@section Flags in an RTL Expression
@cindex flags in RTL expression
-RTL expressions contain several flags (one-bit bit-fields) and other
-values that are used in certain types of expression. Most often they
-are accessed with the following macros:
+RTL expressions contain several flags (one-bit bit-fields)
+that are used in certain types of expression. Most often they
+are accessed with the following macros, which expand into lvalues:
@table @code
-@findex MEM_VOLATILE_P
-@cindex @code{mem} and @samp{/v}
-@cindex @code{volatil}, in @code{mem}
-@cindex @samp{/v} in RTL dump
-@item MEM_VOLATILE_P (@var{x})
-In @code{mem} expressions, nonzero for volatile memory references.
+@findex CONSTANT_POOL_ADDRESS_P
+@cindex @code{symbol_ref} and @samp{/u}
+@cindex @code{unchanging}, in @code{symbol_ref}
+@item CONSTANT_POOL_ADDRESS_P (@var{x})
+Nonzero in a @code{symbol_ref} if it refers to part of the current
+function's constant pool. For most targets these addresses are in a
+@code{.rodata} section entirely separate from the function, but for
+some targets the addresses are close to the beginning of the function.
+In either case GCC assumes these addresses can be addressed directly,
+perhaps with the help of base registers.
+Stored in the @code{unchanging} field and printed as @samp{/u}.
+
+@findex CONST_OR_PURE_CALL_P
+@cindex @code{call_insn} and @samp{/u}
+@cindex @code{unchanging}, in @code{call_insn}
+@item CONST_OR_PURE_CALL_P (@var{x})
+In a @code{call_insn}, @code{note}, or an @code{expr_list} for notes,
+indicates that the insn represents a call to a const or pure function.
+Stored in the @code{unchanging} field and printed as @samp{/u}.
+
+@findex INSN_ANNULLED_BRANCH_P
+@cindex @code{insn} and @samp{/u}
+@cindex @code{unchanging}, in @code{insn}
+@item INSN_ANNULLED_BRANCH_P (@var{x})
+In an @code{insn} in the delay slot of a branch insn, indicates that an
+annulling branch should be used. See the discussion under
+@code{sequence} below. Stored in the @code{unchanging} field and printed
+as @samp{/u}.
+
+@findex INSN_DEAD_CODE_P
+@cindex @code{insn} and @samp{/s}
+@cindex @code{in_struct}, in @code{insn}
+@item INSN_DEAD_CODE_P (@var{x})
+In an @code{insn} during the dead-code elimination pass, nonzero if the
+insn is dead.
+Stored in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex INSN_DELETED_P
+@cindex @code{insn} and @samp{/v}
+@cindex @code{volatil}, in @code{insn}
+@item INSN_DELETED_P (@var{x})
+In an @code{insn}, nonzero if the insn has been deleted. Stored in the
+@code{volatil} field and printed as @samp{/v}.
+
+@findex INSN_FROM_TARGET_P
+@cindex @code{insn} and @samp{/s}
+@cindex @code{in_struct}, in @code{insn}
+@item INSN_FROM_TARGET_P (@var{x})
+In an @code{insn} in a delay slot of a branch, indicates that the insn
+is from the target of the branch. If the branch insn has
+@code{INSN_ANNULLED_BRANCH_P} set, this insn will only be executed if
+the branch is taken. For annulled branches with
+@code{INSN_FROM_TARGET_P} clear, the insn will be executed only if the
+branch is not taken. When @code{INSN_ANNULLED_BRANCH_P} is not set,
+this insn will always be executed. Stored in the @code{in_struct}
+field and printed as @samp{/s}.
+
+@findex LABEL_OUTSIDE_LOOP_P
+@cindex @code{label_ref} and @samp{/s}
+@cindex @code{in_struct}, in @code{label_ref}
+@item LABEL_OUTSIDE_LOOP_P (@var{x})
+In @code{label_ref} expressions, nonzero if this is a reference to a
+label that is outside the innermost loop containing the reference to the
+label. Stored in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex LABEL_PRESERVE_P
+@cindex @code{code_label} and @samp{/i}
+@cindex @code{in_struct}, in @code{code_label}
+@item LABEL_PRESERVE_P (@var{x})
+In a @code{code_label}, indicates that the label is referenced by
+code or data not visible to the RTL of a given function.
