https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118509
Bug ID: 118509
Summary: Front-end produced uninitialized memory reference when
compiling Nektar
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: dizhao at os dot amperecomputing.com
Target Milestone: ---
Created attachment 60170
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=60170&action=edit
preprocessed cpp code
The problem is found when building Nektar++:
https://gitlab.nektar.info/nektar/nektar, file
library/LocalRegions/QuadExp.cpp .
Attached is a preprocessed version of the code, so it would be
easier to reproduce the problem. (Sorry the source file has a
big 2Mb size, I've tried to remove some codes, but it's rather
difficult and time consuming to go on with that...) The compile
option is "g++ -std=c++17 -Ofast -c".
The bug is exposed after commit b25d3201 (gcc-15), On function:
"struct shared_ptr
std::__invoke_impl<std::shared_ptr<Nektar::NekMatrix<Nektar::NekMatrix<Nektar::NekMatrix<double,
Nektar::StandardMatrixTag>, Nektar::ScaledMatrixTag>, Nektar::BlockMatrixTag>
>,
std::shared_ptr<Nektar::NekMatrix<Nektar::NekMatrix<Nektar::NekMatrix<double,
Nektar::StandardMatrixTag>, Nektar::ScaledMatrixTag>, Nektar::BlockMatrixTag> >
(Nektar::LocalRegions::Expansion::*&)(const Nektar::LocalRegions::MatrixKey&),
Nektar::LocalRegions::QuadExp*&, const Nektar::LocalRegions::MatrixKey&>
(struct ..."
.
After this commit, the gimple code at 007.gimple is like:
...
struct QuadExp * D.278923; //The problematic pointer.
D.271234 = MEM[(struct QuadExp * &)__t];
D.271235 = *__f;
_1 = D.271235.__delta;
_2 = _1 & 1;
if (_2 != 0) goto <D.278921>; else goto <D.278922>;
<D.278921>:
D.278923 = D.271234; //Assigned in one of the if-else branch.
_3 = D.271235.__delta;
_4 = _3 >> 1;
_5 = (sizetype) _4;
_6 = D.278923->D.217872._vptr.StdExpansion2D;
_7 = _6 + 18446744073709551472;
_8 = MEM[(long int *)_7];
_9 = (sizetype) _8;
_10 = _5 + _9;
_11 = D.278923 + _10;
_12 = MEM[(int (*) () * *)_11];
_13 = D.271235.__pfn;
_14 = (sizetype) _13;
_15 = _12 + _14;
iftmp.53 = *_15;
goto <D.278924>;
<D.278922>:
iftmp.53 = D.271235.__pfn;
<D.278924>:
iftmp.54_16 = iftmp.53;
_17 = D.271235.__delta;
_18 = _17 >> 1;
_19 = (sizetype) _18;
_20 = D.278923->D.217872._vptr.StdExpansion2D; //Used after if-else.
_21 = _20 + 18446744073709551472;
_22 = MEM[(long int *)_21];
_23 = (sizetype) _22;
_24 = _19 + _23;
_25 = D.278923 + _24;
*<retval> = iftmp.54_16 (_25, __args#0); [return slot optimization]
return <retval>;
While before the commit, the gimple code was like:
D.379618 = MEM[(struct QuadExp * &)__t]; //Only this variable is used.
D.379620 = *__f;
_1 = D.379620.__delta;
_2 = _1 & 1;
if (_2 != 0) goto <D.379621>; else goto <D.379622>;
<D.379621>:
_3 = D.379620.__delta;
_4 = _3 >> 1;
_5 = (sizetype) _4;
_6 = D.379618->D.283369.D.273899._vptr.StdExpansion2D;
_7 = _6 + 18446744073709551096;
_8 = MEM[(long int *)_7];
_9 = (sizetype) _8;
_10 = _5 + _9;
_11 = D.379618 + _10;
_12 = MEM[(int (*) () * *)_11];
_13 = D.379620.__pfn;
_14 = (sizetype) _13;
_15 = _12 + _14;
iftmp.82 = *_15;
goto <D.379623>;
<D.379622>:
iftmp.82 = D.379620.__pfn;
<D.379623>:
iftmp.83_16 = iftmp.82;
_17 = D.379620.__delta;
_18 = _17 >> 1;
_19 = (sizetype) _18;
_20 = D.379618->D.283369.D.273899._vptr.StdExpansion2D;
_21 = _20 + 18446744073709551096;
_22 = MEM[(long int *)_21];
_23 = (sizetype) _22;
_24 = _19 + _23;
_25 = D.379618 + _24;
*<retval> = iftmp.83_16 (_25, __args#0); [return slot optimization]
return <retval>;
