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rtl.texi: Mention that besides as a CODE_LABEL...

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* doc/rtl.texi: Mention that besides as a CODE_LABEL, a label can
	sometimes be represented as a NOTE of type
	NOTE_INSN_DELETED_LABEL.
	(Insns): Document NOTE_INSN_DELETED_LABEL.

From-SVN: r45378
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Hans-Peter Nilsson 2001-09-04 13:47:28 +00:00 committed by Hans-Peter Nilsson
parent 24697ca0c5
commit ba72e5a66f
2 changed files with 26 additions and 6 deletions
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@ -1,3 +1,10 @@
2001-09-04 Hans-Peter Nilsson <hp@axis.com>
* doc/rtl.texi: Mention that besides as a CODE_LABEL, a label can
sometimes be represented as a NOTE of type
NOTE_INSN_DELETED_LABEL.
(Insns): Document NOTE_INSN_DELETED_LABEL.
2001-09-04 Nathan Sidwell <nathan@codesourcery.com>
* c-common.h (tree_dump_index): Add more comments.

25
gcc/doc/rtl.texi
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@ -659,7 +659,9 @@ outside the innermost loop containing the insn in which the @code{label_ref}
was found.
In @code{code_label} expressions, it is 1 if the label may never be deleted.
This is used for labels which are the target of non-local gotos.
This is used for labels which are the target of non-local gotos. Such a
label that would have been deleted is replaced with a @code{note} of type
@code{NOTE_INSN_DELETED_LABEL}.
In an RTL dump, this flag is represented as @samp{/s}.
@ -1080,9 +1082,9 @@ Usually that is the only mode for which a symbol is directly valid.
@findex label_ref
@item (label_ref @var{label})
Represents the value of an assembler label for code. It contains one
operand, an expression, which must be a @code{code_label} that appears
in the instruction sequence to identify the place where the label
should go.
operand, an expression, which must be a @code{code_label} or a @code{note}
of type @code{NOTE_INSN_DELETED_LABEL} that appears in the instruction
sequence to identify the place where the label should go.
The reason for using a distinct expression type for code label
references is so that jump optimization can distinguish them.
@ -2625,6 +2627,9 @@ When a @code{code_label} appears in an RTL expression, it normally
appears within a @code{label_ref} which represents the address of
the label, as a number.
Besides as a @code{code_label}, a label can also be represented as a
@code{note} of type @code{NOTE_INSN_DELETED_LABEL}.
@findex LABEL_NUSES
The field @code{LABEL_NUSES} is only defined once the jump optimization
phase is completed and contains the number of times this label is
@ -2667,6 +2672,12 @@ must contain a null pointer):
Such a note is completely ignorable. Some passes of the compiler
delete insns by altering them into notes of this kind.
@findex NOTE_INSN_DELETED_LABEL
@item NOTE_INSN_DELETED_LABEL
This marks what used to be a @code{code_label}, but was not used for other
purposes than taking its address and was transformed to mark that no
code jumps to it.
@findex NOTE_INSN_BLOCK_BEG
@findex NOTE_INSN_BLOCK_END
@item NOTE_INSN_BLOCK_BEG
@ -2681,7 +2692,8 @@ of debugging information.
@itemx NOTE_INSN_EH_REGION_END
These types of notes indicate the position of the beginning and end of a
level of scoping for exception handling. @code{NOTE_BLOCK_NUMBER}
identifies which @code{CODE_LABEL} is associated with the given region.
identifies which @code{CODE_LABEL} or @code{note} of type
@code{NOTE_INSN_DELETED_LABEL} is associated with the given region.
@findex NOTE_INSN_LOOP_BEG
@findex NOTE_INSN_LOOP_END
@ -2876,7 +2888,8 @@ last insns, respectively.
@findex REG_LABEL
@item REG_LABEL
This insn uses @var{op}, a @code{code_label}, but is not a
This insn uses @var{op}, a @code{code_label} or a @code{note} of type
@code{NOTE_INSN_DELETED_LABEL}, but is not a
@code{jump_insn}, or it is a @code{jump_insn} that required the label to
be held in a register. The presence of this note allows jump
optimization to be aware that @var{op} is, in fact, being used, and flow