+Labels referenced by a non-local goto will have this bit set. Stored
+in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex LABEL_REF_NONLOCAL_P
+@cindex @code{label_ref} and @samp{/v}
+@cindex @code{volatil}, in @code{label_ref}
+@item LABEL_REF_NONLOCAL_P (@var{x})
+In @code{label_ref} and @code{reg_label} expressions, nonzero if this is
+a reference to a non-local label.
Stored in the @code{volatil} field and printed as @samp{/v}.
+@findex LINK_COST_FREE
+@cindex @code{insn_list} and @samp{/c}
+@cindex @code{call}, in @code{insn_list}
+@item LINK_COST_FREE (@var{x})
+In the @code{LOG_LINKS} @code{insn_list} during scheduling, nonzero when
+the cost of executing an instruction through the link is zero, i.e., the
+link makes the cost free. Stored in the @code{call} field and printed
+as @samp{/c}.
+
+@findex LINK_COST_ZERO
+@cindex @code{insn_list} and @samp{/j}
+@cindex @code{jump}, in @code{insn_list}
+@item LINK_COST_ZERO (@var{x})
+In the @code{LOG_LINKS} @code{insn_list} during scheduling, nonzero when
+the cost of executing an instruction through the link varies and is
+unchanged, i.e., the link has zero additional cost.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
@findex MEM_IN_STRUCT_P
@cindex @code{mem} and @samp{/s}
@cindex @code{in_struct}, in @code{mem}
-@cindex @samp{/s} in RTL dump
@item MEM_IN_STRUCT_P (@var{x})
In @code{mem} expressions, nonzero for reference to an entire structure,
union or array, or to a component of one. Zero for references to a
-scalar variable or through a pointer to a scalar. Stored in the
-@code{in_struct} field and printed as @samp{/s}. If both this flag and
-MEM_SCALAR_P are clear, then we don't know whether this MEM is in a
-structure or not. Both flags should never be simultaneously set.
+scalar variable or through a pointer to a scalar. If both this flag and
+@code{MEM_SCALAR_P} are clear, then we don't know whether this @code{mem}
+is in a structure or not. Both flags should never be simultaneously set.
+Stored in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex MEM_KEEP_ALIAS_SET_P
+@cindex @code{mem} and @samp{/j}
+@cindex @code{jump}, in @code{mem}
+@item MEM_KEEP_ALIAS_SET_P (@var{x})
+In @code{mem} expressions, 1 if we should keep the alias set for this
+mem unchanged when we access a component. Set to 1, for example, when we
+are already in a non-addressable component of an aggregate.
+Stored in the @code{jump} field and printed as @samp{/j}.
@findex MEM_SCALAR_P
@cindex @code{mem} and @samp{/f}
-@cindex @code{frame_related}, in@code{mem}
-@cindex @samp{/f} in RTL dump
+@cindex @code{frame_related}, in @code{mem}
@item MEM_SCALAR_P (@var{x})
In @code{mem} expressions, nonzero for reference to a scalar known not
to be a member of a structure, union, or array. Zero for such
references and for indirections through pointers, even pointers pointing
-to scalar types. If both this flag and MEM_STRUCT_P are clear, then we
-don't know whether this MEM is in a structure or not. Both flags should
+to scalar types. If both this flag and @code{MEM_STRUCT_P} are clear, then we
+don't know whether this @code{mem} is in a structure or not. Both flags should
never be simultaneously set.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
-@findex MEM_ALIAS_SET
-@item MEM_ALIAS_SET (@var{x})
-In @code{mem} expressions, the alias set to which @var{x} belongs. If
-zero, @var{x} is not in any alias set, and may alias anything. If
-nonzero, @var{x} may only alias objects in the same alias set. This
-value is set (in a language-specific manner) by the front end. This
-field is not a bit-field; it is in an integer, found as the second
-argument to the @code{mem}.
+@findex MEM_VOLATILE_P
+@cindex @code{mem} and @samp{/v}
+@cindex @code{volatil}, in @code{mem}
+@item MEM_VOLATILE_P (@var{x})
+In @code{mem} and @code{asm_operands} expressions, nonzero for volatile
+memory references.
