[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879
--- Comment #12 from Sergei Trofimovich ---
(In reply to Jakub Jelinek from comment #5)
> It is the foperator_mult::op{1,2}_range and can be seen even on:
> double
> foo (double x, double y)
> {
> double z = x * y;
> if (z == 0.0)
> return x;
> return 42.0;
> }
> testcase.
> 2->3 (T) x_2(D) : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
> 2->3 (T) y_3(D) : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
> 2->3 (T) z_4 : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
> On the true edge of z == 0.0, we have [-0., 0.] range for z_4, that is
For my curiosity fow did you get such a detailed [frange] output for the
expressions? I tried -fdump-tree-all-all and best I get is a one-liner around
PHI nodes:
# RANGE [frange] double [0.0 (0x0.0p+0), +Inf]
# iftmp.5_6 = PHI
# .MEM_23 = PHI <.MEM_19(3), .MEM_19(4), .MEM_15(6)>
# VUSE <.MEM_23>
return iftmp.5_6;
Is there a magic gcc flag to dump more range details? Or you had to patch a bit
of gcc code?
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 --- Comment #11 from Martin Liška --- > I was sure the > server-side receive hook was supposed to reject such incomplete Changelog, > though? New files in test-suite are not mandatory by the hook and corresponding ChangeLog entries are generated automatically.
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 --- Comment #10 from Alexander Monakov --- If anyone is confused like I was, the commit actually includes a testcase, but the addition is not mentioned in the Changelog. I was sure the server-side receive hook was supposed to reject such incomplete Changelog, though?
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 Jakub Jelinek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #9 from Jakub Jelinek --- Fixed.
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 --- Comment #8 from CVS Commits --- The master branch has been updated by Jakub Jelinek : https://gcc.gnu.org/g:4500baaccb6e4d696e223c338bbdf7705c3646dd commit r13-4492-g4500baaccb6e4d696e223c338bbdf7705c3646dd Author: Jakub Jelinek Date: Mon Dec 5 11:17:42 2022 +0100 range-op-float: Fix up multiplication and division reverse operation [PR107879] While for the normal cases it seems to be correct to implement reverse multiplication (op1_range/op2_range) through division with float_binary_op_range_finish, reverse division (op1_range) through multiplication with float_binary_op_range_finish or (op2_range) through division with float_binary_op_range_finish, as e.g. following testcase shows for the corner cases it is incorrect. Say on the testcase we are doing reverse multiplication, we have [-0., 0.] range (no NAN) on lhs and VARYING on op1 (or op2). We implement that through division, because x from lhs = x * op2 is x = lhs / op2 For the division, [-0., 0.] / VARYING is computed (IMHO correctly) as [-0., 0.] +-NAN, because 0 / anything but 0 or NAN is still 0 and 0 / 0 is NAN and ditto 0 / NAN. And then we just float_binary_op_range_finish, which figures out that because lhs can't be NAN, neither operand can be NAN. So, the end range is [-0., 0.]. But that is not correct for the reverse multiplication. When the result is 0, if op2 can be zero, then x can be anything (VARYING), to be precise anything but INF (unless result can be NAN), because anything * 0 is 0 (or NAN for INF). While if op2 must be non-zero, then x must be 0. Of course the sign logic (signbit(x) = signbit(lhs) ^ signbit(op2)) still holds, so it actually isn't full VARYING if both lhs and op2 have known sign bits. And going through other corner cases one by one shows other differences between what we compute for the corresponding forward operation and what we should compute for the reverse operations. The following patch is slightly conservative and includes INF (in case of result including 0 and not NAN) in the ranges or 0 in the ranges (in case of result including INF and not NAN). The latter is what happens anyway because we flush denormals to 0, and the former just not to deal with all the corner cases. So, the end test is that for reverse multiplication and division op2_range the cases we need to adjust to VARYING or VARYING positive or VARYING negative are if lhs and op? ranges both contain 0, or both contain some infinity, while for division op1_range the corner case is if lhs range contains 0 and op2 range contains INF or vice versa. Otherwise I believe ranges from the corresponding operation are ok, or could be slightly more conservative (e.g. for reverse multiplication, if op? range is singleton INF and lhs range doesn't include any INF, then x's range should be UNDEFINED or known NAN (depending on if lhs can be NAN), while the division computes [-0., 0.] +-NAN; or similarly if op? range is only 0 and lhs range doesn't include 0, division would compute +INF +-NAN, or -INF +-NAN, or (for lack of multipart franges -INF +INF +-NAN just VARYING +-NAN), while again it is UNDEFINED or known NAN. Oh, and I found by code inspection wrong condition for the division's known NAN result, due to thinko it would trigger not just when both operands are known to be 0 or both are known to be INF, but when either both are known to be 0, or at least one is known to be INF. 2022-12-05 Jakub Jelinek PR tree-optimization/107879 * range-op-float.cc (foperator_mult::op1_range): If both lhs and op2 ranges contain zero or both ranges contain some infinity, set r range to zero_to_inf_range depending on signbit_known_p. (foperator_div::op2_range): Similarly for lhs and op1 ranges. (foperator_div::op1_range): If lhs range contains zero and op2 range contains some infinity or vice versa, set r range to zero_to_inf_range depending on signbit_known_p. (foperator_div::rv_fold): Fix up condition for returning known NAN.
