Replace FMA_EXPR with one internal fn per optab
H.J. Lu
hjl.tools@gmail.com
Tue May 22 20:11:00 GMT 2018
On Thu, May 17, 2018 at 1:56 AM, Richard Sandiford
<richard.sandiford@linaro.org> wrote:
> Richard Biener <richard.guenther@gmail.com> writes:
>>> @@ -2698,23 +2703,26 @@ convert_mult_to_fma_1 (tree mul_result,
>>> }
>>
>>> if (negate_p)
>>> - mulop1 = force_gimple_operand_gsi (&gsi,
>>> - build1 (NEGATE_EXPR,
>>> - type, mulop1),
>>> - true, NULL_TREE, true,
>>> - GSI_SAME_STMT);
>>> + mulop1 = gimple_build (&seq, NEGATE_EXPR, type, mulop1);
>>
>>> - fma_stmt = gimple_build_assign (gimple_assign_lhs (use_stmt),
>>> - FMA_EXPR, mulop1, op2, addop);
>>> + if (seq)
>>> + gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
>>> + fma_stmt = gimple_build_call_internal (IFN_FMA, 3, mulop1, op2,
>> addop);
>>> + gimple_call_set_lhs (fma_stmt, gimple_assign_lhs (use_stmt));
>>> + gimple_call_set_nothrow (fma_stmt, !stmt_can_throw_internal
>> (use_stmt));
>>> + gsi_replace (&gsi, fma_stmt, true);
>>> + /* Valueize aggressively so that we generate FMS, FNMA and FNMS
>>> + regardless of where the negation occurs. */
>>> + if (fold_stmt (&gsi, aggressive_valueize))
>>> + update_stmt (gsi_stmt (gsi));
>>
>> I think it would be nice to be able to use gimple_build () with IFNs so you
>> can
>> gimple_build () the IFN and then use gsi_replace_with_seq () on it. You
>> only need to fold with generated negates, not with negates already in the
>> IL?
>> The the folding implied with gimple_build will take care of it.
>
> The idea was to pick up existing negates that feed the multiplication
> as well as any added by the pass itself.
>
> On IRC yesterday we talked about how this should handle the ECF_NOTHROW
> flag, and whether things like IFN_SQRT and IFN_FMA should always be
> nothrow (like the built-in functions are). But in the end I thought
> it'd be better to keep things as they are. We already handle
> -fnon-call-exceptions for unfused a * b + c and before the patch also
> handled it for FMA_EXPR. It'd seem like a step backwards if the new
> internal functions didn't handle it too. If anything it seems like the
> built-in functions should change to be closer to the tree_code and
> internal_fn way of doing things, if we want to support -fnon-call-exceptions
> properly.
>
> This also surprised me when doing the if-conversion patch I sent yesterday.
> We're happy to vectorise:
>
> for (int i = 0; i < 100; ++i)
> x[i] = ... ? sqrt (x[i]) : 0;
>
> by doing the sqrt unconditionally and selecting on the result, even with
> the default maths flags, but refuse to vectorise the simpler:
>
> for (int i = 0; i < 100; ++i)
> x[i] = ... ? x[i] + 1 : 0;
>
> in the same way.
>
>> Otherwise can you please move aggressive_valueize to gimple-fold.[ch]
>> alongside no_follow_ssa_edges / follow_single_use_edges and maybe
>> rename it as follow_all_ssa_edges?
>
> Ah, yeah, that's definitely a better name.
>
> I also renamed all_scalar_fma to scalar_all_fma, since I realised
> after Andrew's reply that the old name made it sound like it was
> "all scalars", whereas it meant to mean "all fmas".
>
> Tested as before.
>
> Thanks,
> Richard
>
> 2018-05-17 Richard Sandiford <richard.sandiford@linaro.org>
>
> gcc/
> * doc/sourcebuild.texi (scalar_all_fma): Document.
> * tree.def (FMA_EXPR): Delete.
> * internal-fn.def (FMA, FMS, FNMA, FNMS): New internal functions.
> * internal-fn.c (ternary_direct): New macro.
> (expand_ternary_optab_fn): Likewise.
> (direct_ternary_optab_supported_p): Likewise.
> * Makefile.in (build/genmatch.o): Depend on case-fn-macros.h.
> * builtins.c (fold_builtin_fma): Delete.
> (fold_builtin_3): Don't call it.
> * cfgexpand.c (expand_debug_expr): Remove FMA_EXPR handling.
> * expr.c (expand_expr_real_2): Likewise.
