std::rotate fails in some cases due to std::memmove

[Daniele Di Proietto]

Testcase attached

I've noticed a weird failure of std::rotate(first, middle, last) that happens when middle == last - 1, i.e. when trying to rotate_right.

The library has a special case for that: it detects that we are rotating right and __rotate_right gets called (algorithm:2325)

__rotate_right moves the last element in the first place and then tries to move all the other elements forwards by one position by calling move_backward (algorithm:1897)

There are different versions of move_backward: one of them is selected based on the result of a __unwrap_iter (algorithm:1674).

In this case __move_backward (algorithm:1885) gets called: this version deals with memory pointers, and calls std::memmove to actually move objects. This some how fails

One of the possible solutions would probably be to remove __unwrap_iter that returns a pointer and deal always with iterators.

[Daniele Di Proietto (d-diproietto)]

There appears to be a bug in memmove (testcase attached)

the generated code is:

Lv[1] = Lv[0];
Lv.set(Lv.subarray(0,3),1);

where Lv is the v vector. The first line is harmful: it is generated by DuettoWriter.cpp:467 to translate a @llvm.memcpy.p0i8.p0i8.i32.
Unfortunately I'm not very familiar with duetto internals so, this is as far as I can get.

[Alessandro Pignotti (a-pignotti)]

I believe https://github.com/leaningtech/duetto-llvm/commit/c61fe56a0e4e5110d423a4b8ccbbf97e089a5fc6 fixes the issue