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 --- Comment #7 from Sergei Trofimovich --- (In reply to Jakub Jelinek from comment #6) > Created attachment 53978 [details] > gcc13-pr107879.patch > > Untested fix. The patch fixed real ffmpeg-4 tests for me (before the change there were about 10 failures in resampler). Thank you!
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 Jakub Jelinek changed: What|Removed |Added Assignee|unassigned at gcc dot gnu.org |jakub at gcc dot gnu.org Status|NEW |ASSIGNED --- Comment #6 from Jakub Jelinek --- Created attachment 53978 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=53978=edit gcc13-pr107879.patch Untested fix.
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879
--- Comment #5 from Jakub Jelinek ---
It is the foperator_mult::op{1,2}_range and can be seen even on:
double
foo (double x, double y)
{
double z = x * y;
if (z == 0.0)
return x;
return 42.0;
}
testcase.
2->3 (T) x_2(D) : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
2->3 (T) y_3(D) : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
2->3 (T) z_4 : [frange] double [-0.0 (-0x0.0p+0), 0.0 (0x0.0p+0)]
On the true edge of z == 0.0, we have [-0., 0.] range for z_4, that is correct,
but getting from lhs [-0., 0.] and op2 range VARYING to [-0., 0.] is wrong.
We get that because we compute the range in that case as [-0., 0.] / VARYING,
and for division it is actually correct, [-0., 0.] divided by anything non-NAN
non-zero is still [-0., 0.], and [-0., 0.] divided by [-0., 0.] is NAN.
Plus we have the (IMHO still correct) implication that if a result is not NAN,
then neither operand could be NAN.
So I'm afraid back to the drawing board on when we can use division for
multiplication reverse ranges and when we can use multiplication for division
reverse ranges (and whether it is ok to use minus/plus for plus/minus reverse
operations).
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 Jakub Jelinek changed: What|Removed |Added CC||jakub at gcc dot gnu.org --- Comment #4 from Jakub Jelinek --- I will have a look.
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 Richard Biener changed: What|Removed |Added Priority|P3 |P1
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879
Sergei Trofimovich changed:
What|Removed |Added
CC||jakub at redhat dot com
--- Comment #3 from Sergei Trofimovich ---
If I did the bisection correctly `git bisect` points to
r13-3926-gd4c2f1d376da6f
commit d4c2f1d376da6fc3f3c30a9d3160e43c95399343
Author: Jakub Jelinek
Date: Sat Nov 12 09:39:00 2022 +0100
range-op: Implement op[12]_range operators for {PLUS,MINUS,MULT,RDIV}_EXPR
[Bug tree-optimization/107879] [13 Regression] ffmpeg-4 test suite fails on FPU arithmetics
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107879 Andrew Pinski changed: What|Removed |Added Keywords||wrong-code Target Milestone|--- |13.0 CC||aldyh at gcc dot gnu.org Status|UNCONFIRMED |NEW Last reconfirmed||2022-11-26 Ever confirmed|0 |1 Component|middle-end |tree-optimization --- Comment #2 from Andrew Pinski --- .
