gcc/ChangeLog.gimple-classes:
	* tree-ssa-forwprop.c (get_prop_dest_stmt): Capture result of
	gimple_assign_ssa_name_copy_p as new local "use_assign", using in
	place of "use_stmt" for typesafety.
	(remove_prop_source_from_use): Add checked cast.
	(rhs_to_tree): Strengthen param "stmt" from gimple to gassign *.
	(forward_propagate_into_comparison): Strengthen local "stmt" from
	gimple to gassign *.
	(forward_propagate_into_cond): Likewise.
	(combine_cond_exprs): Likewise.  Replace local bool "changed" with
	gimple "changed_stmt", adding assignments to "changed_stmt" in
	place of those to "changed".  Replace is_gimple_assign with a
	dyn_cast, using it to strenghten local "def_stmt" from gimple to
	gassign *.
	(tidy_after_forward_propagate_addr): Add checked cast.
	(forward_propagate_addr_expr_1): Strengthen local "use_stmt" from
	gimple to gassign *.
	(forward_propagate_addr_expr): Introduce local "use_assign", using
	it in place of "use_stmt" for typesafety.
	(forward_propagate_comparison): Strengthen local "stmt" from
	gimple to gassign *.  Replace is_gimple_assign with a dyn_cast,
	using it to introduce local "use_assign", using it in place of
	"use_stmt" for typesafety.
	(simplify_conversion_from_bitmask): Strengthen local "stmt" from
	gimple to gassign *.  Replace is_gimple_assign with a dyn_cast,
	using it to introduce local "rhs_def_assign", using it in place of
	"rhs_def_stmt" for typesafety.
	(simplify_not_neg_expr): Strengthen local "stmt" from gimple to
	gassign *.  Replace is_gimple_assign with a dyn_cast,
	using it to strengthen local "rhs_def_stmt" from gimple to
	gassign *.
	(simplify_gimple_switch): Add checked cast.
	(constant_pointer_difference): Replace is_gimple_assign with a
	dyn_cast, using it to strengthen local "stmt" from gimple to
	gassign *.
	(simplify_builtin_call): Capture result of gimple_assign_single_p
	as new local "assign_stmt1", using it in place of "stmt1" for
	typesafety.
	(truth_valued_ssa_name): Add checked cast.
	(lookup_logical_inverted_value): Replace is_gimple_assign with a
	dyn_cast, using it to strengthen local "def" from gimple to
	gassign *.
	(simplify_bitwise_binary_boolean): Likewise for local
	"op0_def_stmt".  Strengthen local "stmt" from gimple to gassign *.
	(simplify_bitwise_binary):  Strengthen local "stmt" from gimple to
	gassign *.
	(simplify_rotate): Likewise.
	(associate_pointerplus_align): Likewise, also for local "def_stmt"
	via various is_gimple_assign becoming dyn_casts.
	(associate_pointerplus_diff): Likewise, also for local "minus".
	(combine_conversions): Likewise.
	(simplify_vce): Likewise.
	(simplify_bitfield_ref): Likewise.
	(simplify_permutation): Likewise.
	(simplify_vector_constructor): Likewise.
	(simplify_mult): Likewise.
	(fold_all_stmts): Capture result of gimple_assign_single_p as new
	local "assign_stmt", using it in place of "stmt" for typesafety.
	(pass_forwprop::execute): Within case GIMPLE_ASSIGN add new
	local "assign_stmt" and use it in place of "stmt" for typesafety.

gcc/ChangeLog.gimple-classes:
	* tree-outof-ssa.c (ssa_is_replaceable_p): Rename param "stmt" to
	"gs", replacing is_gimple_assign with a dyn_cast, using it to
	reintroduce "stmt" as a gassign * for typesafety.  Remove
	redundant is_gimple_call (stmt) test, since we've already checked
	for a GIMPLE_ASSIGN.

gcc/ChangeLog.gimple-classes:
	* ubsan.c (ubsan_expand_null_ifn): Rename local "stmt" to
	"ubsan_null_call" and strengthen from gimple to gcall *.
	Eliminate local gimple "g" in favor of new locals
	"assign_stmt", "builtin_call", "cond_stmt", "and_stmt".
	(instrument_null):  Strengthen local "stmt" from gimple to
	gassign *.
	(instrument_si_overflow): Likewise.
	(instrument_bool_enum_load): Likewise.  Eliminate local gimple
	"g" in favor of new locals "assign_stmt", "cond_stmt",
	"call_stmt".
	(instrument_nonnull_arg): Strengthen local "stmt" from gimple to
	gcall *.  Eliminate local gimple "g" in favor of new locals
	"assign_stmt", "cond_stmt", "call_stmt".
	(instrument_object_size): Strengthen locals "stmt" and "def_stmt"
	from gimple to gassign *.

gcc/ChangeLog.gimple-classes:
	* tsan.c (is_vptr_store): Add checked cast.
	(instrument_gimple): Replace is_gimple_assign with a dyn_cast,
	introducing local "assign_stmt", using in place of "stmt" for
	typesafety.

gcc/ChangeLog.gimple-classes:
	* asan.c (asan_expand_check_ifn): Eliminate local gimple "g",
	breaking it up into new locals "builtin_call", "stmt1",
	"last_stmt", "stmt2", "cond_stmt", "assign_stmt", "last_assign",
	"assign_and", "len_minus_one", "calc_last_byte", "t_ne_zero",
	"library_call".

