* doc/rtl.texi (Machine Modes): Document QQ, HQ, SQ, DQ, TQ,

[pf3gnuchains/gcc-fork.git] / gcc / doc / rtl.texi

diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index 1f9372e..fb38f7f 100644 (file)
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -1,5 +1,5 @@
 @c Copyright (C) 1988, 1989, 1992, 1994, 1997, 1998, 1999, 2000, 2001, 2002,
 @c Copyright (C) 1988, 1989, 1992, 1994, 1997, 1998, 1999, 2000, 2001, 2002,

-@c 2003, 2004, 2005
+@c 2003, 2004, 2005, 2006, 2007

 @c Free Software Foundation, Inc.
 @c This is part of the GCC manual.
 @c For copying conditions, see the file gcc.texi.
 @c Free Software Foundation, Inc.
 @c This is part of the GCC manual.
 @c For copying conditions, see the file gcc.texi.


@@ -138,7 +138,7 @@ wanted.  The written form of this is @code{(nil)}.
 The various expression codes are divided into several @dfn{classes},
 which are represented by single characters.  You can determine the class
 of an RTX code with the macro @code{GET_RTX_CLASS (@var{code})}.
 The various expression codes are divided into several @dfn{classes},
 which are represented by single characters.  You can determine the class
 of an RTX code with the macro @code{GET_RTX_CLASS (@var{code})}.

-Currently, @file{rtx.def} defines these classes:
+Currently, @file{rtl.def} defines these classes:

 
 @table @code
 @item RTX_OBJ
 
 @table @code
 @item RTX_OBJ


@@ -455,6 +455,16 @@ that is, some sort of constant.  In this case, the @code{symbol_ref}
 is an entry in the per-file constant pool; again, there is no associated
 front end symbol table entry.
 
 is an entry in the per-file constant pool; again, there is no associated
 front end symbol table entry.
 

+@findex SYMBOL_REF_CONSTANT
+@item SYMBOL_REF_CONSTANT (@var{x})
+If @samp{CONSTANT_POOL_ADDRESS_P (@var{x})} is true, this is the constant
+pool entry for @var{x}.  It is null otherwise.
+
+@findex SYMBOL_REF_DATA
+@item SYMBOL_REF_DATA (@var{x})
+A field of opaque type used to store @code{SYMBOL_REF_DECL} or
+@code{SYMBOL_REF_CONSTANT}.
+

 @findex SYMBOL_REF_FLAGS
 @item SYMBOL_REF_FLAGS (@var{x})
 In a @code{symbol_ref}, this is used to communicate various predicates
 @findex SYMBOL_REF_FLAGS
 @item SYMBOL_REF_FLAGS (@var{x})
 In a @code{symbol_ref}, this is used to communicate various predicates


@@ -491,11 +501,41 @@ See @code{TARGET_IN_SMALL_DATA_P}.
 This is a multi-bit field accessor that returns the @code{tls_model}
 to be used for a thread-local storage symbol.  It returns zero for
 non-thread-local symbols.
 This is a multi-bit field accessor that returns the @code{tls_model}
 to be used for a thread-local storage symbol.  It returns zero for
 non-thread-local symbols.

+
+@findex SYMBOL_REF_HAS_BLOCK_INFO_P
+@findex SYMBOL_FLAG_HAS_BLOCK_INFO
+@item SYMBOL_FLAG_HAS_BLOCK_INFO
+Set if the symbol has @code{SYMBOL_REF_BLOCK} and
+@code{SYMBOL_REF_BLOCK_OFFSET} fields.
+
+@findex SYMBOL_REF_ANCHOR_P
+@findex SYMBOL_FLAG_ANCHOR
+@cindex @option{-fsection-anchors}
+@item SYMBOL_FLAG_ANCHOR
+Set if the symbol is used as a section anchor.  ``Section anchors''
+are symbols that have a known position within an @code{object_block}
+and that can be used to access nearby members of that block.
+They are used to implement @option{-fsection-anchors}.
+
+If this flag is set, then @code{SYMBOL_FLAG_HAS_BLOCK_INFO} will be too.

