[PATCH, docs] Cleanup riscv option docs.

[Jim Wilson <jimw@sifive.com>]

This patch fixes a number of issues with the RISC-V option docs.  Deletes
a non-existent option.  Adds missing default value info.  Deletes some
redundant lines that appear to be from a patch merging error.  Adds missing
docs for the -mexplicit-relocs option.

Tested with a make doc, and viewing the generated gcc.info files to make sure
they are OK.

I'll wait a few days in case a doc maintainer wants to comment, and then will
check it in as is if I don't get any comments.

	gcc/
	* doc/invoke.texi (RISC-V Options): Delete nonexistent -mmemcpy and
	-mno-memcpy options.  For -mplt, -mfdiv, -mdiv, -msave-restore, and
	-mstrict-align, add info on default value.  Delete redundant lines for
	-mabi.  Add missing -mexplicit-relocs docs.
---
 gcc/doc/invoke.texi | 34 ++++++++++++++++++++--------------
 1 file changed, 20 insertions(+), 14 deletions(-)

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 44273284483..09f935eb194 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -979,7 +979,6 @@ See RS/6000 and PowerPC Options.
 
 @emph{RISC-V Options}
 @gccoptlist{-mbranch-cost=@var{N-instruction} @gol
--mmemcpy  -mno-memcpy @gol
 -mplt  -mno-plt @gol
 -mabi=@var{ABI-string} @gol
 -mfdiv  -mno-fdiv @gol
@@ -21772,18 +21771,12 @@ These command-line options are defined for RISC-V targets:
 @opindex mbranch-cost
 Set the cost of branches to roughly @var{n} instructions.
 
-@item -mmemcpy
-@itemx -mno-memcpy
-@opindex mmemcpy
-Don't optimize block moves.
-
 @item -mplt
 @itemx -mno-plt
 @opindex plt
-When generating PIC code, allow the use of PLTs. Ignored for non-PIC.
+When generating PIC code, do or don't allow the use of PLTs. Ignored for
+non-PIC.  The default is @option{-mplt}.
 
-@item -mabi=@var{ABI-string}
-@opindex mabi
 @item -mabi=@var{ABI-string}
 @opindex mabi
 Specify integer and floating-point calling convention.  @var{ABI-string}
@@ -21808,13 +21801,16 @@ registers are only 32 bits wide.
 @item -mfdiv
 @itemx -mno-fdiv
 @opindex mfdiv
-Use hardware floating-point divide and square root instructions.  This requires
-the F or D extensions for floating-point registers.
+Do or don't use hardware floating-point divide and square root instructions.
+This requires the F or D extensions for floating-point registers.  The default
+is to use them if the specified architecture has these instructions.
 
 @item -mdiv
 @itemx -mno-div
 @opindex mdiv
-Use hardware instructions for integer division.  This requires the M extension.
+Do or don't use hardware instructions for integer division.  This requires the
+M extension.  The default is to use them if the specified architecture has
+these instructions.
 
 @item -march=@var{ISA-string}
 @opindex march
@@ -21834,12 +21830,16 @@ Put global and static data smaller than @var{n} bytes into a special section
 @item -msave-restore
 @itemx -mno-save-restore
 @opindex msave-restore
-Use smaller but slower prologue and epilogue code.
+Do or don't use smaller but slower prologue and epilogue code that uses
+library function calls.  The default is to use fast inline prologues and
+epilogues.
 
 @item -mstrict-align
 @itemx -mno-strict-align
 @opindex mstrict-align
-Do not generate unaligned memory accesses.
+Do not or do generate unaligned memory accesses.  The default is set depending
+on whether the processor we are optimizing for supports fast unaligned access
+or not.
 
 @item -mcmodel=medlow
 @opindex mcmodel=medlow
@@ -21854,6 +21854,12 @@ Generate code for the medium-any code model. The program and its statically
 defined symbols must be within any single 2 GiB address range. Programs can be
 statically or dynamically linked.
 
+@item -mexplicit-relocs
+@itemx -mno-exlicit-relocs
+Use or do not use assembler relocation operators when dealing with symbolic
+addresses.  The alternative is to use assembler macros instead, which may
+limit optimization.
+
 @end table
 
 @node RL78 Options
-- 
2.14.1