Re: Replace FMA_EXPR with one internal fn per optab

[Martin Jambor <mjambor at suse dot cz>]

Hi,

On Fri, May 11 2018, Richard Sandiford wrote:
> There are four optabs for various forms of fused multiply-add:
> fma, fms, fnma and fnms.  Of these, only fma had a direct gimple
> representation.  For the other three we relied on special pattern-
> matching during expand, although tree-ssa-math-opts.c did have
> some code to try to second-guess what expand would do.
>
> This patch removes the old FMA_EXPR representation of fma and
> introduces four new internal functions, one for each optab.
> IFN_FMA is tied to BUILT_IN_FMA* while the other three are
> independent directly-mapped internal functions.  It's then
> possible to do the pattern-matching in match.pd and
> tree-ssa-math-opts.c (via folding) can select the exact
> FMA-based operation.
>
> The patch removes the gimple FE support for __FMA rather than mapping
> it to the internal function.  There's no reason now to treat it
> differently from other internal functions (although the FE doesn't
> handle those yet).
>
> The BRIG & HSA parts are a best guess, but seem relatively simple.

Both parts are OK.

Thanks,

Martin


>
> The genmatch.c changes are structured to allow ternary ops in which
> the second two rather than the first two operands are commutative.
> A later patch makes use of this.
>
> Tested on aarch64-linux-gnu (with and without SVE), aarch64_be-elf,
> x86_64-linux-gnu and powerpc64le-linux-gnu.  OK to install?
>
> Richard
>
>
> 2018-05-11  Richard Sandiford  <richard.sandiford@linaro.org>
>
> gcc/
> 	* doc/sourcebuild.texi (all_scalar_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.
> 	* tree-ssa-math-opts.c (aggressive_valueize): New function.
> 	(convert_mult_to_fma_1): Use the gimple_build interface and use
> 	aggerssive_valueize 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_all_scalar_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: Remove.
> 	* 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.
>