+Stored in the @code{volatil} field and printed as @samp{/v}.
+
+@findex REG_FUNCTION_VALUE_P
+@cindex @code{reg} and @samp{/i}
+@cindex @code{integrated}, in @code{reg}
+@item REG_FUNCTION_VALUE_P (@var{x})
+Nonzero in a @code{reg} if it is the place in which this function's
+value is going to be returned. (This happens only in a hard
+register.) Stored in the @code{integrated} field and printed as
+@samp{/i}.
@findex REG_LOOP_TEST_P
@cindex @code{reg} and @samp{/s}
@cindex @code{in_struct}, in @code{reg}
-@item REG_LOOP_TEST_P
+@item REG_LOOP_TEST_P (@var{x})
In @code{reg} expressions, nonzero if this register's entire life is
contained in the exit test code for some loop. Stored in the
@code{in_struct} field and printed as @samp{/s}.
+@findex REG_POINTER
+@cindex @code{reg} and @samp{/f}
+@cindex @code{frame_related}, in @code{reg}
+@item REG_POINTER (@var{x})
+Nonzero in a @code{reg} if the register holds a pointer. Stored in the
+@code{frame_related} field and printed as @samp{/f}.
+
@findex REG_USERVAR_P
@cindex @code{reg} and @samp{/v}
@cindex @code{volatil}, in @code{reg}
the compiler. Stored in the @code{volatil} field and printed as
@samp{/v}.
-@cindex @samp{/i} in RTL dump
-@findex REG_FUNCTION_VALUE_P
-@cindex @code{reg} and @samp{/i}
-@cindex @code{integrated}, in @code{reg}
-@item REG_FUNCTION_VALUE_P (@var{x})
-Nonzero in a @code{reg} if it is the place in which this function's
-value is going to be returned. (This happens only in a hard
-register.) Stored in the @code{integrated} field and printed as
-@samp{/i}.
-
The same hard register may be used also for collecting the values of
functions called by this one, but @code{REG_FUNCTION_VALUE_P} is zero
in this kind of use.
-@cindex @samp{/f} in RTL dump
-@findex REG_POINTER
-@cindex @code{reg} and @samp{/f}
-@cindex @code{frame_related}, in @code{reg}
-@item REG_POINTER (@var{x})
-Nonzero in a @code{reg} if the register holds a pointer. Stored in the
-@code{frame_related} field and printed as @samp{/f}.
-
-@findex SUBREG_PROMOTED_VAR_P
-@cindex @code{subreg} and @samp{/s}
-@cindex @code{in_struct}, in @code{subreg}
-@item SUBREG_PROMOTED_VAR_P
-Nonzero in a @code{subreg} if it was made when accessing an object that
-was promoted to a wider mode in accord with the @code{PROMOTED_MODE} machine
-description macro (@pxref{Storage Layout}). In this case, the mode of
-the @code{subreg} is the declared mode of the object and the mode of
-@code{SUBREG_REG} is the mode of the register that holds the object.
-Promoted variables are always either sign- or zero-extended to the wider
-mode on every assignment. Stored in the @code{in_struct} field and
-printed as @samp{/s}.
-
-@findex SUBREG_PROMOTED_UNSIGNED_P
-@cindex @code{subreg} and @samp{/u}
-@cindex @code{unchanging}, in @code{subreg}
-@item SUBREG_PROMOTED_UNSIGNED_P
-Nonzero in a @code{subreg} that has @code{SUBREG_PROMOTED_VAR_P} nonzero
-if the object being referenced is kept zero-extended and zero if it
-is kept sign-extended. Stored in the @code{unchanging} field and
-printed as @samp{/u}.
-
-@findex RTX_UNCHANGING_P
-@cindex @code{reg} and @samp{/u}
-@cindex @code{mem} and @samp{/u}
-@cindex @code{unchanging}, in @code{reg} and @code{mem}
-@cindex @samp{/u} in RTL dump
-@item RTX_UNCHANGING_P (@var{x})
-Nonzero in a @code{reg} or @code{mem} if the value is not changed.
