On Wed, Jul 26, 2023 at 11:14 AM Richard Sandiford <richard.sandif...@arm.com> wrote: > > Richard Biener <richard.guent...@gmail.com> writes: > > On Wed, Jul 26, 2023 at 4:02 AM Hao Liu OS via Gcc-patches > > <gcc-patches@gcc.gnu.org> wrote: > >> > >> > When was STMT_VINFO_REDUC_DEF empty? I just want to make sure that > >> > we're not papering over an issue elsewhere. > >> > >> Yes, I also wonder if this is an issue in vectorizable_reduction. Below > >> is the the gimple of "gcc.target/aarch64/sve/cost_model_13.c": > >> > >> <bb 3>: > >> # res_18 = PHI <res_15(7), 0(6)> > >> # i_20 = PHI <i_16(7), 0(6)> > >> _1 = (long unsigned int) i_20; > >> _2 = _1 * 2; > >> _3 = x_14(D) + _2; > >> _4 = *_3; > >> _5 = (unsigned short) _4; > >> res.0_6 = (unsigned short) res_18; > >> _7 = _5 + res.0_6; <-- The current stmt_info > >> res_15 = (short int) _7; > >> i_16 = i_20 + 1; > >> if (n_11(D) > i_16) > >> goto <bb 7>; > >> else > >> goto <bb 4>; > >> > >> <bb 7>: > >> goto <bb 3>; > >> > >> It looks like that STMT_VINFO_REDUC_DEF should be "res_18 = PHI > >> <res_15(7), 0(6)>"? > >> The status here is: > >> STMT_VINFO_REDUC_IDX (stmt_info): 1 > >> STMT_VINFO_REDUC_TYPE (stmt_info): TREE_CODE_REDUCTION > >> STMT_VINFO_REDUC_VECTYPE (stmt_info): 0x0 > > > > Not all stmts in the SSA cycle forming the reduction have > > STMT_VINFO_REDUC_DEF set, > > only the last (latch def) and live stmts have at the moment. > > Ah, thanks. In that case, Hao, I think we can avoid the ICE by changing: > > if ((kind == scalar_stmt || kind == vector_stmt || kind == vec_to_scalar) > && vect_is_reduction (stmt_info)) > > to: > > if ((kind == scalar_stmt || kind == vector_stmt || kind == vec_to_scalar) > && STMT_VINFO_LIVE_P (stmt_info) > && vect_is_reduction (stmt_info)) > > instead of using a null check.
But as seen you will miss stmts that are part of the reduction then? In principle we could put STMT_VINFO_REDUC_DEF to other stmts as well. See vectorizable_reduction in the while (reduc_def != PHI_RESULT (reduc_def_phi)) loop. > I see that vectorizable_reduction calculates a reduc_chain_length. > Would it be OK to store that in the stmt_vec_info? I suppose the > AArch64 code should be multiplying by that as well. (It would be a > separate patch from this one though.) I don't think that's too relevant here (it also counts noop conversions). Richard. > > Richard > > > > > > Richard. > > > >> Thanks, > >> Hao > >> > >> ________________________________________ > >> From: Richard Sandiford <richard.sandif...@arm.com> > >> Sent: Tuesday, July 25, 2023 17:44 > >> To: Hao Liu OS > >> Cc: GCC-patches@gcc.gnu.org > >> Subject: Re: [PATCH] AArch64: Do not increase the vect reduction latency > >> by multiplying count [PR110625] > >> > >> Hao Liu OS <h...@os.amperecomputing.com> writes: > >> > Hi, > >> > > >> > Thanks for the suggestion. I tested it and found a gcc_assert failure: > >> > gcc.target/aarch64/sve/cost_model_13.c (internal compiler error: in > >> > info_for_reduction, at tree-vect-loop.cc:5473) > >> > > >> > It is caused by empty STMT_VINFO_REDUC_DEF. > >> > >> When was STMT_VINFO_REDUC_DEF empty? I just want to make sure that > >> we're not papering over an issue elsewhere. > >> > >> Thanks, > >> Richard > >> > >> So, I added an extra check before checking single_defuse_cycle. The > >> updated patch is below. Is it OK for trunk? > >> > > >> > --- > >> > > >> > The new costs should only count reduction latency by multiplying count > >> > for > >> > single_defuse_cycle. For other situations, this will increase the > >> > reduction > >> > latency a lot and miss vectorization opportunities. > >> > > >> > Tested on aarch64-linux-gnu. > >> > > >> > gcc/ChangeLog: > >> > > >> > PR target/110625 > >> > * config/aarch64/aarch64.cc (count_ops): Only '* count' for > >> > single_defuse_cycle while counting reduction_latency. > >> > > >> > gcc/testsuite/ChangeLog: > >> > > >> > * gcc.target/aarch64/pr110625_1.c: New testcase. > >> > * gcc.target/aarch64/pr110625_2.c: New testcase. > >> > --- > >> > gcc/config/aarch64/aarch64.cc | 13 ++++-- > >> > gcc/testsuite/gcc.target/aarch64/pr110625_1.c | 46 +++++++++++++++++++ > >> > gcc/testsuite/gcc.target/aarch64/pr110625_2.c | 14 ++++++ > >> > 3 files changed, 69 insertions(+), 4 deletions(-) > >> > create