Submitted by Jerry DeLisle on Feb. 28, 2011, 1:18 a.m.

Message ID | 4D6AF7F7.6080509@frontier.com |
---|---|

State | New |

Headers | show |

Jerry DeLisle wrote: > Regression tested on x86-64. The comprehensive test case is from the > PR reporter, Thomas Henlich. Thanks Thomas for that test case. > OK for trunk? OK. Thanks for the patch. Tobias > 2011-02-27 Jerry DeLisle <jvdelisle@gcc.gnu.org> > > PR libgfortran/47567 > * io/write_float.def (output_float): Move handling of w = 0 to after > output rounding. Check for zero and set zero_flag accordingly. Set > width according to zero_flag. Add better comments.

On Sun, Feb 27, 2011 at 5:18 PM, Jerry DeLisle <jvdelisle@frontier.com> wrote: > Hi all, > > I am painfully aware that we have gone through a few iterations here. Once > again, I hope this is the last of it. > > This patch does some code clean-up. I have consolidated the handling of the > special case of F0.d in one place and moved the special case of zero values > to after rounding has occurred. This way, values not zero, but rounded down > to zero are handled correctly. > > Regression tested on x86-64. The comprehensive test case is from the PR > reporter, Thomas Henlich. Thanks Thomas for that test case. > > OK for trunk? > > Jerry > > 2011-02-27 Jerry DeLisle <jvdelisle@gcc.gnu.org> > > PR libgfortran/47567 > * io/write_float.def (output_float): Move handling of w = 0 to after > output rounding. Check for zero and set zero_flag accordingly. Set > width according to zero_flag. Add better comments. > It doesn't work. I opened: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47933

Index: write_float.def =================================================================== --- write_float.def (revision 170543) +++ write_float.def (working copy) @@ -109,16 +109,8 @@ output_float (st_parameter_dt *dtp, const fnode *f /* Make sure zero comes out as 0.0e0. */ if (zero_flag) - { - e = 0; - if (compile_options.sign_zero != 1) - sign = calculate_sign (dtp, 0); + e = 0; - /* Handle special cases. */ - if (w == 0) - w = d + (sign != S_NONE ? 2 : 1) + (d == 0 ? 1 : 0); - } - /* Normalize the fractional component. */ buffer[2] = buffer[1]; digits = &buffer[2]; @@ -376,15 +368,21 @@ output_float (st_parameter_dt *dtp, const fnode *f else edigits = 0; - /* Zero values always output as positive, even if the value was negative - before rounding. */ + /* Scan the digits string and count the number of zeros. If we make it + all the way through the loop, we know the value is zero after the + rounding completed above. */ for (i = 0; i < ndigits; i++) { if (digits[i] != '0') break; } + + /* To format properly, we need to know if the rounded result is zero and if + so, we set the zero_flag which may have been already set for + actual zero. */ if (i == ndigits) { + zero_flag = true; /* The output is zero, so set the sign according to the sign bit unless -fno-sign-zero was specified. */ if (compile_options.sign_zero == 1) @@ -393,11 +391,17 @@ output_float (st_parameter_dt *dtp, const fnode *f sign = calculate_sign (dtp, 0); } - /* Pick a field size if none was specified. */ + /* Pick a field size if none was specified, taking into account small + values that may have been rounded to zero. */ if (w <= 0) { - w = nbefore + nzero + nafter + (sign != S_NONE ? 2 : 1); - w = w == 1 ? 2 : w; + if (zero_flag) + w = d + (sign != S_NONE ? 2 : 1) + (d == 0 ? 1 : 0); + else + { + w = nbefore + nzero + nafter + (sign != S_NONE ? 2 : 1); + w = w == 1 ? 2 : w; + } } /* Work out how much padding is needed. */