[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 Richard Biener changed: What|Removed |Added Keywords||missed-optimization Priority|P3 |P2
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603
Martin Sebor changed:
What|Removed |Added
Ever confirmed|0 |1
Status|UNCONFIRMED |NEW
Last reconfirmed||2022-03-01
CC||msebor at gcc dot gnu.org
--- Comment #8 from Martin Sebor ---
It looks like the problem is that the call to Base::operator==() might enter
infinite recursion. With the changed test case below GCC issues
-Winfinite-recursion pointing it out. With the original test case the infinite
recursion isn't inevitable but because it can't be ruled out GCC emits
(invalid) code that then triggers -Warray-bounds. It might be possible to do
better: detect the possible infinite recursion early and fold the equality to
false. (As far as I can see, that's what recent Clang seems to do.)
$ cat pr104603.C && gcc -O2 -S -Wall -fdump-tree-optimized=/dev/stdout
pr104603.C
struct Base {
bool isX_;
Base(bool isX = false) : isX_(isX) { }
bool isX() const { return isX_; }
bool operator==(const Base& rhs) const;
};
struct X : public Base {
X(const Base& b) : Base(true), b_(b) { }
bool operator==(const X& rhs) const { return b_ == rhs.b_; }
Base b_;
};
inline bool Base::operator==(const Base& rhs) const
{
return /* isX() && rhs.isX() && */ static_cast(*this) ==
static_cast(rhs);
}
Base base (true);
int main ()
{
return X(base) == X(base);
}
pr104603.C: In member function ‘bool X::operator==(const X&) const’:
pr104603.C:10:8: warning: infinite recursion detected [-Winfinite-recursion]
10 | bool operator==(const X& rhs) const { return b_ == rhs.b_; }
|^~~~
In member function ‘bool Base::operator==(const Base&) const’,
inlined from ‘bool X::operator==(const X&) const’ at pr104603.C:10:51:
pr104603.C:16:69: note: recursive call
16 | rn /* isX() && rhs.isX() && */ static_cast(*this) ==
static_cast(rhs);
|
~^
;; Function main (main, funcdef_no=9, decl_uid=2452, cgraph_uid=10,
symbol_order=10) (executed once)
Merging blocks 3 and 4
int main ()
{
[local count: 10631108]:
[local count: 1073741824]:
goto ; [100.00%]
}
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 --- Comment #7 from herumi --- Created attachment 52478 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=52478=edit an original code The array-bounds.zip file is a little stripped original issue. array-bounds% g++-11.2 -O2 -c a.cpp -Warray-bounds -save-temps
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 --- Comment #6 from Andrew Pinski --- (In reply to herumi from comment #5) > >Can you file a seperate issue with the preprocessed source (-save-temps) > >since it really does look like a seperate issue all together. > > May I attach a zipped a.ii which is generated by the following commands? Zipped is perfect.
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603
--- Comment #5 from herumi ---
>Can you file a seperate issue with the preprocessed source (-save-temps) since
>it really does look like a seperate issue all together.
May I attach a zipped a.ii which is generated by the following commands?
The size of a.ii is over 1700KiB.
---
>cat a.cpp
#include
using namespace Xbyak::util;
void f()
{
ptr[eax] == ptr[eax];
}
---
---
g++-11.2 -O2 -I ../ -Warray-bounds -c a.cpp -save-temps
---
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 --- Comment #4 from Andrew Pinski --- (In reply to herumi from comment #3) > The reason why I made this code is from the issue: > https://github.com/herumi/xbyak/issues/137 Can you file a seperate issue with the preprocessed source (-save-temps) since it really does look like a seperate issue all together. If it is not a seperate issue in the end, at least we recorded the issue with the original source.
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 --- Comment #3 from herumi --- >Also if this is from some larger code, >it might be useful to have the non-reduced testcase >since the reduced testcase might being showing something different. The reason why I made this code is from the issue: https://github.com/herumi/xbyak/issues/137
[Bug tree-optimization/104603] [10/11/12 Regression] wrong detection of -Warray-bounds for interesting tail resusive case
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104603 Andrew Pinski changed: What|Removed |Added Summary|wrong detection of g++ |[10/11/12 Regression] wrong |-Warray-bounds about|detection of |downcast|-Warray-bounds for ||interesting tail resusive ||case Component|c++ |tree-optimization Target Milestone|--- |10.4 --- Comment #2 from Andrew Pinski --- Someone else needs to look into this further than me because the warning only happens because there are cases where the access can happen but the accesses are not really used. Also if this is from some larger code, it might be useful to have the non-reduced testcase since the reduced testcase might being showing something different.