-(This flag is not set for memory references via pointers to constants.
-Such pointers only guarantee that the object will not be changed
-explicitly by the current function. The object might be changed by
-other functions or by aliasing.) Stored in the
-@code{unchanging} field and printed as @samp{/u}.
-
-@findex RTX_INTEGRATED_P
-@cindex @code{integrated}, in @code{insn}
-@item RTX_INTEGRATED_P (@var{insn})
-Nonzero in an insn if it resulted from an in-line function call.
-Stored in the @code{integrated} field and printed as @samp{/i}.
-
@findex RTX_FRAME_RELATED_P
+@cindex @code{insn} and @samp{/f}
+@cindex @code{frame_related}, in @code{insn}
@item RTX_FRAME_RELATED_P (@var{x})
-Nonzero in an insn or expression which is part of a function prologue
+Nonzero in an @code{insn} or @code{set} which is part of a function prologue
and sets the stack pointer, sets the frame pointer, or saves a register.
This flag should also be set on an instruction that sets up a temporary
register to use in place of the frame pointer.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
In particular, on RISC targets where there are limits on the sizes of
immediate constants, it is sometimes impossible to reach the register
This flag is required for exception handling support on targets with RTL
prologues.
-@findex SYMBOL_REF_USED
-@cindex @code{used}, in @code{symbol_ref}
-@item SYMBOL_REF_USED (@var{x})
-In a @code{symbol_ref}, indicates that @var{x} has been used. This is
-normally only used to ensure that @var{x} is only declared external
-once. Stored in the @code{used} field.
+@findex RTX_INTEGRATED_P
+@cindex @code{insn} and @samp{/i}
+@cindex @code{integrated}, in @code{insn}
+@item RTX_INTEGRATED_P (@var{x})
+Nonzero in an @code{insn}, @code{insn_list}, or @code{const} if it
+resulted from an in-line function call.
+Stored in the @code{integrated} field and printed as @samp{/i}.
+
+@findex RTX_UNCHANGING_P
+@cindex @code{reg} and @samp{/u}
+@cindex @code{mem} and @samp{/u}
+@cindex @code{unchanging}, in @code{reg} and @code{mem}
+@item RTX_UNCHANGING_P (@var{x})
+Nonzero in a @code{reg} or @code{mem} if the memory is set at most once,
+anywhere. This does not mean that it is function invariant.
+Stored in the @code{unchanging} field and printed as @samp{/u}.
+
+@findex SCHED_GROUP_P
+@cindex @code{insn} and @samp{/i}
+@cindex @code{in_struct}, in @code{insn}
+@item SCHED_GROUP_P (@var{x})
+During instruction scheduling, in an @code{insn}, indicates that the
+previous insn must be scheduled together with this insn. This is used to
+ensure that certain groups of instructions will not be split up by the
+instruction scheduling pass, for example, @code{use} insns before
+a @code{call_insn} may not be separated from the @code{call_insn}.
+Stored in the @code{in_struct} field and printed as @samp{/s}.
+
+@findex SET_IS_RETURN_P
+@cindex @code{insn} and @samp{/j}
+@cindex @code{jump}, in @code{insn}
+@item SET_IS_RETURN_P (@var{x})
+For a @code{set}, nonzero if it is for a return.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
+@findex SIBLING_CALL_P
+@cindex @code{call_insn} and @samp{/j}
+@cindex @code{jump}, in @code{call_insn}
+@item SIBLING_CALL_P (@var{x})
+For a @code{call_insn}, nonzero if the insn is a sibling call.
+Stored in the @code{jump} field and printed as @samp{/j}.
+
+@findex STRING_POOL_ADDRESS_P
+@cindex @code{symbol_ref} and @samp{/f}
+@cindex @code{frame_related}, in @code{symbol_ref}
+@item STRING_POOL_ADDRESS_P (@var{x})
+For a @code{symbol_ref} expression, nonzero if it addresses this function's
+string constant pool.
+Stored in the @code{frame_related} field and printed as @samp{/f}.