 @end table
 
 Bits beginning with @code{SYMBOL_FLAG_MACH_DEP} are available for
 the target's use.
 @end table
 @end table
 
 Bits beginning with @code{SYMBOL_FLAG_MACH_DEP} are available for
 the target's use.
 @end table

+
+@findex SYMBOL_REF_BLOCK
+@item SYMBOL_REF_BLOCK (@var{x})
+If @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})}, this is the
+@samp{object_block} structure to which the symbol belongs,
+or @code{NULL} if it has not been assigned a block.
+
+@findex SYMBOL_REF_BLOCK_OFFSET
+@item SYMBOL_REF_BLOCK_OFFSET (@var{x})
+If @samp{SYMBOL_REF_HAS_BLOCK_INFO_P (@var{x})}, this is the offset of @var{x}
+from the first object in @samp{SYMBOL_REF_BLOCK (@var{x})}.  The value is
+negative if @var{x} has not yet been assigned to a block, or it has not
+been given an offset within that block.

 @end table
 
 @node Flags
 @end table
 
 @node Flags


@@ -568,14 +608,6 @@ 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}.
 
 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{note} and @samp{/i}
 @findex LABEL_PRESERVE_P
 @cindex @code{code_label} and @samp{/i}
 @cindex @code{note} and @samp{/i}


@@ -1081,12 +1113,118 @@ number.  This mode only has 80 meaningful bits (ten bytes).  Some
 processors require such numbers to be padded to twelve bytes, others
 to sixteen; this mode is used for either.
 
 processors require such numbers to be padded to twelve bytes, others
 to sixteen; this mode is used for either.
 

+@findex SDmode
+@item SDmode
+``Single Decimal Floating'' mode represents a four byte decimal
+floating point number (as distinct from conventional binary floating
+point).
+
+@findex DDmode
+@item DDmode
+``Double Decimal Floating'' mode represents an eight byte decimal
+floating point number.
+
+@findex TDmode
+@item TDmode
+``Tetra Decimal Floating'' mode represents a sixteen byte decimal
+floating point number all 128 of whose bits are meaningful.
+

 @findex TFmode
 @item TFmode
 ``Tetra Floating'' mode represents a sixteen byte floating point number
 all 128 of whose bits are meaningful.  One common use is the
 IEEE quad-precision format.
 
 @findex TFmode
 @item TFmode
 ``Tetra Floating'' mode represents a sixteen byte floating point number
 all 128 of whose bits are meaningful.  One common use is the
 IEEE quad-precision format.
 

+@findex QQmode
+@item QQmode
+``Quarter-Fractional'' mode represents a single byte treated as a signed
+fractional number.  The default format is ``s.7''.
+
+@findex HQmode
+@item HQmode
+``Half-Fractional'' mode represents a two-byte signed fractional number.
+The default format is ``s.15''.
+
+@findex SQmode
+@item SQmode
+``Single Fractional'' mode represents a four-byte signed fractional number.
+The default format is ``s.31''.
+
+@findex DQmode
+@item DQmode
+``Double Fractional'' mode represents an eight-byte signed fractional number.
+The default format is ``s.63''.
+
+@findex TQmode
+@item TQmode
+``Tetra Fractional'' mode represents a sixteen-byte signed fractional number.
+The default format is ``s.127''.
+
+@findex UQQmode
+@item UQQmode
+``Unsigned Quarter-Fractional'' mode represents a single byte treated as an
+unsigned fractional number.  The default format is ``.8''.
+
+@findex UHQmode
+@item UHQmode
+``Unsigned Half-Fractional'' mode represents a two-byte unsigned fractional
+number.  The default format is ``.16''.
+
+@findex USQmode
+@item USQmode
+``Unsigned Single Fractional'' mode represents a four-byte unsigned fractional
+number.  The default format is ``.32''.
+
+@findex UDQmode
+@item UDQmode
+``Unsigned Double Fractional'' mode represents an eight-byte unsigned
+fractional number.  The default format is ``.64''.
+
+@findex UTQmode
+@item UTQmode
+``Unsigned Tetra Fractional'' mode represents a sixteen-byte unsigned
+fractional number.  The default format is ``.128''.
+
+@findex HAmode
+@item HAmode
+``Half-Accumulator'' mode represents a two-byte signed accumulator.
+The default format is ``s8.7''.
+
+@findex SAmode
+@item SAmode
+``Single Accumulator'' mode represents a four-byte signed accumulator.
+The default format is ``s16.15''.
+
+@findex DAmode
+@item DAmode
+``Double Accumulator'' mode represents an eight-byte signed accumulator.
+The default format is ``s32.31''.
+
+@findex TAmode
+@item TAmode
+``Tetra Accumulator'' mode represents a sixteen-byte signed accumulator.
+The default format is ``s64.63''.
+
+@findex UHAmode
+@item UHAmode
+``Unsigned Half-Accumulator'' mode represents a two-byte unsigned accumulator.
+The default format is ``8.8''.
+
+@findex USAmode
+@item USAmode
+``Unsigned Single Accumulator'' mode represents a four-byte unsigned
+accumulator.  The default format is ``16.16''.
+
+@findex UDAmode
+@item UDAmode
+``Unsigned Double Accumulator'' mode represents an eight-byte unsigned
+accumulator.  The default format is ``32.32''.
+
+@findex UTAmode
+@item UTAmode
+``Unsigned Tetra Accumulator'' mode represents a sixteen-byte unsigned
+accumulator.  The default format is ``64.64''.
+

