2004-09-07 David Daney <ddaney@avtrex.com>

	* config.gcc: Added support for --with-divide=[breaks|traps] for
	mips targets.
	* config/mips/mips.h (MASK_DIVIDE_BREAKS): New target_flags bit.
	(TARGET_DIVIDE_TRAPS): New macro.
	(TARGET_SWITCHES): Added -mdivide-traps and -mdivide-breaks.
	(OPTION_DEFAULT_SPECS): Added --with-divide= support.
	* config/mips/mips.c (mips_idiv_insns): Generate proper count on
	GENERATE_DIVIDE_TRAPS.
	(mips_output_division): Emit conditional trap if
	GENERATE_DIVIDE_TRAPS is set.
	* doc/install.texi: Document --with-divide.
	* doc/invoke.texi: Document -mdivide-traps and -mdivide-breaks.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@87153 138bc75d-0d04-0410-961f-82ee72b054a4

1 files changed, 22 insertions, 0 deletions

diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index dfad815d49a..01cbb47c25b 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -959,6 +959,18 @@ options and for @option{-mhard-float} or @option{-msoft-float}.  As with
 @option{--with-cpu}, which switches will be accepted and acceptable values
 of the arguments depend on the target.
 
+@item --with-divide=@var{type}
+Specify how the compiler should generate code for checking for
+division by zero.  This option is only supported on the MIPS target.
+The possibilities for @var{type} are:
+@table @code
+@item traps
+Division by zero checks use conditional traps (this is the default on
+systems that support conditional traps).
+@item breaks
+Division by zero checks use the break instruction.
+@end table
+
 @item --enable-altivec
 Specify that the target supports AltiVec vector enhancements.  This
 option will adjust the ABI for AltiVec enhancements, as well as generate
@@ -3201,6 +3213,16 @@ configure for @samp{mipsel-elf} as a workaround.  The
 @samp{mips*-*-linux*} target continues to use the MIPS II routines.  More
 work on this is expected in future releases.
 
+MIPS systems check for division by zero (unless
+@option{-mno-check-zero-division} is passed to the compiler) by
+generating either a conditional trap or a break instruction.  Using
+trap results in smaller code, but is only supported on MIPS II and
+later.  Also, some versions of the Linux kernel have a bug that
+prevents trap from generating the proper signal (SIGFPE).  To enable
+the use of break, use the @option{--with-divide=breaks}
+@command{configure} option when configuring GCC.  The default is to
+use traps on systems that support them.
+
 Cross-compilers for the Mips as target using the Mips assembler
 currently do not work, because the auxiliary programs
 @file{mips-tdump.c} and @file{mips-tfile.c} can't be compiled on