https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106931
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[12/13 Regression] |[12/13 Regression]
|-Wstringop-overflow false |-Wstringop-overflow false
|positive -O3 |positive -O3
|-fno-tree-vectorize since |-fno-tree-vectorize with
|r12-3300-gece28da924ddda8b |loop unrolling since
| |r12-3300-gece28da924ddda8b
--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The false positive is issued for the store to A[i_90] in BB 10 by the strlen
pass, where i_90's range is [8, 8].
<bb 10> [local count: 712060]:
_35 = (sizetype) i_90;
_36 = B.1_83 + _35;
_37 = *_36;
A[i_90] = _37; << -Wstringop-overflow
_20 = _93 + 9;
i_39 = (int) _20;
goto <bb 12>; [100.00%]
Changing i's type to unsigned avoids the warning. The IL looks very close but
i_90's range in BB 10 is VR_UNDEFINED instead.
The following is debug_ranger() output for BBs 9 and 10 in the original test
case.
=========== BB 9 ============
Imports: _93
Exports: _8 i_90 _93
_8 : _93(I)
_86 : i_82(I)
_87 : i_82(I) B.1_83(I) _86
i_90 : _8 _93(I)
i_82 [irange] int [7, 7] NONZERO 0x7
_93 [irange] unsigned int [0, 0] NONZERO 0x0
Relational : (_8 > _93)
<bb 9> [local count: 801058]:
_86 = (sizetype) i_82;
_87 = B.1_83 + _86;
_88 = *_87;
A[i_82] = _88;
_8 = _93 + 8;
i_90 = (int) _8;
if (i_90 != 8)
goto <bb 10>; [88.89%]
else
goto <bb 12>; [11.11%]
_8 : [irange] unsigned int [8, 8] NONZERO 0x8
_86 : [irange] sizetype [7, 7] NONZERO 0x7
_87 : [irange] char * [1, +INF]
i_90 : [irange] int [8, 8] NONZERO 0x8
9->10 (T) _8 : [irange] UNDEFINED
9->10 (T) i_90 : [irange] UNDEFINED
9->10 (T) _93 : [irange] UNDEFINED
9->12 (F) _8 : [irange] unsigned int [8, 8] NONZERO 0x8
9->12 (F) i_90 : [irange] int [8, 8] NONZERO 0x8
9->12 (F) _93 : [irange] unsigned int [0, 0] NONZERO 0x0
=========== BB 10 ============
_93 [irange] UNDEFINED
<bb 10> [local count: 712060]:
_35 = (sizetype) i_90;
_36 = B.1_83 + _35;
_37 = *_36;
A[i_90] = _37;
_20 = _93 + 9;
i_39 = (int) _20;
goto <bb 12>; [100.00%]
whereas for the unsigned case:
=========== BB 10 ============
_85 [irange] UNDEFINED
i_90 [irange] UNDEFINED