 @findex CCmode
 @item CCmode
 ``Condition Code'' mode represents the value of a condition code, which
 @findex CCmode
 @item CCmode
 ``Condition Code'' mode represents the value of a condition code, which


@@ -1173,6 +1311,31 @@ Floating point modes.  By default these are @code{QFmode},
 @code{HFmode}, @code{TQFmode}, @code{SFmode}, @code{DFmode},
 @code{XFmode} and @code{TFmode}.
 
 @code{HFmode}, @code{TQFmode}, @code{SFmode}, @code{DFmode},
 @code{XFmode} and @code{TFmode}.
 

+@findex MODE_DECIMAL_FLOAT
+@item MODE_DECIMAL_FLOAT
+Decimal floating point modes.  By default these are @code{SDmode},
+@code{DDmode} and @code{TDmode}.
+
+@findex MODE_FRACT
+@item MODE_FRACT
+Signed fractional modes.  By default these are @code{QQmode}, @code{HQmode},
+@code{SQmode}, @code{DQmode} and @code{TQmode}.
+
+@findex MODE_UFRACT
+@item MODE_UFRACT
+Unsigned fractional modes.  By default these are @code{UQQmode}, @code{UHQmode},
+@code{USQmode}, @code{UDQmode} and @code{UTQmode}.
+
+@findex MODE_ACCUM
+@item MODE_ACCUM
+Signed accumulator modes.  By default these are @code{HAmode},
+@code{SAmode}, @code{DAmode} and @code{TAmode}.
+
+@findex MODE_UACCUM
+@item MODE_UACCUM
+Unsigned accumulator modes.  By default these are @code{UHAmode},
+@code{USAmode}, @code{UDAmode} and @code{UTAmode}.
+

 @findex MODE_COMPLEX_INT
 @item MODE_COMPLEX_INT
 Complex integer modes.  (These are not currently implemented).
 @findex MODE_COMPLEX_INT
 @item MODE_COMPLEX_INT
 Complex integer modes.  (These are not currently implemented).


@@ -1191,7 +1354,8 @@ Algol or Pascal function variables including a static chain.
 @findex MODE_CC
 @item MODE_CC
 Modes representing condition code values.  These are @code{CCmode} plus
 @findex MODE_CC
 @item MODE_CC
 Modes representing condition code values.  These are @code{CCmode} plus

-any modes listed in the @code{EXTRA_CC_MODES} macro.  @xref{Jump Patterns},
+any @code{CC_MODE} modes listed in the @file{@var{machine}-modes.def}.  
+@xref{Jump Patterns},

 also see @ref{Condition Code}.
 