mode 100644 gcc/testsuite/gcc.target/aarch64/pr110625_1.c > >> > create mode 100644 gcc/testsuite/gcc.target/aarch64/pr110625_2.c > >> > > >> > diff --git a/gcc/config/aarch64/aarch64.cc > >> > b/gcc/config/aarch64/aarch64.cc > >> > index 560e5431636..478a4e00110 100644 > >> > --- a/gcc/config/aarch64/aarch64.cc > >> > +++ b/gcc/config/aarch64/aarch64.cc > >> > @@ -16788,10 +16788,15 @@ aarch64_vector_costs::count_ops (unsigned int > >> > count, vect_cost_for_stmt kind, > >> > { > >> > unsigned int base > >> > = aarch64_in_loop_reduction_latency (m_vinfo, stmt_info, > >> > m_vec_flags); > >> > - > >> > - /* ??? Ideally we'd do COUNT reductions in parallel, but > >> > unfortunately > >> > - that's not yet the case. */ > >> > - ops->reduction_latency = MAX (ops->reduction_latency, base * > >> > count); > >> > + if (STMT_VINFO_REDUC_DEF (stmt_info) > >> > + && STMT_VINFO_FORCE_SINGLE_CYCLE ( > >> > + info_for_reduction (m_vinfo, stmt_info))) > >> > + /* ??? Ideally we'd use a tree to reduce the copies down to 1 > >> > vector, > >> > + and then accumulate that, but at the moment the loop-carried > >> > + dependency includes all copies. */ > >> > + ops->reduction_latency = MAX (ops->reduction_latency, base * > >> > count); > >> > + else > >> > + ops->reduction_latency = MAX (ops->reduction_latency, base); > >> > } > >> > > >> > /* Assume that multiply-adds will become a single operation. */ > >> > diff --git a/gcc/testsuite/gcc.target/aarch64/pr110625_1.c > >> > b/gcc/testsuite/gcc.target/aarch64/pr110625_1.c > >> > new file mode 100644 > >> > index 00000000000..0965cac33a0 > >> > --- /dev/null > >> > +++ b/gcc/testsuite/gcc.target/aarch64/pr110625_1.c > >> > @@ -0,0 +1,46 @@ > >> > +/* { dg-do compile } */ > >> > +/* { dg-options "-Ofast -mcpu=neoverse-n2 -fdump-tree-vect-details > >> > -fno-tree-slp-vectorize" } */ > >> > +/* { dg-final { scan-tree-dump-not "reduction latency = 8" "vect" } } */ > >> > + > >> > +/* Do not increase the vector body cost due to the incorrect reduction > >> > latency > >> > + Original vector body cost = 51 > >> > + Scalar issue estimate: > >> > + ... > >> > + reduction latency = 2 > >> > + estimated min cycles per iteration = 2.000000 > >> > + estimated cycles per vector iteration (for VF 2) = 4.000000 > >> > + Vector issue estimate: > >> > + ... > >> > + reduction latency = 8 <-- Too large > >> > + estimated min cycles per iteration = 8.000000 > >> > + Increasing body cost to 102 because scalar code would issue more > >> > quickly > >> > + ... > >> > + missed: cost model: the vector iteration cost = 102 divided by the > >> > scalar iteration cost = 44 is greater or equal to the vectorization > >> > factor = 2. > >> > + missed: not vectorized: vectorization not profitable. */ > >> > + > >> > +typedef struct > >> > +{ > >> > + unsigned short m1, m2, m3, m4; > >> > +} the_struct_t; > >> > +typedef struct > >> > +{ > >> > + double m1, m2, m3, m4, m5; > >> > +} the_struct2_t; > >> > + > >> > +double > >> > +bar (the_struct2_t *); > >> > + > >> > +double > >> > +foo (double *k, unsigned int n, the_struct_t *the_struct) > >> > +{ > >> > + unsigned int u; > >> > + the_struct2_t result; > >> > + for (u = 0; u < n; u++, k--) > >> > + { > >> > + result.m1 += (*k) * the_struct[u].m1; > >> > + result.m2 += (*k) * the_struct[u].m2; > >> > + result.m3 += (*k) * the_struct[u].m3; > >> > + result.m4 += (*k) * the_struct[u].m4; > >> > + } > >> > + return bar (&result); > >> > +} > >> > diff --git a/gcc/testsuite/gcc.target/aarch64/pr110625_2.c > >> > b/gcc/testsuite/gcc.target/aarch64/pr110625_2.c > >> > new file mode 100644 > >> > index 00000000000..7a84aa8355e > >> > --- /dev/null > >> > +++ b/gcc/testsuite/gcc.target/aarch64/pr110625_2.c > >> > @@ -0,0 +1,14 @@ > >> > +/* { dg-do compile } */ > >> > +/* { dg-options "-Ofast -mcpu=neoverse-n2 -fdump-tree-vect-details > >> > -fno-tree-slp-vectorize" } */ > >> > +/* { dg-final { scan-tree-dump "reduction latency = 8" "vect" } } */ > >> > + > >> > +/* The reduction latency should be multiplied by the count for > >> > + single_defuse_cycle. */ > >> > + > >> > +long > >> > +f (long res, short *ptr1, short *ptr2, int n) > >> > +{ > >> > + for (int i = 0; i < n; ++i) > >> > + res += (long) ptr1[i] << ptr2[i]; > >> > + return res; > >> > +}