> * fold-const.c (operand_equal_p): Likewise.
> (fold_ternary_loc): Likewise.
> * gimple-pretty-print.c (dump_ternary_rhs): Likewise.
> * gimple.c (DEFTREECODE): Likewise.
> * gimplify.c (gimplify_expr): Likewise.
> * optabs-tree.c (optab_for_tree_code): Likewise.
> * tree-cfg.c (verify_gimple_assign_ternary): Likewise.
> * tree-eh.c (operation_could_trap_p): Likewise.
> (stmt_could_throw_1_p): Likewise.
> * tree-inline.c (estimate_operator_cost): Likewise.
> * tree-pretty-print.c (dump_generic_node): Likewise.
> (op_code_prio): Likewise.
> * tree-ssa-loop-im.c (stmt_cost): Likewise.
> * tree-ssa-operands.c (get_expr_operands): Likewise.
> * tree.c (commutative_ternary_tree_code, add_expr): Likewise.
> * fold-const-call.h (fold_fma): Delete.
> * fold-const-call.c (fold_const_call_ssss): Handle CFN_FMS,
> CFN_FNMA and CFN_FNMS.
> (fold_fma): Delete.
> * genmatch.c (combined_fn): New enum.
> (commutative_ternary_tree_code): Remove FMA_EXPR handling.
> (commutative_op): New function.
> (commutate): Use it. Handle more than 2 operands.
> (dt_operand::gen_gimple_expr): Use commutative_op.
> (parser::parse_expr): Allow :c to be used with non-binary
> operators if the commutative operand is known.
> * gimple-ssa-backprop.c (backprop::process_builtin_call_use): Handle
> CFN_FMS, CFN_FNMA and CFN_FNMS.
> (backprop::process_assign_use): Remove FMA_EXPR handling.
> * hsa-gen.c (gen_hsa_insns_for_operation_assignment): Likewise.
> (gen_hsa_fma): New function.
> (gen_hsa_insn_for_internal_fn_call): Use it for IFN_FMA, IFN_FMS,
> IFN_FNMA and IFN_FNMS.
> * match.pd: Add folds for IFN_FMS, IFN_FNMA and IFN_FNMS.
> * gimple-fold.h (follow_all_ssa_edges): Declare.
> * gimple-fold.c (follow_all_ssa_edges): New function.
> * tree-ssa-math-opts.c (convert_mult_to_fma_1): Use the
> gimple_build interface and use follow_all_ssa_edges to fold the result.
> (convert_mult_to_fma): Use direct_internal_fn_suppoerted_p
> instead of checking for optabs directly.
> * config/i386/i386.c (ix86_add_stmt_cost): Recognize FMAs as calls
> rather than FMA_EXPRs.
> * config/rs6000/rs6000.c (rs6000_gimple_fold_builtin): Create a
> call to IFN_FMA instead of an FMA_EXPR.
>
> gcc/brig/
> * brigfrontend/brig-function.cc
> (brig_function::get_builtin_for_hsa_opcode): Use BUILT_IN_FMA
> for BRIG_OPCODE_FMA.
> (brig_function::get_tree_code_for_hsa_opcode): Treat BUILT_IN_FMA
> as a call.
>
> gcc/c/
> * gimple-parser.c (c_parser_gimple_postfix_expression): Remove
> __FMA_EXPR handlng.
>
> gcc/cp/
> * constexpr.c (cxx_eval_constant_expression): Remove FMA_EXPR handling.
> (potential_constant_expression_1): Likewise.
>
> gcc/testsuite/
> * lib/target-supports.exp (check_effective_target_scalar_all_fma):
> New proc.
> * gcc.dg/fma-1.c: New test.
> * gcc.dg/fma-2.c: Likewise.
> * gcc.dg/fma-3.c: Likewise.
> * gcc.dg/fma-4.c: Likewise.
> * gcc.dg/fma-5.c: Likewise.
> * gcc.dg/fma-6.c: Likewise.
> * gcc.dg/fma-7.c: Likewise.
> * gcc.dg/gimplefe-26.c: Use .FMA instead of __FMA and require
> scalar_all_fma.
> * gfortran.dg/reassoc_7.f: Pass -ffp-contract=off.
> * gfortran.dg/reassoc_8.f: Likewise.
> * gfortran.dg/reassoc_9.f: Likewise.
> * gfortran.dg/reassoc_10.f: Likewise.
>
This caused:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85881
H.J.
More information about the Gcc-patches
mailing list