On Mon, Feb 5, 2018 at 10:47 AM, Rainer Orth
<r...@cebitec.uni-bielefeld.de> wrote:
>
>> This patch to the Go frontend checks for negative numbers with very
>> small magnitudes that will round to negative zero, and forces them to
>> positive zero instead. This implements the spec clarification in
>> https://golang.org/cl/14727. The test is in
>> https://golang.org/cl/91895. This fixes golang.org/issue/12621.
>> Bootstrapped and ran Go testsuite on x86_64-pc-linux-gnu. Committed
>> to mainline.
>
> unfortunately, this broke bootstrap with mpfr 2.4.2, which is still the
> minimum version documented in install.texi:
Bother. Thanks for the note. I've rolled back the patch, as follows.
Ian
Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE (revision 257390)
+++ gcc/go/gofrontend/MERGE (working copy)
@@ -1,4 +1,4 @@
-7eebd495df915ab87926b8dd88f554674cfdacea
+c02c71187c9794b50444e2858c582e66a3442ee8
The first line of this file holds the git revision number of the last
merge done from the gofrontend repository.
Index: gcc/go/gofrontend/expressions.cc
===================================================================
--- gcc/go/gofrontend/expressions.cc (revision 257390)
+++ gcc/go/gofrontend/expressions.cc (working copy)
@@ -16158,16 +16158,10 @@ Numeric_constant::set_float(Type* type,
this->clear();
this->classification_ = NC_FLOAT;
this->type_ = type;
-
// Numeric constants do not have negative zero values, so remove
// them here. They also don't have infinity or NaN values, but we
// should never see them here.
- int bits = 0;
- if (type != NULL
- && type->float_type() != NULL
- && !type->float_type()->is_abstract())
- bits = type->float_type()->bits();
- if (Numeric_constant::is_float_zero(val, bits))
+ if (mpfr_zero_p(val))
mpfr_init_set_ui(this->u_.float_val, 0, GMP_RNDN);
else
mpfr_init_set(this->u_.float_val, val, GMP_RNDN);
@@ -16181,50 +16175,8 @@ Numeric_constant::set_complex(Type* type
this->clear();
this->classification_ = NC_COMPLEX;
this->type_ = type;
-
- // Avoid negative zero as in set_float.
- int bits = 0;
- if (type != NULL
- && type->complex_type() != NULL
- && !type->complex_type()->is_abstract())
- bits = type->complex_type()->bits() / 2;
-
- mpfr_t real;
- mpfr_init_set(real, mpc_realref(val), GMP_RNDN);
- if (Numeric_constant::is_float_zero(real, bits))
- mpfr_set_ui(real, 0, GMP_RNDN);
-
- mpfr_t imag;
- mpfr_init_set(imag, mpc_imagref(val), GMP_RNDN);
- if (Numeric_constant::is_float_zero(imag, bits))
- mpfr_set_ui(imag, 0, GMP_RNDN);
-
mpc_init2(this->u_.complex_val, mpc_precision);
- mpc_set_fr_fr(this->u_.complex_val, real, imag, MPC_RNDNN);
-
- mpfr_clear(real);
- mpfr_clear(imag);
-}
-
-// Return whether VAL, at a precision of BITS, is zero. BITS may be
-// zero in which case it is ignored.
-
-bool
-Numeric_constant::is_float_zero(const mpfr_t val, int bits)
-{
- if (mpfr_zero_p(val))
- return true;
- switch (bits)
- {
- case 0:
- return false;
- case 32:
- return mpfr_get_flt(val, GMP_RNDN) == 0;
- case 64:
- return mpfr_get_d(val, GMP_RNDN) == 0;
- default:
- go_unreachable();
- }
+ mpc_set(this->u_.complex_val, val, MPC_RNDNN);
}
// Get an int value.
Index: gcc/go/gofrontend/expressions.h
===================================================================
--- gcc/go/gofrontend/expressions.h (revision 257390)
+++ gcc/go/gofrontend/expressions.h (working copy)
@@ -4220,9 +4220,6 @@ class Numeric_constant
bool
check_complex_type(Complex_type*, bool, Location);
- static bool
- is_float_zero(const mpfr_t, int bits);
-
// The kinds of constants.
enum Classification
{
