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_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}
@end table
@findex subreg
-@item (subreg:@var{m} @var{reg} @var{wordnum})
+@item (subreg:@var{m} @var{reg} @var{bytenum})
@code{subreg} expressions are used to refer to a register in a machine
mode other than its natural one, or to refer to one register of
-a multi-word @code{reg} that actually refers to several registers.
+a multi-part @code{reg} that actually refers to several registers.
Each pseudo-register has a natural mode. If it is necessary to
operate on it in a different mode---for example, to perform a fullword
move instruction on a pseudo-register that contains a single
byte---the pseudo-register must be enclosed in a @code{subreg}. In
-such a case, @var{wordnum} is zero.
+such a case, @var{bytenum} is zero.
Usually @var{m} is at least as narrow as the mode of @var{reg}, in which
case it is restricting consideration to only the bits of @var{reg} that
@code{TImode} can indicate values longer than a word, values which
usually require two or more consecutive registers. To access one of the
registers, use a @code{subreg} with mode @code{SImode} and a
-@var{wordnum} that says which register.
+@var{bytenum} offset that says which register.
Storing in a non-paradoxical @code{subreg} has undefined results for
bits belonging to the same word as the @code{subreg}. This laxity makes
@cindex @code{WORDS_BIG_ENDIAN}, effect on @code{subreg}
The compilation parameter @code{WORDS_BIG_ENDIAN}, if set to 1, says
-that word number zero is the most significant part; otherwise, it is
-the least significant part.
+that byte number zero is part of the most significant word; otherwise,
+it is part of the least significant word.
+
+@cindex @code{BYTES_BIG_ENDIAN}, effect on @code{subreg}
+The compilation parameter @code{BYTES_BIG_ENDIAN}, if set to 1, says
+that byte number zero is the most significant byte within a word;
+otherwise, it is the least significant byte within a word.
@cindex @code{FLOAT_WORDS_BIG_ENDIAN}, (lack of) effect on @code{subreg}
On a few targets, @code{FLOAT_WORDS_BIG_ENDIAN} disagrees with
expressions such as these from being formed.
@findex SUBREG_REG
-@findex SUBREG_WORD
+@findex SUBREG_BYTE
The first operand of a @code{subreg} expression is customarily accessed
with the @code{SUBREG_REG} macro and the second operand is customarily
-accessed with the @code{SUBREG_WORD} macro.
+accessed with the @code{SUBREG_BYTE} macro.
@findex scratch
@cindex scratch operands
accessed in the same way and in addition contain a field
@code{JUMP_LABEL} which is defined once jump optimization has completed.
-For simple conditional and unconditional jumps, this field contains the
-@code{code_label} to which this insn will (possibly conditionally)
+For simple conditional and unconditional jumps, this field contains
+the @code{code_label} to which this insn will (possibly conditionally)
branch. In a more complex jump, @code{JUMP_LABEL} records one of the
-labels that the insn refers to; the only way to find the others
-is to scan the entire body of the insn.
+labels that the insn refers to; the only way to find the others is to
+scan the entire body of the insn. In an @code{addr_vec},
+@code{JUMP_LABEL} is @code{NULL_RTX}.
-Return insns count as jumps, but since they do not refer to any labels,
-they have zero in the @code{JUMP_LABEL} field.
+Return insns count as jumps, but since they do not refer to any
+labels, their @code{JUMP_LABEL} is @code{NULL_RTX}.
@findex call_insn
@item call_insn
accessed in the same way and in addition contain a field
@code{CALL_INSN_FUNCTION_USAGE}, which contains a list (chain of
@code{expr_list} expressions) containing @code{use} and @code{clobber}
-expressions that denote hard registers used or clobbered by the called
-function. A register specified in a @code{clobber} in this list is
-modified @emph{after} the execution of the @code{call_insn}, while a
-register in a @code{clobber} in the body of the @code{call_insn} is
-clobbered before the insn completes execution. @code{clobber}
-expressions in this list augment registers specified in
+expressions that denote hard registers and @code{MEM}s used or
+clobbered by the called function.
+
+A @code{MEM} generally points to a stack slots in which arguments passed
+to the libcall by reference (@pxref{Register Arguments,
+FUNCTION_ARG_PASS_BY_REFERENCE}) are stored. If the argument is
+caller-copied (@pxref{Register Arguments, FUNCTION_ARG_CALLEE_COPIES}),
+the stack slot will be mentioned in @code{CLOBBER} and @code{USE}
+entries; if it's callee-copied, only a @code{USE} will appear, and the
+@code{MEM} may point to addresses that are not stack slots. These
+@code{MEM}s are used only in libcalls, because, unlike regular function
+calls, @code{CONST_CALL}s (which libcalls generally are, @pxref{Flags,
+CONST_CALL_P}) aren't assumed to read and write all memory, so flow
+would consider the stores dead and remove them. Note that, since a
+libcall must never return values in memory (@pxref{Aggregate Return,
+RETURN_IN_MEMORY}), there will never be a @code{CLOBBER} for a memory
+address holding a return value.
+
+@code{CLOBBER}ed registers in this list augment registers specified in
@code{CALL_USED_REGISTERS} (@pxref{Register Basics}).
@findex code_label
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