+
+@findex SUBREG_PROMOTED_UNSIGNED_P
+@cindex @code{subreg} and @samp{/u}
+@cindex @code{unchanging}, in @code{subreg}
+@item SUBREG_PROMOTED_UNSIGNED_P (@var{x})
+Nonzero in a @code{subreg} that has @code{SUBREG_PROMOTED_VAR_P} nonzero
+if the object being referenced is kept zero-extended and zero if it
+is kept sign-extended. Stored in the @code{unchanging} field and
+printed as @samp{/u}.
+
+@findex SUBREG_PROMOTED_VAR_P
+@cindex @code{subreg} and @samp{/s}
+@cindex @code{in_struct}, in @code{subreg}
+@item SUBREG_PROMOTED_VAR_P (@var{x})
+Nonzero in a @code{subreg} if it was made when accessing an object that
+was promoted to a wider mode in accord with the @code{PROMOTED_MODE} machine
+description macro (@pxref{Storage Layout}). In this case, the mode of
+the @code{subreg} is the declared mode of the object and the mode of
+@code{SUBREG_REG} is the mode of the register that holds the object.
+Promoted variables are always either sign- or zero-extended to the wider
+mode on every assignment. Stored in the @code{in_struct} field and
+printed as @samp{/s}.
@findex SYMBOL_REF_FLAG
@cindex @code{symbol_ref} and @samp{/v}
In a @code{symbol_ref}, this is used as a flag for machine-specific purposes.
Stored in the @code{volatil} field and printed as @samp{/v}.
+@findex SYMBOL_REF_USED
+@cindex @code{used}, in @code{symbol_ref}
+@item SYMBOL_REF_USED (@var{x})
+In a @code{symbol_ref}, indicates that @var{x} has been used. This is
+normally only used to ensure that @var{x} is only declared external
+once. Stored in the @code{used} field.
+
@findex SYMBOL_REF_WEAK
@cindex @code{symbol_ref} and @samp{/i}
@cindex @code{integrated}, in @code{symbol_ref}
@item SYMBOL_REF_WEAK (@var{x})
In a @code{symbol_ref}, indicates that @var{x} has been declared weak.
Stored in the @code{integrated} field and printed as @samp{/i}.
-
-@findex LABEL_OUTSIDE_LOOP_P
-@cindex @code{label_ref} and @samp{/s}
-@cindex @code{in_struct}, in @code{label_ref}
-@item LABEL_OUTSIDE_LOOP_P
-In @code{label_ref} expressions, nonzero if this is a reference to a
-label that is outside the innermost loop containing the reference to the
-label. Stored in the @code{in_struct} field and printed as @samp{/s}.
-
-@findex INSN_DELETED_P
-@cindex @code{volatil}, in @code{insn}
-@item INSN_DELETED_P (@var{insn})
-In an insn, nonzero if the insn has been deleted. Stored in the
-@code{volatil} field and printed as @samp{/v}.
-
-@findex INSN_ANNULLED_BRANCH_P
-@cindex @code{insn} and @samp{/u}
-@cindex @code{unchanging}, in @code{insn}
-@item INSN_ANNULLED_BRANCH_P (@var{insn})
-In an @code{insn} in the delay slot of a branch insn, indicates that an
-annulling branch should be used. See the discussion under
-@code{sequence} below. Stored in the @code{unchanging} field and printed
-as @samp{/u}.
-
-@findex INSN_FROM_TARGET_P
-@cindex @code{insn} and @samp{/s}
-@cindex @code{in_struct}, in @code{insn}
-@cindex @samp{/s} in RTL dump
-@item INSN_FROM_TARGET_P (@var{insn})
-In an @code{insn} in a delay slot of a branch, indicates that the insn
-is from the target of the branch. If the branch insn has
-@code{INSN_ANNULLED_BRANCH_P} set, this insn will only be executed if
-the branch is taken. For annulled branches with
-@code{INSN_FROM_TARGET_P} clear, the insn will be executed only if the
-branch is not taken. When @code{INSN_ANNULLED_BRANCH_P} is not set,
-this insn will always be executed. Stored in the @code{in_struct}
-field and printed as @samp{/s}.