 @findex MODE_RANDOM
 also see @ref{Condition Code}.
 
 @findex MODE_RANDOM


@@ -1239,6 +1403,14 @@ Returns the size in bytes of a datum of mode @var{m}.
 @item GET_MODE_BITSIZE (@var{m})
 Returns the size in bits of a datum of mode @var{m}.
 
 @item GET_MODE_BITSIZE (@var{m})
 Returns the size in bits of a datum of mode @var{m}.
 

+@findex GET_MODE_IBIT
+@item GET_MODE_IBIT (@var{m})
+Returns the number of integral bits of a datum of fixed-point mode @var{m}.
+
+@findex GET_MODE_FBIT
+@item GET_MODE_FBIT (@var{m})
+Returns the number of fractional bits of a datum of fixed-point mode @var{m}.
+

 @findex GET_MODE_MASK
 @item GET_MODE_MASK (@var{m})
 Returns a bitmask containing 1 for all bits in a word that fit within
 @findex GET_MODE_MASK
 @item GET_MODE_MASK (@var{m})
 Returns a bitmask containing 1 for all bits in a word that fit within


@@ -1504,9 +1676,9 @@ value of @code{FIRST_PARM_OFFSET}.
 @findex VIRTUAL_STACK_VARS_REGNUM
 @cindex @code{FRAME_GROWS_DOWNWARD} and virtual registers
 @item VIRTUAL_STACK_VARS_REGNUM
 @findex VIRTUAL_STACK_VARS_REGNUM
 @cindex @code{FRAME_GROWS_DOWNWARD} and virtual registers
 @item VIRTUAL_STACK_VARS_REGNUM

-If @code{FRAME_GROWS_DOWNWARD} is defined, this points to immediately
-above the first variable on the stack.  Otherwise, it points to the
-first variable on the stack.
+If @code{FRAME_GROWS_DOWNWARD} is defined to a nonzero value, this points
+to immediately above the first variable on the stack.  Otherwise, it points
+to the first variable on the stack.

 
 @cindex @code{STARTING_FRAME_OFFSET} and virtual registers
 @cindex @code{FRAME_POINTER_REGNUM} and virtual registers
 
 @cindex @code{STARTING_FRAME_OFFSET} and virtual registers
 @cindex @code{FRAME_POINTER_REGNUM} and virtual registers


@@ -1720,6 +1892,19 @@ is always @code{Pmode}.  If there are any @code{addressof}
 expressions left in the function after CSE, @var{reg} is forced into the
 stack and the @code{addressof} expression is replaced with a @code{plus}
 expression for the address of its stack slot.
 expressions left in the function after CSE, @var{reg} is forced into the
 stack and the @code{addressof} expression is replaced with a @code{plus}
 expression for the address of its stack slot.

+
+@findex concat
+@item (concat@var{m} @var{rtx} @var{rtx})
+This RTX represents the concatenation of two other RTXs.  This is used
+for complex values.  It should only appear in the RTL attached to
+declarations and during RTL generation.  It should not appear in the
+ordinary insn chain.
+
+@findex concatn
+@item (concatn@var{m} [@var{rtx} ...])
+This RTX represents the concatenation of all the @var{rtx} to make a
+single value.  Like @code{concat}, this should only appear in
+declarations, and not in the insn chain.

 @end table
 
 @node Arithmetic
 @end table
 
 @node Arithmetic


@@ -1827,9 +2012,18 @@ or the first operand must be loaded into a register while its mode is
 still known.
 
 @findex neg
 still known.
 
 @findex neg

+@findex ss_neg
+@cindex negation
+@cindex negation with signed saturation

 @item (neg:@var{m} @var{x})
 @item (neg:@var{m} @var{x})

-Represents the negation (subtraction from zero) of the value represented
-by @var{x}, carried out in mode @var{m}.
+@itemx (ss_neg:@var{m} @var{x})
+These two expressions represent the negation (subtraction from zero) of
+the value represented by @var{x}, carried out in mode @var{m}.  They
+differ in the behavior on overflow of integer modes.  In the case of
+@code{neg}, the negation of the operand may be a number not representable
+in mode @var{m}, in which case it is truncated to @var{m}.  @code{ss_neg}
+ensures that an out-of-bounds result saturates to the maximum or minimum
+representable value.

