https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87288
--- Comment #6 from bin cheng <amker at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #5)
> it's set here:
>
> if (!is_gimple_val (niters_vector))
> {
> var = create_tmp_var (type, "bnd");
> gimple_seq stmts = NULL;
> niters_vector = force_gimple_operand (niters_vector, &stmts, true,
> var);
> gsi_insert_seq_on_edge_immediate (pe, stmts);
> /* Peeling algorithm guarantees that vector loop bound is at least ONE,
> we set range information to make niters analyzer's life easier. */
> if (stmts != NULL && log_vf)
> set_range_info (niters_vector, VR_RANGE,
> wi::to_wide (build_int_cst (type, 1)),
> wi::to_wide (fold_build2 (RSHIFT_EXPR, type,
> TYPE_MAX_VALUE (type),
> log_vf)));
>
> and the loop is
>
> <bb 5> [local count: 105119325]:
> niters.0_25 = (unsigned int) n_15;
> ni_gap.1_36 = niters.0_25 + 4294967295;
> # RANGE [1, 2147483647] NONZERO 2147483647
> bnd.2_37 = ni_gap.1_36 >> 1;
>
> <bb 4> [local count: 567644349]:
> # ivtmp_50 = PHI <ivtmp_51(6), 0(5)>
> ivtmp_51 = ivtmp_50 + 1;
> if (ivtmp_51 >= bnd.2_37)
> goto <bb 12>; [16.67%]
> else
> goto <bb 6>; [83.33%]
>
> <bb 6> [local count: 473036958]:
> goto <bb 4>; [100.00%]
>
> which looks good according to the comment. So the number of iterations
> _is_ bnd.2_37 - 1 (that number may be zero).
Not really. The code was added under assumption that vector code is guarded by
condition in peeling.
Dump for vect is like:
<bb 2> [local count: 161061274]:
# PT = { D.2425 } (escaped, escaped heap)
# USE = nonlocal null { D.2425 } (escaped, escaped heap)
# CLB = nonlocal null { D.2425 } (escaped, escaped heap)
_10 = operator new [] (32);
_10->_M_elems0 = 0.0;
MEM[(struct array2 *)_10 + 16B]._M_elems0 = 0.0;
# RANGE [-2147483648, 2147483647] NONZERO 4294967294
n_14 = argc_13(D) * 2;
if (n_14 <= 0)
goto <bb 3>; [15.00%]
else
goto <bb 5>; [85.00%]
<bb 3> [local count: 161061274]:
# USE = nonlocal null { D.2425 } (escaped, escaped heap)
# CLB = nonlocal null { D.2425 } (escaped, escaped heap)
operator delete [] (_10);
jacobianTransposeds ={v} {CLOBBER};
return 0;
<bb 5> [local count: 136902083]:
niters.0_25 = (unsigned int) n_14;
ni_gap.1_36 = niters.0_25 + 4294967295;
# RANGE [1, 2147483647] NONZERO 2147483647
bnd.2_37 = ni_gap.1_36 >> 1;
<bb 4> [local count: 739271244]:
# RANGE [0, 2147483647] NONZERO 2147483647
# i_21 = PHI <i_16(6), 0(5)>
# PT = null { D.2425 } (escaped, escaped heap)
# ALIGN = 8, MISALIGN = 0
# vectp.5_40 = PHI <vectp.5_41(6), _10(5)>
# PT = { D.2388 }
# ALIGN = 16, MISALIGN = 0
# vectp_jacobianTransposeds.9_47 = PHI <vectp_jacobianTransposeds.9_48(6),
&jacobianTransposeds(5)>
# ivtmp_50 = PHI <ivtmp_51(6), 0(5)>
# RANGE [0, 2147483646] NONZERO 2147483647
_1 = (long unsigned int) i_21;
# RANGE [0, 34359738336] NONZERO 34359738352
_2 = _1 * 16;
# PT = null { D.2425 } (escaped, escaped heap)
_3 = _10 + _2;
_6 = _1 * 8;
# PT = { D.2388 }
# ALIGN = 8, MISALIGN = 0
_4 = &jacobianTransposeds + _6;
vect__5.7_42 = MEM[(double *)vectp.5_40];
# PT = null { D.2425 } (escaped, escaped heap)
# ALIGN = 8, MISALIGN = 0
vectp.5_43 = vectp.5_40 + 16;
vect__5.8_44 = MEM[(double *)vectp.5_43];