-
-@findex CONSTANT_POOL_ADDRESS_P
-@cindex @code{symbol_ref} and @samp{/u}
-@cindex @code{unchanging}, in @code{symbol_ref}
-@item CONSTANT_POOL_ADDRESS_P (@var{x})
-Nonzero in a @code{symbol_ref} if it refers to part of the current
-function's ``constants pool''. These are addresses close to the
-beginning of the function, and GCC assumes they can be addressed
-directly (perhaps with the help of base registers). Stored in the
-@code{unchanging} field and printed as @samp{/u}.
-
-@findex CONST_CALL_P
-@cindex @code{call_insn} and @samp{/u}
-@cindex @code{unchanging}, in @code{call_insn}
-@item CONST_CALL_P (@var{x})
-In a @code{call_insn}, indicates that the insn represents a call to a const
-function. Stored in the @code{unchanging} field and printed as @samp{/u}.
-
-@findex LABEL_PRESERVE_P
-@cindex @code{code_label} and @samp{/i}
-@cindex @code{in_struct}, in @code{code_label}
-@item LABEL_PRESERVE_P (@var{x})
-In a @code{code_label}, indicates that the label can never be deleted.
-Labels referenced by a non-local goto will have this bit set. Stored
-in the @code{in_struct} field and printed as @samp{/s}.
-
-@findex SCHED_GROUP_P
-@cindex @code{insn} and @samp{/i}
-@cindex @code{in_struct}, in @code{insn}
-@item SCHED_GROUP_P (@var{insn})
-During instruction scheduling, in an insn, indicates that the previous insn
-must be scheduled together with this insn. This is used to ensure that
-certain groups of instructions will not be split up by the instruction
-scheduling pass, for example, @code{use} insns before a @code{call_insn} may
-not be separated from the @code{call_insn}. Stored in the @code{in_struct}
-field and printed as @samp{/s}.
@end table
-These are the fields which the above macros refer to:
+These are the fields to which the above macros refer:
@table @code
-@findex used
-@item used
-Normally, this flag is used only momentarily, at the end of RTL
-generation for a function, to count the number of times an expression
-appears in insns. Expressions that appear more than once are copied,
-according to the rules for shared structure (@pxref{Sharing}).
+@findex call
+@cindex @samp{/c} in RTL dump
+@item call
+In the @code{LOG_LINKS} of an @code{insn_list} during scheduling, 1 means that
+the cost of executing an instruction through the link is zero.
-In a @code{symbol_ref}, it indicates that an external declaration for
-the symbol has already been written.
+In an RTL dump, this flag is represented as @samp{/c}.
-In a @code{reg}, it is used by the leaf register renumbering code to ensure
-that each register is only renumbered once.
+@findex frame_related
+@cindex @samp{/f} in RTL dump
+@item frame_related
+In an @code{insn} or @code{set} expression, 1 means that it is part of
+a function prologue and sets the stack pointer, sets the frame pointer,
+saves a register, or sets up a temporary register to use in place of the
+frame pointer.
-@findex volatil
-@item volatil
-This flag is used in @code{mem}, @code{symbol_ref} and @code{reg}
-expressions and in insns. In RTL dump files, it is printed as
-@samp{/v}.
+In @code{reg} expressions, 1 means that the register holds a pointer.
-@cindex volatile memory references
-In a @code{mem} expression, it is 1 if the memory reference is volatile.
-Volatile memory references may not be deleted, reordered or combined.
+In @code{symbol_ref} expressions, 1 means that the reference addresses
+this function's string constant pool.
-In a @code{symbol_ref} expression, it is used for machine-specific
-purposes.
-
-In a @code{reg} expression, it is 1 if the value is a user-level variable.
-0 indicates an internal compiler temporary.
+In @code{mem} expressions, 1 means that the reference is to a scalar.
-In an insn, 1 means the insn has been deleted.
+In an RTL dump, this flag is represented as @samp{/f}.
@findex in_struct
+@cindex @samp{/s} in RTL dump
@item in_struct
In @code{mem} expressions, it is 1 if the memory datum referred to is
all or part of a structure or array; 0 if it is (or might be) a scalar
might point to a scalar variable. This information allows the compiler
to determine something about possible cases of aliasing.
-In an insn in the delay slot of a branch, 1 means that this insn is from
-the target of the branch.
-
-During instruction scheduling, in an insn, 1 means that this insn must be
-scheduled as part of a group together with the previous insn.
