1 files changed, 46 insertions, 35 deletions
diff --git a/gcc/doc/rtl.texi b/gcc/doc/rtl.texi
index 1c9a4e49230..605aad05f25 100644
--- a/gcc/doc/rtl.texi
+++ b/gcc/doc/rtl.texi
@@ -1,4 +1,4 @@
-@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, 2003
 @c Free Software Foundation, Inc.
 @c This is part of the GCC manual.
 @c For copying conditions, see the file gcc.texi.
@@ -244,7 +244,7 @@ from an @samp{md} file, the vector value of this operand may be omitted.
 An omitted vector is effectively the same as a vector of no elements.
 
 @item B
-@samp{B} indicates a pointer to basic block strucure.
+@samp{B} indicates a pointer to basic block structure.
 
 @item 0
 @samp{0} means a slot whose contents do not fit any normal category.
@@ -608,9 +608,22 @@ Stored in the @code{integrated} field and printed as @samp{/i}.
 @cindex @code{concat} and @samp{/u}
 @cindex @code{unchanging}, in @code{reg} and @code{mem}
 @item RTX_UNCHANGING_P (@var{x})
-Nonzero in a @code{reg}, @code{mem}, or @code{concat} if the memory
-is set at most once,
-anywhere.  This does not mean that it is function invariant.
+Nonzero in a @code{reg}, @code{mem}, or @code{concat} if the register or
+memory is set at most once, anywhere.  This does not mean that it is
+function invariant.
+
+GCC uses this flag to determine whether two references conflict.  As
+implemented by @code{true_dependence} in @file{alias.c} for memory
+references, unchanging memory can't conflict with non-unchanging memory;
+a non-unchanging read can conflict with a non-unchanging write; an
+unchanging read can conflict with an unchanging write (since there may
+be a single store to this address to initialize it); and an unchanging
+store can conflict with a non-unchanging read.  This means we must make
+conservative assumptions when choosing the value of this flag for a
+memory reference to an object containing both unchanging and
+non-unchanging fields: we must set the flag when writing to the object
+and clear it when reading from the object.
+
 Stored in the @code{unchanging} field and printed as @samp{/u}.
 
 @findex SCHED_GROUP_P
@@ -687,13 +700,6 @@ 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}
-@cindex @code{volatil}, in @code{symbol_ref}
-@item SYMBOL_REF_FLAG (@var{x})
-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})
@@ -707,6 +713,17 @@ once.  Stored in the @code{used} field.
 @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 SYMBOL_REF_FLAG
+@cindex @code{symbol_ref} and @samp{/v}
+@cindex @code{volatil}, in @code{symbol_ref}
+@item SYMBOL_REF_FLAG (@var{x})
+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}.
+
+Most uses of @code{SYMBOL_REF_FLAG} are historic and may be subsumed
+by @code{SYMBOL_REF_FLAGS}.  Certainly use of @code{SYMBOL_REF_FLAGS}
+is mandatory if the target requires more than one bit of storage.
 @end table
 
 These are the fields to which the above macros refer:
@@ -1854,14 +1871,14 @@ valid.
 Comparison operators test a relation on two operands and are considered
 to represent a machine-dependent nonzero value described by, but not
 necessarily equal to, @code{STORE_FLAG_VALUE} (@pxref{Misc})
-if the relation holds, or zero if it does not.  The mode of the
-comparison operation is independent of the mode of the data being
-compared.  If the comparison operation is being tested (e.g., the first
-operand of an @code{if_then_else}), the mode must be @code{VOIDmode}.
-If the comparison operation is producing data to be stored in some
-variable, the mode must be in class @code{MODE_INT}.  All comparison
-operations producing data must use the same mode, which is
-machine-specific.
+if the relation holds, or zero if it does not, for comparison operators
+whose results have a `MODE_INT' mode, and
+@code{FLOAT_STORE_FLAG_VALUE} (@pxref{Misc}) if the relation holds, or
+zero if it does not, for comparison operators that return floating-point
+values.  The mode of the comparison operation is independent of the mode
+of the data being compared.  If the comparison operation is being tested
+(e.g., the first operand of an @code{if_then_else}), the mode must be
+@code{VOIDmode}.
 
 @cindex condition codes
 There are two ways that comparison operations may be used.  The
@@ -2195,9 +2212,9 @@ the operands of these.
 @item (set @var{lval} @var{x})
 Represents the action of storing the value of @var{x} into the place
 represented by @var{lval}.  @var{lval} must be an expression
-representing a place that can be stored in: @code{reg} (or @code{subreg}
-or @code{strict_low_part}), @code{mem}, @code{pc}, @code{parallel}, or
-@code{cc0}.
+representing a place that can be stored in: @code{reg} (or @code{subreg},
+@code{strict_low_part} or @code{zero_extract}), @code{mem}, @code{pc},
+@code{parallel}, or @code{cc0}.
 
 If @var{lval} is a @code{reg}, @code{subreg} or @code{mem}, it has a
 machine mode; then @var{x} must be valid for that mode.
@@ -2210,10 +2227,10 @@ rest of the register receives an undefined value.  Likewise, if
 the mode of the register, the rest of the register can be changed in
 an undefined way.
 
-If @var{lval} is a @code{strict_low_part} of a @code{subreg}, then the
-part of the register specified by the machine mode of the
-@code{subreg} is given the value @var{x} and the rest of the register
-is not changed.
+If @var{lval} is a @code{strict_low_part} or @code{zero_extract} 
+of a @code{subreg}, then the part of the register specified by the
+machine mode of the @code{subreg} is given the value @var{x} and
+the rest of the register is not changed.
 
 If @var{lval} is @code{(cc0)}, it has no machine mode, and @var{x} may
 be either a @code{compare} expression or a value that may have any mode.
@@ -2596,7 +2613,7 @@ Here is an example of its use:
 This says to modify pseudo register 42 by adding the contents of pseudo
 register 48 to it, after the use of what ever 42 points to.
 
-@findex post_modify
+@findex pre_modify
 @item (pre_modify:@var{m} @var{x} @var{expr})
 Similar except side effects happen before the use.
 @end table
@@ -2841,7 +2858,7 @@ labels: @code{LABEL_NORMAL}, @code{LABEL_STATIC_ENTRY},
 that do not have type @code{LABEL_NORMAL} are @dfn{alternate entry
 points} to the current function.  These may be static (visible only in
 the containing translation unit), global (exposed to all translation
-units), or weak (global, but can be overriden by another symbol with the
+units), or weak (global, but can be overridden by another symbol with the
 same name).
 
 Much of the compiler treats all four kinds of label identically.  Some
@@ -3254,12 +3271,6 @@ are stored in the @code{REG_NOTES} field of an insn as an
 @code{expr_list}.
 
 @table @code
-@findex REG_EXEC_COUNT
-@item REG_EXEC_COUNT
-This is used to indicate the number of times a basic block was executed
-according to the profile data.  The note is attached to the first insn in
-the basic block.
-
 @findex REG_BR_PROB
 @item REG_BR_PROB
 This is used to specify the ratio of branches to non-branches of a