rx.opt (mallow-string-insns): New option.

	* config/rx/rx.opt (mallow-string-insns): New option.
	* config/rx/rx.c (RX_BUILTIN_RMPA): Disable the use of this
	builtin if string instructions are denied.
	* config/rx/rx.h (TARGET_CPU_CPP_BUILTINS): Define
	__RX_ALLOW_STRING_INSNS__ or __RX_DISALLOW_STRING_INSNS__, as
	appropriate.
	(ASM_SPEC): Pass -mno-allow-string-insns on to the assembler.
	* config/rx/rx.md (movstr): Enable pattern only if string
	instructions are allowed.
	(rx_movstr, rx_strend, movmemsi, rx_movmem): Likewise.
	(cmpstrnsi, cmpstrsi, rx_cmpstrn, rmpa): Likewise.
	* config/rx/t-rx (MULTILIB_OPTIONS): Add mno-allow-string-insns.
	(MULTILIB_DIRNAMES): Add no-strings.
	* doc/invoke.texi: Document -mno-allow-string-insns.

	* gcc.target/rx/builtins.c: Disable RMPA test if string
	instructions are not allowed.

From-SVN: r222116

1 files changed, 22 insertions, 0 deletions

diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 520c2c5..18f69906 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -940,6 +940,7 @@ See RS/6000 and PowerPC Options.
 -mmax-constant-size=@gol
 -mint-register=@gol
 -mpid@gol
+-mallow-string-insns -mno-allow-string-insns@gol
 -mno-warn-multiple-fast-interrupts@gol
 -msave-acc-in-interrupts}
 
@@ -20057,6 +20058,27 @@ fast interrupt handler when it is compiling a file.  The default is to
 issue a warning for each extra fast interrupt handler found, as the RX
 only supports one such interrupt.
 
+@item -mallow-string-insns
+@itemx -mno-allow-string-insns
+@opindex mallow-string-insns
+@opindex mno-allow-string-insns
+Enables or disables the use of the string manipulation instructions
+@code{SMOVF}, @code{SCMPU}, @code{SMOVB}, @code{SMOVU}, @code{SUNTIL}
+@code{SWHILE} and also the @code{RMPA} instruction.  These
+instructions may prefetch data, which is not safe to do if accessing
+an I/O register.  (See section 12.2.7 of the RX62N Group User's Manual
+for more information).
+
+The default is to allow these instructions, but it is not possible for
+GCC to reliably detect all circumstances where a string instruction
+might be used to access an I/O register, so their use cannot be
+disabled automatically.  Instead it is reliant upon the programmer to
+use the @option{-mno-allow-string-insns} option if their program
+accesses I/O space.
+
+When the instructions are enabled GCC defines the C preprocessor
+symbol @code{__RX_ALLOW_STRING_INSNS__}, otherwise it defines the
+symbol @code{__RX_DISALLOW_STRING_INSNS__}.
 @end table
 
 @emph{Note:} The generic GCC command-line option @option{-ffixed-@var{reg}}