https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111779
Richard Biener <rguenth at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Component|c |tree-optimization
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
CC| |jamborm at gcc dot gnu.org
Last reconfirmed| |2023-10-12
--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
The issue is the aggregate copy:
t.c:26:22: missed: not vectorized: more than one data ref in stmt: a = *_3;
which SRA fails to scalarize:
<bb 3> [local count: 955630224]:
# s_23 = PHI <s_18(3), 0(2)>
# i_25 = PHI <i_20(3), 0(2)>
_1 = (long unsigned int) i_25;
_2 = _1 * 24;
_3 = x_16(D) + _2;
a = *_3;
_4 = BIT_FIELD_REF <a.b4, 8, 64>;
_12 = _4 & 1;
_6 = (int) _12;
s_18 = _6 + s_23;
a ={v} {CLOBBER(eol)};
i_20 = i_25 + 1;
if (y_14(D) > i_20)
Candidate (2778): a
...
! Disqualifying a - No scalar replacements to be created.
the BIT_FIELD_REF is already created by early folding in
optimize_bit_field_compare folding (int) a.b4.f != 0
s = ((int) NON_LVALUE_EXPR <BIT_FIELD_REF <a.b4, 8, 64>> & 1) + s;
SRA could handle BIT_FIELD_REFs just fine - esp. quantities with
a byte size. And then this folding is just premature...
Removing the folding that handles BF != CST fixes it. I know removing
all of it, esp. BF != BF will regress some stuff. I'll put this half-way
patch through testing.
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index 82299bb7f1d..3db383360d6 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -4695,7 +4695,7 @@ optimize_bit_field_compare (location_t loc, enum
tree_code code,
return 0;
if (const_p)
- rreversep = lreversep;
+ return 0;
else
{
/* If this is not a constant, we can only do something if bit positions,
