www.cs.unipr.it/git/gitweb.cgi?p=ppl/ppl.git;a=commit;h=a69cc00cdd67f... Author: Fabio Bossi <bossi@cs.unipr.it> Date: Fri Jul 30 16:04:19 2010 +0200 Avoid adding errors when casting to a more precise floating point format. --- src/Float.defs.hh | 6 ++++++ src/Float.inlines.hh | 6 +++++- src/linearize.hh | 13 ++++++++++--- 3 files changed, 21 insertions(+), 4 deletions(-) diff --git a/src/Float.defs.hh b/src/Float.defs.hh index e484458..75d2c2b 100644 --- a/src/Float.defs.hh +++ b/src/Float.defs.hh @@ -361,6 +361,12 @@ public: #endif /*! \brief + Returns <CODE>true</CODE> if and only if there is some floating point + number that is representable by \p f2 but not by \p f1. +*/ +bool is_less_precise_than(Floating_Point_Format f1, Floating_Point_Format f2); + +/*! \brief Computes the absolute error of floating point computations. \par Template type parameters diff --git a/src/Float.inlines.hh b/src/Float.inlines.hh index 16e0f21..13692b8 100644 --- a/src/Float.inlines.hh +++ b/src/Float.inlines.hh @@ -444,6 +444,11 @@ float_ieee754_quad::build(bool negative, mpz_t mantissa, int exponent) { << (MANTISSA_BITS - 64); } +inline bool +is_less_precise_than(Floating_Point_Format f1, Floating_Point_Format f2) { + return f1 < f2; +} + #if PPL_SUPPORTED_FLOAT inline Float<float>::Float() { @@ -492,7 +497,6 @@ Float<long double>::value() { } #endif - } // namespace Parma_Polyhedra_Library #endif // !defined(PPL_Float_inlines_hh) diff --git a/src/linearize.hh b/src/linearize.hh index a4f131d..0093586 100644 --- a/src/linearize.hh +++ b/src/linearize.hh @@ -616,16 +616,23 @@ cast_linearize(const Cast_Operator<Target>& cast_expr, typedef Box<FP_Interval_Type> FP_Interval_Abstract_Store; typedef std::map<dimension_type, FP_Linear_Form> FP_Linear_Form_Abstract_Store; + Floating_Point_Format analyzed_format = + cast_expr.type().floating_point_format(); const Concrete_Expression<Target>* cast_arg = cast_expr.argument(); if (cast_arg->type().is_floating_point()) { if (!linearize(*cast_arg, int_store, lf_store, result)) return false; + if (!is_less_precise_than(analyzed_format, + cast_arg->type().floating_point_format())) + // We are casting to a more precise format. Do not add errors. + return true; } - else + else { result = FP_Linear_Form(FP_Interval_Type(cast_arg->get_integer_interval())); + /* FIXME: we can avoid adding errors if FP_Interval_Type::boundary_type + is less precise than analyzed_format. */ + } - Floating_Point_Format analyzed_format = - cast_expr.type().floating_point_format(); FP_Linear_Form rel_error; result.relative_error(analyzed_format, rel_error); result += rel_error;