* config/tc-mips.c (mips_set_options): Add sym32 field.

	(mips_opts): Initialize it.
	(HAVE_32BIT_ADDRESSES): Set to true if pointers are 32 bits wide.
	(HAVE_64BIT_ADDRESSES): Redefine as !HAVE_32BIT_ADDRESSES.
	(HAVE_32BIT_SYMBOLS, HAVE_64BIT_SYMBOLS): New macros.
	(load_address): Use HAVE_64BIT_SYMBOLS instead of HAVE_64BIT_ADDRESSES
	when deciding whether to use a symbolic %highest/%higher expansion.
	(macro): Likewise.  Remove o64/n32 linux hack.  Always use
	ADDRESS_ADD*_INSN for address addition in the expansion of "dla"
	and "la".  Handle constants separately from symbolic expressions in
	the "ld_st:" case, using 64-bit arithmetic if HAVE_64BIT_ADDRESSES
	and using load_register to load the high part of the address.
	(OPTION_MSYM32, OPTION_NO_MSYM32): New macros.
	(OPTION_ELF_BASE): Bump by 2.
	(md_longopts): Add entries for -msym32 and -mno-sym32.
	(md_parse_option): Handle them.
	(usage): Document them.
	(s_mipsset): Handle ".set sym32" and ".set nosym32".
	(s_cpload, s_cpsetup): Use HAVE_64BIT_SYMBOLS instead of
	HAVE_64BIT_ADDRESSES to detect 64-bit values of "_gp".
	* doc/c-mips.texi: Document ".set sym32", ".set nosym32",
	-msym32 and -mno-sym32.

1 files changed, 63 insertions, 0 deletions

diff --git a/gas/doc/c-mips.texi b/gas/doc/c-mips.texi
index 6446c92..b62b7eb 100644
--- a/gas/doc/c-mips.texi
+++ b/gas/doc/c-mips.texi
@@ -26,6 +26,7 @@ Assembly Language Programming'' in the same work.
 * MIPS Object:: 	ECOFF object code
 * MIPS Stabs::  	Directives for debugging information
 * MIPS ISA::    	Directives to override the ISA level
+* MIPS symbol sizes::   Directives to override the size of symbols
 * MIPS autoextend::	Directives for extending MIPS 16 bit instructions
 * MIPS insn::		Directive to mark data as an instruction
 * MIPS option stack::	Directives to save and restore options
@@ -197,6 +198,13 @@ identical to @samp{-march=@var{cpu}}.
 Record which ABI the source code uses.  The recognized arguments
 are: @samp{32}, @samp{n32}, @samp{o64}, @samp{64} and @samp{eabi}.
 
+@item -msym32
+@itemx -mno-sym32
+@cindex -msym32
+@cindex -mno-sym32
+Equivalent to adding @code{.set sym32} or @code{.set nosym32} to
+the beginning of the assembler input.  @xref{MIPS symbol sizes}.
+
 @cindex @code{-nocpp} ignored (MIPS)
 @item -nocpp
 This option is ignored.  It is accepted for command-line compatibility with
@@ -297,6 +305,61 @@ not by traditional @sc{mips} debuggers (this enhancement is required to fully
 support C++ debugging).  These directives are primarily used by compilers, not
 assembly language programmers!
 
+@node MIPS symbol sizes
+@section Directives to override the size of symbols
+
+@cindex @code{.set sym32}
+@cindex @code{.set nosym32}
+The n64 ABI allows symbols to have any 64-bit value.  Although this
+provides a great deal of flexibility, it means that some macros have
+much longer expansions than their 32-bit counterparts.  For example,
+the non-PIC expansion of @samp{dla $4,sym} is usually:
+
+@smallexample
+lui     $4,%highest(sym)
+lui     $1,%hi(sym)
+daddiu  $4,$4,%higher(sym)
+daddiu  $1,$1,%lo(sym)
+dsll32  $4,$4,0
+daddu   $4,$4,$1
+@end smallexample
+
+whereas the 32-bit expansion is simply:
+
+@smallexample
+lui     $4,%hi(sym)
+daddiu  $4,$4,%lo(sym)
+@end smallexample
+
+n64 code is sometimes constructed in such a way that all symbolic
+constants are known to have 32-bit values, and in such cases, it's
+preferable to use the 32-bit expansion instead of the 64-bit
+expansion.
+
+You can use the @code{.set sym32} directive to tell the assembler
+that, from this point on, all expressions of the form
+@samp{@var{symbol}} or @samp{@var{symbol} + @var{offset}}
+have 32-bit values.  For example:
+
+@smallexample
+.set sym32
+dla     $4,sym
+lw      $4,sym+16
+sw      $4,sym+0x8000($4)
+@end smallexample
+
+will cause the assembler to treat @samp{sym}, @code{sym+16} and
+@code{sym+0x8000} as 32-bit values.  The handling of non-symbolic
+addresses is not affected.
+
+The directive @code{.set nosym32} ends a @code{.set sym32} block and
+reverts to the normal behavior.  It is also possible to change the
+symbol size using the command-line options @option{-msym32} and
+@option{-mno-sym32}.
+
+These options and directives are always accepted, but at present,
+they have no effect for anything other than n64.
+
 @node MIPS ISA
 @section Directives to override the ISA level