 
 @findex mult
 @cindex multiplication
 
 @findex mult
 @cindex multiplication


@@ -1936,12 +2130,21 @@ and @var{y}, carried out in machine mode @var{m}, which must be a
 fixed-point mode.
 
 @findex ashift
 fixed-point mode.
 
 @findex ashift

+@findex ss_ashift

 @cindex left shift
 @cindex shift
 @cindex arithmetic shift
 @cindex left shift
 @cindex shift
 @cindex arithmetic shift

+@cindex arithmetic shift with signed saturation

 @item (ashift:@var{m} @var{x} @var{c})
 @item (ashift:@var{m} @var{x} @var{c})

-Represents the result of arithmetically shifting @var{x} left by @var{c}
-places.  @var{x} have mode @var{m}, a fixed-point machine mode.  @var{c}
+@itemx (ss_ashift:@var{m} @var{x} @var{c})
+These two expressions represent the result of arithmetically shifting @var{x}
+left by @var{c} places.  They differ in their behavior on overflow of integer
+modes.  An @code{ashift} operation is a plain shift with no special behavior
+in case of a change in the sign bit; @code{ss_ashift} saturates to the minimum
+or maximum representable value if any of the bits shifted out differs from the
+final sign bit.
+
+@var{x} have mode @var{m}, a fixed-point machine mode.  @var{c}

 be a fixed-point mode or be a constant with mode @code{VOIDmode}; which
 mode is determined by the mode called for in the machine description
 entry for the left-shift instruction.  For example, on the VAX, the mode
 be a fixed-point mode or be a constant with mode @code{VOIDmode}; which
 mode is determined by the mode called for in the machine description
 entry for the left-shift instruction.  For example, on the VAX, the mode


@@ -2012,6 +2215,11 @@ mode @var{m}.  The mode of @var{x} will usually be an integer mode.
 Represents the number of 1-bits modulo 2 in @var{x}, represented as an
 integer of mode @var{m}.  The mode of @var{x} will usually be an integer
 mode.
 Represents the number of 1-bits modulo 2 in @var{x}, represented as an
 integer of mode @var{m}.  The mode of @var{x} will usually be an integer
 mode.

+
+@findex bswap
+@item (bswap:@var{m} @var{x})
+Represents the value @var{x} with the order of bytes reversed, carried out
+in mode @var{m}, which must be a fixed-point machine mode.

 @end table
 
 @node Comparisons
 @end table
 
 @node Comparisons


@@ -2969,14 +3177,7 @@ TARGET_PASS_BY_REFERENCE}) are stored.  If the argument is
 caller-copied (@pxref{Register Arguments, TARGET_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
 caller-copied (@pxref{Register Arguments, TARGET_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{MEM} may point to addresses that are not stack slots.

 
 @code{CLOBBER}ed registers in this list augment registers specified in
 @code{CALL_USED_REGISTERS} (@pxref{Register Basics}).
 
 @code{CLOBBER}ed registers in this list augment registers specified in
 @code{CALL_USED_REGISTERS} (@pxref{Register Basics}).


@@ -3104,17 +3305,10 @@ becomes another virtual start of the loop when considering loop
 invariants.
 
 @findex NOTE_INSN_FUNCTION_BEG
 invariants.
 
 @findex NOTE_INSN_FUNCTION_BEG

-@item NOTE_INSN_FUNCTION_END
+@item NOTE_INSN_FUNCTION_BEG

 Appears at the start of the function body, after the function
 prologue.
 
 Appears at the start of the function body, after the function
 prologue.
 

-@findex NOTE_INSN_FUNCTION_END
-@item NOTE_INSN_FUNCTION_END
-Appears near the end of the function body, just before the label that
-@code{return} statements jump to (on machine where a single instruction
-does not suffice for returning).  This note may be deleted by jump
-optimization.
-

 @end table
 
 These codes are printed symbolically when they appear in debugging dumps.
 @end table
 
 These codes are printed symbolically when they appear in debugging dumps.


