https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110935
Bug ID: 110935
Summary: Missed BB reduction vectorization because of missed
eliding of a permute
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
Target Milestone: ---
double vals[16];
double test ()
{
vals[0]++;
return vals[2] + vals[4] + vals[1] + vals[3];
}
has the reduction not vectorized with -ffast-math because
t.c:5:38: note: === vect_slp_analyze_operations ===
t.c:5:38: note: ==> examining statement: _8 = vals[3];
t.c:5:38: missed: BB vectorization with gaps at the end of a load is not
supported
t.c:5:44: missed: not vectorized: relevant stmt not supported: _8 = vals[3];
t.c:5:38: note: removing SLP instance operations starting from: _11 = _7 +
_8;
t.c:5:38: missed: not vectorized: bad operation in basic block.
we fail to elide the load permutation (BB vect allows a consecutive
sub-set):
t.c:5:38: note: Final SLP tree for instance 0x51c8d60:
t.c:5:38: note: node 0x5285860 (max_nunits=2, refcnt=2) vector(2) double
t.c:5:38: note: op template: _8 = vals[3];
t.c:5:38: note: stmt 0 _8 = vals[3];
t.c:5:38: note: stmt 1 _6 = vals[1];
t.c:5:38: note: stmt 2 _3 = vals[2];
t.c:5:38: note: stmt 3 _4 = vals[4];
t.c:5:38: note: load permutation { 3 1 2 4 }
t.c:5:38: note: === vect_match_slp_patterns ===
t.c:5:38: note: Analyzing SLP tree 0x5285860 for patterns
t.c:5:38: note: SLP optimize permutations:
t.c:5:38: note: 1: { 2, 0, 1, 3 }
t.c:5:38: note: SLP optimize partitions:
t.c:5:38: note: -------------
t.c:5:38: note: partition 0 (layout 0):
t.c:5:38: note: nodes:
t.c:5:38: note: - 0x5285860:
t.c:5:38: note: weight: 1.000000
t.c:5:38: note: op template: _8 = vals[3];
t.c:5:38: note: edges:
t.c:5:38: note: layout 0: (*)
t.c:5:38: note: {depth: 0.000000, total: 0.000000}
t.c:5:38: note: + {depth: 1.000000, total: 1.000000}
t.c:5:38: note: + {depth: 0.000000, total: 0.000000}
t.c:5:38: note: = {depth: 1.000000, total: 1.000000}
t.c:5:38: note: layout 1:
t.c:5:38: note: {depth: 0.000000, total: 0.000000}
t.c:5:38: note: + {depth: 1.000000, total: 1.000000}
t.c:5:38: note: + {depth: 0.000000, total: 0.000000}
t.c:5:38: note: = {depth: 1.000000, total: 1.000000}
t.c:5:38: note: recording new base alignment for &vals
alignment: 32
misalignment: 0
based on: _1 = vals[0];
t.c:5:38: note: === vect_slp_analyze_instance_alignment ===
