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 BRIG & HSA parts are a best guess, but seem relatively simple.

2018-05-18  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.

From-SVN: r260348