-
In @code{reg} expressions, it is 1 if the register has its entire life
contained within the test expression of some loop.
label that would have been deleted is replaced with a @code{note} of type
@code{NOTE_INSN_DELETED_LABEL}.
+In an @code{insn} during dead-code elimination, 1 means that the insn is
+dead code.
+
+In an @code{insn} during reorg for an insn in the delay slot of a branch,
+1 means that this insn is from the target of the branch.
+
+In an @code{insn} during instruction scheduling, 1 means that this insn
+must be scheduled as part of a group together with the previous insn.
+
In an RTL dump, this flag is represented as @samp{/s}.
+@findex integrated
+@cindex @samp{/i} in RTL dump
+@item integrated
+In an @code{insn}, @code{insn_list}, or @code{const}, 1 means the RTL was
+produced by procedure integration.
+
+In @code{reg} expressions, 1 means the register contains
+the value to be returned by the current function. On
+machines that pass parameters in registers, the same register number
+may be used for parameters as well, but this flag is not set on such
+uses.
+
+In @code{symbol_ref} expressions, 1 means the referenced symbol is weak.
+
+In an RTL dump, this flag is represented as @samp{/i}.
+
+@findex jump
+@cindex @samp{/j} in RTL dump
+@item jump
+In a @code{mem} expression, 1 means we should keep the alias set for this
+mem unchanged when we access a component.
+
+In a @code{set}, 1 means it is for a return.
+
+In a @code{call_insn}, 1 means it is a sibling call.
+
+In the @code{LOG_LINKS} of an @code{insn_list} during scheduling, 1 means the
+cost of executing an instruction through the link varies and is unchanging.
+
+In an RTL dump, this flag is represented as @samp{/j}.
+
@findex unchanging
+@cindex @samp{/u} in RTL dump
@item unchanging
In @code{reg} and @code{mem} expressions, 1 means
that the value of the expression never changes.
In @code{subreg} expressions, it is 1 if the @code{subreg} references an
unsigned object whose mode has been promoted to a wider mode.
-In an insn, 1 means that this is an annulling branch.
+In an @code{insn}, 1 means that this is an annulling branch.
In a @code{symbol_ref} expression, 1 means that this symbol addresses
-something in the per-function constants pool.
+something in the per-function constant pool.
-In a @code{call_insn}, 1 means that this instruction is a call to a
-const function.
+In a @code{call_insn}, @code{note}, or an @code{expr_list} of notes,
+1 means that this instruction is a call to a const or pure function.
In an RTL dump, this flag is represented as @samp{/u}.
-@findex integrated
-@item integrated
-In some kinds of expressions, including insns, this flag means the
-rtl was produced by procedure integration.
+@findex used
+@item used
+This flag is used directly (without an access macro) at the end of RTL
+generation for a function, to count the number of times an expression
+appears in insns. Expressions that appear more than once are copied,
+according to the rules for shared structure (@pxref{Sharing}).
-In a @code{reg} expression, this flag indicates the register
-containing the value to be returned by the current function. On
-machines that pass parameters in registers, the same register number
-may be used for parameters as well, but this flag is not set on such
-uses.
+For a @code{reg}, it is used directly (without an access macro) by the
+leaf register renumbering code to ensure that each register is only
+renumbered once.
+
+In a @code{symbol_ref}, it indicates that an external declaration for
+the symbol has already been written.
+
+@findex volatil
+@cindex @samp{/v} in RTL dump
+@item volatil
+@cindex volatile memory references
+In a @code{mem} or @code{asm_operands} expression, it is 1 if the memory
+reference is volatile. Volatile memory references may not be deleted,
+reordered or combined.
+
+In a @code{symbol_ref} expression, it is used for machine-specific
+purposes.
+
+In a @code{reg} expression, it is 1 if the value is a user-level variable.
+0 indicates an internal compiler temporary.
+
+In an @code{insn}, 1 means the insn has been deleted.
+
+In @code{label_ref} and @code{reg_label} expressions, 1 means a reference
+to a non-local label.
+
+In an RTL dump, this flag is represented as @samp{/v}.
@end table
@node Machine Modes
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