https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90020
--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
So looking at one issue I can see is code-hoisting hoisting
MEM[(struct window *)window_6(D) + -5B].contents across a call that might
not return. This can only happen for calls we can alias-disambiguate
against which means in this case pure calls. For example for divisions
we guard against this case my checking whether it may trap and there
was an earlier call that might not return. That is missing for memory
referneces.
<bb 2> [local count: 1073741824]:
# VUSE <.MEM_5(D)>
_1 = WINDOWP (window_6(D));
if (_1 != 0)
goto <bb 3>; [50.00%]
else
goto <bb 4>; [50.00%]
<bb 3> [local count: 536870913]:
# VUSE <.MEM_5(D)>
_2 = MEM[(struct window *)window_6(D) + -5B].contents;
# VUSE <.MEM_5(D)>
_3 = BUFFERP (_2);
_8 = (int) _3;
<bb 4> [local count: 1073741824]:
# iftmp.1_4 = PHI <_8(3), 0(2)>
# VUSE <.MEM_5(D)>
CHECK_TYPE (iftmp.1_4, 4856B, window_6(D));
# VUSE <.MEM_5(D)>
_7 = MEM[(struct window *)window_6(D) + -5B].contents;
# VUSE <.MEM_5(D)>
return _7;
But fixing that on the GIMPLE level doesn't make the issue go away since
we have similar functionality on RTL which triggers (and is the older
issue since GIMPLE can do hoisting only since GCC 7).