vect_perm_even_45 = VEC_PERM_EXPR <vect__5.7_42, vect__5.8_44, { 0, 2 }>;
vect_perm_odd_46 = VEC_PERM_EXPR <vect__5.7_42, vect__5.8_44, { 1, 3 }>;
_5 = _3->_M_elems0;
MEM[(double &)vectp_jacobianTransposeds.9_47] = vect_perm_even_45;
# RANGE [1, 2147483647] NONZERO 2147483647
i_16 = i_21 + 1;
# PT = null { D.2425 } (escaped, escaped heap)
vectp.5_41 = vectp.5_43 + 16;
# PT = { D.2388 }
# ALIGN = 16, MISALIGN = 0
vectp_jacobianTransposeds.9_48 = vectp_jacobianTransposeds.9_47 + 16;
ivtmp_51 = ivtmp_50 + 1;
if (ivtmp_51 >= bnd.2_37)
goto <bb 12>; [16.67%]
else
goto <bb 6>; [83.33%]
<bb 9> [local count: 136902081]:
goto <bb 3>; [100.00%]
<bb 6> [local count: 616059372]:
goto <bb 4>; [100.00%]
<bb 12> [local count: 136902083]:
niters_vector_mult_vf.3_38 = bnd.2_37 << 1;
tmp.4_39 = (int) niters_vector_mult_vf.3_38;
<bb 13> [local count: 912680552]:
# RANGE [0, 2147483647] NONZERO 2147483647
# i_24 = PHI <i_29(14), tmp.4_39(12)>
# RANGE [0, 2147483646] NONZERO 2147483647
_19 = (long unsigned int) i_24;
# RANGE [0, 34359738336] NONZERO 34359738352
_33 = _19 * 16;
# PT = null { D.2425 } (escaped, escaped heap)
_26 = _10 + _33;
_27 = _19 * 8;
# PT = { D.2388 }
# ALIGN = 8, MISALIGN = 0
_28 = &jacobianTransposeds + _27;
_31 = _26->_M_elems0;
MEM[(double &)_28] = _31;
# RANGE [1, 2147483647] NONZERO 2147483647
i_29 = i_24 + 1;
if (n_14 <= i_29)
goto <bb 9>; [15.00%]
else
goto <bb 14>; [85.00%]
<bb 14> [local count: 775778470]:
goto <bb 13>; [100.00%]
This is no peeling guard condition skipping vector loop anymore. In case of
"argc_13(D) == 1", the vector loop body is executed exactly once (corresponding
2 times before vectorization); after vector loop, the epilog loop body is
executed 2 times again (for the same iteration as done in vector loop). There
is two problems here:
A) it's at least inefficient when ("argc_13(D) == 1" && !SVE).
B) Given the vector loop is not guarded by peeling condition anymore, range
info as you noted should not be set for bnd.2_37, because it could take value
ZERO.
Change in peeling is made by revision 256635, specifically, by below code
changes:
+ poly_uint64 bound_epilog = 0;
+ if (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)
+ && LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo))
+ bound_epilog += vf - 1;
+ if (LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo))
+ bound_epilog += 1;
//......
@@ -2577,10 +2593,8 @@ vect_do_peeling (loop_vec_info loop_vinfo, tree niters,
tree nitersm1,
if (skip_vector)
{
/* Additional epilogue iteration is peeled if gap exists. */
- bool peel_for_gaps = LOOP_VINFO_PEELING_FOR_GAPS (loop_vinfo);
tree t = vect_gen_scalar_loop_niters (niters_prolog, prolog_peeling,
- bound_prolog,
- peel_for_gaps ? vf : vf - 1,
+ bound_prolog, bound_epilog,
Now bound_epilog == 1 is passed into vect_gen_scalar_loop_niters, rather than
vf (== 2), this causes no peeling condition is generated.
Either below condition is too strict here or we need to identify and skip
setting range info in this case:
+ if (!LOOP_VINFO_FULLY_MASKED_P (loop_vinfo)
+ && LOOP_VINFO_PEELING_FOR_NITER (loop_vinfo))
+ bound_epilog += vf - 1;
Thanks