Users of get_gimple_for_ssa_name call gimple_assign_ accessors on
the result.

This commit changes the return value of get_gimple_for_ssa_name
from gimple to gassign * and uses that within cfgexpand.c and expr.c
for typesafety.

Rationale:
The "SA.values" bitmap is written to by
  tree-out-of-ssa.c:remove_ssa_form
which gets "values" from find_replaceable_exprs (map).

tree-ssa-ter.c:732:find_replaceable_exprs (var_map map)
gets the bitmap from field "replaceable_expressions" within the
temp_expr_table_p.

Bits in the "replaceable_expressions" bitmap are set by
  tree-ssa-ter.c:mark_replaceable
which is called by
  tree-ssa-ter.c:find_replaceable_in_bb
on "use".

"mark_replaceable" can only be called if "same_root_var" is true, which is
only set if gimple_assign_single_p (def_stmt) holds, which implies that
"def_stmt" is a GIMPLE_ASSIGN.
This in turn implies that SSA_NAME_DEF_STMT (use) is a GIMPLE_ASSIGN.

Hence the only ssa-name-defining stmts that can have their bit set
within SA.values are assignments.

Hence get_gimple_for_ssa_name can only return GIMPLE_ASSIGN statements,
hence we can have it return a gassign *, rather than a plain gimple,
and propagate that type knowledge to its callsites.

gcc/ChangeLog.gimple-classes:
	* tree-outof-ssa.h (get_gimple_for_ssa_name): Strengthen return
	type from gimple to gassign *, adding a checked cast, since the
	only ssa-name-defining statements that TER flags are assignments.

	* cfgexpand.c (expand_call_stmt): Strengthen local "def" from
	gimple to gassign *, removing checked casts.
	(expand_debug_expr): Likewise for local "g".
	(expand_gimple_basic_block): Likewise for local "def".
	* expr.c (get_def_for_expr): Strengthen return type and local
	"def_stmt" from gimple to gassign *.
	(get_def_for_expr_class): Likewise.
	(optimize_bitfield_assignment_op): Likewise for locals "srcstmt"
	and "op0stmt".  Remove redundant is_gimple_assign check.
	(store_field): Strengthen local "nop_def" from gimple to
	gassign *.
	(expand_cond_expr_using_cmove): Likewise for local "srcstmt".
	(expand_expr_real_2): Likewise for locals "def", "def0", "def2".
	(stmt_is_replaceable_p): Add a checked cast.
	(expand_expr_real_1): Introduce local "assign_stmt", using it in
	place of "g" within if clause for typesafety.  Strengthen local
	"def_stmt" from gimple to gassign *.
	(do_store_flag): Likewise for local "srcstmt".

gcc/ChangeLog.gimple-classes:
	* tree-ssa.c (ssa_undefined_value_p): Replace is_gimple_assign
	with a dyn_cast, introducing local gassign * "def_assign" and
	using it in place of "def_stmt" for typesafety.
	(execute_update_addresses_taken): In two places, capture the
	result of gimple_assign_single_p as a local gassign *
	"assign_stmt", using them in place of "stmt" for typesafety.

gcc/ChangeLog.gimple-classes:
	* tree-stdarg.c (va_list_counter_bump): Replace is_gimple_assign
	with a dyn_cast, introducing local gassign * "assign_stmt" and
	using it in place of "stmt" for typesafety.  Tighten the scope of
	"stmt".  Introduce another local "assign_stmt" via an as_a, again
	using it in place of "stmt".
	(check_all_va_list_escapes): Replace is_gimple_assign with a
	dyn_cast, introducing local gassign * "assign_stmt" and using it
	in place of "stmt".
	(pass_stdarg::execute): Likewise.

gcc/ChangeLog.gimple-classes:
	* vtable-verify.c (is_vtable_assignment_stmt): Change return type
	from bool to gassign * so that this can be used as a dynamic
	casting function.  Introduce local gassign * "assign_stmt" once we
	know we have a GIMPLE_ASSIGN.  Update return statements
	appropriately.
	(var_is_used_for_virtual_call_p): Replace is_gimple_assign with a
	dyn_cast, using it to introduce local gassign * "assign_stmt2",
	using it in place of "stmt2" for typesafety.
	(verify_bb_vtables): Capture result of is_vtable_assignment_stmt
	as new local gassign * "assign_stmt", using it in place of "stmt"
	for typesafety.

gcc/ChangeLog.gimple-classes:
	* value-prof.c (gimple_divmod_values_to_profile): Rename gimple
	param "stmt" to "gs", reintroducing "stmt" as a local gassign * by
	replacing a check against GIMPLE_ASSIGN with a dyn_cast.