@@ -3174,7 +3368,9 @@ file as some small positive or negative offset from a named pattern.
 @item LOG_LINKS (@var{i})
 A list (chain of @code{insn_list} expressions) giving information about
 dependencies between instructions within a basic block.  Neither a jump
 @item LOG_LINKS (@var{i})
 A list (chain of @code{insn_list} expressions) giving information about
 dependencies between instructions within a basic block.  Neither a jump

-nor a label may come between the related insns.
+nor a label may come between the related insns.  These are only used by
+the schedulers and by combine.  This is a deprecated data structure.
+Def-use and use-def chains are now prefered. 

 
 @findex REG_NOTES
 @item REG_NOTES (@var{i})
 
 @findex REG_NOTES
 @item REG_NOTES (@var{i})


@@ -3195,13 +3391,7 @@ This list is originally set up by the flow analysis pass; it is a null
 pointer until then.  Flow only adds links for those data dependencies
 which can be used for instruction combination.  For each insn, the flow
 analysis pass adds a link to insns which store into registers values
 pointer until then.  Flow only adds links for those data dependencies
 which can be used for instruction combination.  For each insn, the flow
 analysis pass adds a link to insns which store into registers values

-that are used for the first time in this insn.  The instruction
-scheduling pass adds extra links so that every dependence will be
-represented.  Links represent data dependencies, antidependencies and
-output dependencies; the machine mode of the link distinguishes these
-three types: antidependencies have mode @code{REG_DEP_ANTI}, output
-dependencies have mode @code{REG_DEP_OUTPUT}, and data dependencies have
-mode @code{VOIDmode}.
+that are used for the first time in this insn.

 
 The @code{REG_NOTES} field of an insn is a chain similar to the
 @code{LOG_LINKS} field but it includes @code{expr_list} expressions in
 
 The @code{REG_NOTES} field of an insn is a chain similar to the
 @code{LOG_LINKS} field but it includes @code{expr_list} expressions in


@@ -3424,13 +3614,18 @@ they simply have mode @code{VOIDmode}, and are printed without any
 descriptive text.
 
 @table @code
 descriptive text.
 
 @table @code

-@findex REG_DEP_ANTI
-@item REG_DEP_ANTI
-This indicates an anti dependence (a write after read dependence).
+@findex REG_DEP_TRUE
+@item REG_DEP_TRUE
+This indicates a true dependence (a read after write dependence).

 
 @findex REG_DEP_OUTPUT
 @item REG_DEP_OUTPUT
 This indicates an output dependence (a write after write dependence).
 
 @findex REG_DEP_OUTPUT
 @item REG_DEP_OUTPUT
 This indicates an output dependence (a write after write dependence).

+
+@findex REG_DEP_ANTI
+@item REG_DEP_ANTI
+This indicates an anti dependence (a write after read dependence).
+

 @end table
 
 These notes describe information gathered from gcov profile data.  They
 @end table
 
 These notes describe information gathered from gcov profile data.  They


@@ -3456,6 +3651,12 @@ of the JUMP@.  The format is a bitmask of ATTR_FLAG_* values.
 This is used on an RTX_FRAME_RELATED_P insn wherein the attached expression
 is used in place of the actual insn pattern.  This is done in cases where
 the pattern is either complex or misleading.
 This is used on an RTX_FRAME_RELATED_P insn wherein the attached expression
 is used in place of the actual insn pattern.  This is done in cases where
 the pattern is either complex or misleading.

+
+@findex REG_LIBCALL_ID
+@item REG_LIBCALL_ID
+This is used to specify that an insn is part of a libcall.  Each libcall
+in a function has a unique id, and all the insns that are part of that
+libcall will have a REG_LIBCALL_ID note attached with the same ID.

 @end table
 
 For convenience, the machine mode in an @code{insn_list} or
 @end table
 
 For convenience, the machine mode in an @code{insn_list} or