[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 Marek Polacek changed: What|Removed |Added Status|ASSIGNED|RESOLVED Resolution|--- |FIXED --- Comment #9 from Marek Polacek --- Fixed for GCC 8.
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 Marek Polacek changed: What|Removed |Added Status|NEW |ASSIGNED Assignee|unassigned at gcc dot gnu.org |mpolacek at gcc dot gnu.org
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 --- Comment #8 from Marek Polacek --- Author: mpolacek Date: Wed Jul 26 11:53:17 2017 New Revision: 250566 URL: https://gcc.gnu.org/viewcvs?rev=250566=gcc=rev Log: PR middle-end/70992 * tree.c (build2_stat): Don't set TREE_CONSTANT on divisions by zero. * gcc.dg/overflow-warn-1.c: Adjust dg-error. * gcc.dg/overflow-warn-2.c: Likewise. * gcc.dg/overflow-warn-3.c: Likewise. * gcc.dg/overflow-warn-4.c: Likewise. * gcc.dg/torture/pr70992-2.c: New test. * gcc.dg/torture/pr70992.c: New test. Added: trunk/gcc/testsuite/gcc.dg/torture/pr70992-2.c trunk/gcc/testsuite/gcc.dg/torture/pr70992.c Modified: trunk/gcc/ChangeLog trunk/gcc/testsuite/ChangeLog trunk/gcc/testsuite/gcc.dg/overflow-warn-1.c trunk/gcc/testsuite/gcc.dg/overflow-warn-2.c trunk/gcc/testsuite/gcc.dg/overflow-warn-3.c trunk/gcc/testsuite/gcc.dg/overflow-warn-4.c trunk/gcc/tree.c
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 --- Comment #7 from Marek Polacek --- We can simply do: --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -9387,6 +9387,11 @@ fold_binary_loc (location_t loc, TREE_TYPE (arg0), arg0, cst0)); } + /* Adding anything to a division-by-zero makes no sense and +can confuse extract_muldiv and fold_plusminus_mult_expr. */ + else if (TREE_CODE (arg0) == TRUNC_DIV_EXPR + && integer_zerop (TREE_OPERAND (arg0, 1))) + return fold_convert_loc (loc, type, arg0); } /* Handle (A1 * C1) + (A2 * C2) with A1, A2 or C1, C2 being the same or (In reply to Alexander Monakov from comment #6) > We can simply fold A / 0 * B and A / 0 + B to 1 / 0 or 0 / 0. > > I wonder why fold_plusminus_mult_expr puts the addition inside, that doesn't > appear useful? fold_plusminus_mult_expr tries to turn e.g. 2*a + a into 3*a, so that's where the + 1 comes from.
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 Alexander Monakov changed: What|Removed |Added CC||amonakov at gcc dot gnu.org --- Comment #6 from Alexander Monakov --- We can simply fold A / 0 * B and A / 0 + B to 1 / 0 or 0 / 0. I wonder why fold_plusminus_mult_expr puts the addition inside, that doesn't appear useful?
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 Marek Polacek changed: What|Removed |Added CC||mpolacek at gcc dot gnu.org --- Comment #5 from Marek Polacek --- I can confirm that even Comment 4 is the same extract_muldiv_1 <-> fold_plusminus_mult_expr issue: ((2147483648 / 0) * 2) + 2 <-> 2 * (2147483648 / 0 + 1) So the question is: where should we break the tie?
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992
Arseny Solokha changed:
What|Removed |Added
Known to fail||8.0
--- Comment #4 from Arseny Solokha ---
The following makes gcc-8.0.0-alpha20170709 snapshot ICE w/ no command line
options at all:
typedef unsigned int uint32_t;
uint32_t
ls (uint32_t so)
{
return (so + so) * (0x8000 / 0 + 1);
}
% gcc-8.0.0-alpha20170709 -c -w sxijy9dr.c
x86_64-unknown-linux-gnu-gcc-8.0.0-alpha20170709: internal compiler error:
Segmentation fault (program cc1)
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 --- Comment #3 from Richard Biener --- The bad recursion happens between extract_muldiv_1 /* The last case is if we are a multiply. In that case, we can apply the distributive law to commute the multiply and addition if the multiplication of the constants doesn't overflow and overflow is defined. With undefined overflow op0 * c might overflow, while (op0 + orig_op1) * c doesn't. */ if (code == MULT_EXPR && TYPE_OVERFLOW_WRAPS (ctype)) return fold_build2 (tcode, ctype, fold_build2 (code, ctype, fold_convert (ctype, op0), fold_convert (ctype, c)), op1); which does (0 % 0 + 1) * 2 -> (0 % 0) * 2 + 2 and the reverse transformation fold_plusminus_mult_expr does.
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 --- Comment #2 from Richard Biener --- I think the issue is that the associate case treats (0 % 0 + 1) * 2 as constant but that gets further "simplified" when combined with the rest. In the end our refusal to simplify 0 % 0 to 0 causes things to go downhill (we _do_ simplify 0 % a to 0!) (for mod (ceil_mod floor_mod round_mod trunc_mod) /* 0 % X is always zero. */ (simplify (mod integer_zerop@0 @1) /* But not for 0 % 0 so that we can get the proper warnings and errors. */ (if (!integer_zerop (@1)) @0))
[Bug middle-end/70992] Infinite recursion between fold_build2_stat_loc and fold_binary_loc w/ -fwrapv
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70992 Richard Biener changed: What|Removed |Added Keywords|ice-on-invalid-code |ice-on-valid-code Status|UNCONFIRMED |NEW Last reconfirmed||2016-05-09 Version|unknown |6.1.0 Ever confirmed|0 |1 Known to fail||4.3.5 --- Comment #1 from Richard Biener --- Confirmed back to GCC 4.3.
