MIPS/GCC/doc: Fix `d' constraint description

Revert a part of the `d' constraint documentation update made with
commit 111868 ("Use define_constraint for MIPS"),
<https://gcc.gnu.org/ml/gcc-patches/2006-03/msg00460.html>,
<https://gcc.gnu.org/ml/gcc-patches/2006-03/msg00541.html>, which
inadvertently made the registers covered to be referred to as "address"
rather than "general-purpose" registers, and then further clarify the
set of registers allowed with MIPS16 code.

	* config/mips/constraints.md (d): Fix documentation.
	* doc/md.texi (Machine Constraints): Update accordingly.

From-SVN: r240546

gcc/ChangeLog

+2016-09-27  Maciej W. Rozycki  <macro@imgtec.com>
+
+	* config/mips/constraints.md (d): Fix documentation.
+	* doc/md.texi (Machine Constraints): Update accordingly.
+
 2016-09-27  Richard Biener  <rguenther@suse.de>
 
 	* dwarf2out.c (dwarf2out_init): Move text_section_line_info,

gcc/config/mips/constraints.md

@@ -20,8 +20,8 @@
 ;; Register constraints
 
 (define_register_constraint "d" "TARGET_MIPS16 ? M16_REGS : GR_REGS"
-  "An address register.  This is equivalent to @code{r} unless
-   generating MIPS16 code.")
+  "A general-purpose register.  This is equivalent to @code{r} unless
+   generating MIPS16 code, in which case the MIPS16 register set is used.")
 
 (define_register_constraint "t" "T_REG"
   "@internal")

gcc/doc/md.texi

@@ -2582,8 +2582,8 @@ A status register (@code{rmsr}, @code{$fcc1} to @code{$fcc7}).
 @item MIPS---@file{config/mips/constraints.md}
 @table @code
 @item d
-An address register.  This is equivalent to @code{r} unless
-generating MIPS16 code.
+A general-purpose register.  This is equivalent to @code{r} unless
+generating MIPS16 code, in which case the MIPS16 register set is used.
 
 @item f
 A floating-point register (if available).