https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103037
--- Comment #8 from Richard Biener <rguenth at gcc dot gnu.org> ---
More reduced testcase - the min() obfuscation is to avoid recognizing a
MIN_EXPR before jump threading gets the chance to disrupt it. A GIMPLE unit
testcase for
PRE is difficult since we are not supporting SSA annotations (ranges) at the
moment.
static inline const unsigned short *
min(unsigned short *d, const unsigned short *e)
{
return *e < *d ? e : d;
}
unsigned short __attribute__((noipa))
test(unsigned short arr, unsigned short val)
{
unsigned short tem = 1;
unsigned short tem2 = *min(&arr, &tem);
return tem2 / (arr ? arr : val);
}
int
main()
{
if (test (2, 2) != 0)
__builtin_abort();
return 0;
}
The IL for the reduced testcase before PRE is
<bb 2> [local count: 1073741824]:
if (arr_6(D) > 1)
goto <bb 4>; [50.00%]
else
goto <bb 3>; [50.00%]
<bb 3> [local count: 536870912]:
# RANGE [0, 1] NONZERO 1
_1 = (int) arr_6(D); // (A)
if (arr_6(D) != 0)
goto <bb 4>; [20.00%]
else
goto <bb 5>; [80.00%]
<bb 4> [local count: 536870913]:
# RANGE [0, 1] NONZERO 1
# _17 = PHI <_1(3), 1(2)>
# RANGE [1, 65535] NONZERO 65535
iftmp.0_9 = (int) arr_6(D); // (B)
goto <bb 6>; [100.00%]
<bb 5> [local count: 536870913]:
# RANGE [0, 65535] NONZERO 65535
iftmp.0_8 = (int) val_7(D);
<bb 6> [local count: 1073741824]:
# RANGE [0, 65535] NONZERO 65535
# iftmp.0_3 = PHI <iftmp.0_9(4), iftmp.0_8(5)>
# RANGE [0, 1] NONZERO 1
# _18 = PHI <_17(4), 0(5)>
# RANGE [0, 1] NONZERO 1
_2 = _18 / iftmp.0_3;
# RANGE [0, 1] NONZERO 1
_10 = (short unsigned int) _2;
return _10;
and the problematic value-numbering is
iftmp.0_9 = _1 (0001)
at (A) and (B). By design we may only use _available_ expressions during
simplification but _1 is not available on the 4 -> 6 edge. That's working
OK for the translation from 4 -> 6 but then we record a valueized
expression into the ANTIC set of 4 which when further translated and
simplified has the wrong representative inside.
