https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88240
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |rguenth at gcc dot gnu.org
Component|other |tree-optimization
Depends on| |86554
--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
The following culd be massaged into a testcase:
int flag;
union { float f; int i; } u;
int main()
{
if (flag)
__builtin_printf("%d", u.i);
else
__builtin_printf("%f", u.f);
return 0;
}
It is PRE / code hoisting that hoists the loaded value (and it chooses the
float variant). -fno-code-hoisting should mitigate this. PR86554 is a
related issue.
main ()
{
int flag.0_1;
double _4;
float pretmp_10;
int _11;
<bb 2> [100.00%]:
flag.0_1 = flag;
pretmp_10 = u.f;
if (flag.0_1 != 0)
goto <bb 3>; [46.00%]
else
goto <bb 4>; [54.00%]
<bb 3> [46.00%]:
_11 = VIEW_CONVERT_EXPR<int>(pretmp_10);
__builtin_printf ("%d", _11);
goto <bb 5>; [100.00%]
<bb 4> [54.00%]:
_4 = (double) pretmp_10;
__builtin_printf ("%f", _4);
Given the intention of the optimization is to CSE loading the memory contents
and we elsewhere avoid using floats for such operation the bug is probably
valid.
Referenced Bugs:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86554
[Bug 86554] [7/8/9 Regression] Incorrect code generation with signed/unsigned
comparison
