This adjusts equate handling by

- allowing true forward references (which will always assume the referenced
  symbols have at the point of use) through the new .eqv pseudo-op and the
  new == operator
- disallowing changing .equiv-generated equates (so that the protection this
  provides is both forward and backward)
- snapshotting equates when their value gets changed so that previous uses
  don't get affected by the new value.
- allowing expressions in places where absolute expressions (or register
  names) are needed which were not completely resolvable at the point of
  their definition but which are fully resolvable at the point of use

In addition it fixes PR/288.

1 files changed, 13 insertions, 1 deletions

diff --git a/gas/doc/as.texinfo b/gas/doc/as.texinfo
index 1d9ae0c..2b3e4c2 100644
--- a/gas/doc/as.texinfo
+++ b/gas/doc/as.texinfo
@@ -3119,7 +3119,9 @@ provides a special directive @code{.label} for defining labels more flexibly.
 A symbol can be given an arbitrary value by writing a symbol, followed
 by an equals sign @samp{=}, followed by an expression
 (@pxref{Expressions}).  This is equivalent to using the @code{.set}
-directive.  @xref{Set,,@code{.set}}.
+directive.  @xref{Set,,@code{.set}}.  In the same way, using a double
+equals sign @samp{=}@samp{=} here represents an equivalent of the
+@code{.eqv} directive.  @xref{Eqv,,@code{.eqv}}.
 
 @node Symbol Names
 @section Symbol Names
@@ -3716,6 +3718,7 @@ Some machine configurations provide additional directives.
 * Endif::                       @code{.endif}
 * Equ::                         @code{.equ @var{symbol}, @var{expression}}
 * Equiv::                       @code{.equiv @var{symbol}, @var{expression}}
+* Eqv::                         @code{.eqv @var{symbol}, @var{expression}}
 * Err::				@code{.err}
 * Error::			@code{.error @var{string}}
 * Exitm::			@code{.exitm}
@@ -4283,6 +4286,15 @@ Except for the contents of the error message, this is roughly equivalent to
 .endif
 .equ SYM,VAL
 @end smallexample
+plus it protects the symbol from later redefinition.
+
+@node Eqv
+@section @code{.eqv @var{symbol}, @var{expression}}
+@cindex @code{eqv} directive
+The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
+evaluate the expression or any part of it immediately.  Instead each time
+the resulting symbol is used in an expression, a snapshot of its current
+value is taken.
 
 @node Err
 @section @code{.err}