-iwithprefixbefore @var{dir} -isystem @var{dir} @gol
-imultilib @var{dir} -isysroot @var{dir} @gol
-M -MM -MF -MG -MP -MQ -MT -nostdinc @gol
--P -fworking-directory -remap @gol
--trigraphs -undef -U@var{macro} -Wp,@var{option} @gol
--Xpreprocessor @var{option}}
+-P -fdebug-cpp -ftrack-macro-expansion -fworking-directory @gol
+-remap -trigraphs -undef -U@var{macro} @gol
+-Wp,@var{option} -Xpreprocessor @var{option}}
@item Assembler Option
@xref{Assembler Options,,Passing Options to the Assembler}.
@emph{AVR Options}
@gccoptlist{-mmcu=@var{mcu} -mno-interrupts @gol
--mcall-prologues -mtiny-stack -mint8}
+-mcall-prologues -mtiny-stack -mint8 -mstrict-X}
@emph{Blackfin Options}
@gccoptlist{-mcpu=@var{cpu}@r{[}-@var{sirevision}@r{]} @gol
-mfaster-structs -mno-faster-structs -mflat -mno-flat @gol
-mfpu -mno-fpu -mhard-float -msoft-float @gol
-mhard-quad-float -msoft-quad-float @gol
--mlittle-endian @gol
-mstack-bias -mno-stack-bias @gol
-munaligned-doubles -mno-unaligned-doubles @gol
-mv8plus -mno-v8plus -mvis -mno-vis @gol
int i = @{ 2.2 @}; // error: narrowing from double to int
@end smallexample
-This flag can be useful for compiling valid C++98 code in C++0x mode.
+This flag can be useful for compiling valid C++98 code in C++0x mode
@item -Wnoexcept @r{(C++ and Objective-C++ only)}
@opindex Wnoexcept
warning if the unused arguments are all pointers, since the Single
Unix Specification says that such unused arguments are allowed.
-@item -Wno-format-zero-length @r{(C and Objective-C only)}
+@item -Wno-format-zero-length
@opindex Wno-format-zero-length
@opindex Wformat-zero-length
If @option{-Wformat} is specified, do not warn about zero-length formats.
@option{-Wformat}. Currently equivalent to @samp{-Wformat
-Wformat-nonliteral -Wformat-security -Wformat-y2k}.
-@item -Wnonnull @r{(C and Objective-C only)}
+@item -Wnonnull
@opindex Wnonnull
@opindex Wno-nonnull
Warn about passing a null pointer for arguments marked as
low, value expressions that are available and could be represented in
debug information may end up not being used; setting this higher may
enable the compiler to find more complex debug expressions, but compile
-time may grow exponentially, and even then, it may fail to find more
-usable expressions. The default is 10.
+time and memory use may grow. The default is 12.
@item min-nondebug-insn-uid
Use uids starting at this parameter for nondebug insns. The range below
@samp{fa526}, @samp{fa626},
@samp{fa606te}, @samp{fa626te}, @samp{fmp626}, @samp{fa726te}.
+
@option{-mcpu=generic-@var{arch}} is also permissible, and is
equivalent to @option{-march=@var{arch} -mtune=generic-@var{arch}}.
See @option{-mtune} for more information.
+@option{-mcpu=native} causes the compiler to auto-detect the CPU
+of the build computer. At present, this feature is only supported on
+Linux, and not all architectures are recognised. If the auto-detect is
+unsuccessful the option has no effect.
+
@item -mtune=@var{name}
@opindex mtune
This option is very similar to the @option{-mcpu=} option, except that
range, and avoiding performance pitfalls of other CPUs. The effects of
this option may change in future GCC versions as CPU models come and go.
+@option{-mtune=native} causes the compiler to auto-detect the CPU
+of the build computer. At present, this feature is only supported on
+Linux, and not all architectures are recognised. If the auto-detect is
+unsuccessful the option has no effect.
+
@item -march=@var{name}
@opindex march
This specifies the name of the target ARM architecture. GCC uses this
@samp{armv7}, @samp{armv7-a}, @samp{armv7-r}, @samp{armv7-m},
@samp{iwmmxt}, @samp{iwmmxt2}, @samp{ep9312}.
+@option{-march=native} causes the compiler to auto-detect the architecture
+of the build computer. At present, this feature is only supported on
+Linux, and not all architectures are recognised. If the auto-detect is
+unsuccessful the option has no effect.
+
@item -mfpu=@var{name}
@itemx -mfpe=@var{number}
@itemx -mfp=@var{number}
and long long will be 4 bytes. Please note that this option does not
comply to the C standards, but it will provide you with smaller code
size.
+
+@item -mstrict-X
+@opindex mstrict-X
+Use register @code{X} in a way proposed by the hardware. This means
+that @code{X} will only be used in indirect, post-increment or
+pre-decrement addressing.
+
+Without this option, the @code{X} register may be used in the same way
+as @code{Y} or @code{Z} which then is emulated by additional
+instructions.
+For example, loading a value with @code{X+const} addressing with a
+small @code{const <= 63} to a register @var{Rn} will be printed as
+@example
+adiw r26, const
+ld @var{Rn}, X
+sbiw r26, const
+@end example
@end table
+@subsubsection @code{EIND} and Devices with more than 128k Bytes of Flash
+
+Pointers in the implementation are 16 bits wide.
+The address of a function or label is represented as word address so
+that indirect jumps and calls can address any code address in the
+range of 64k words.
+
+In order to faciliate indirect jump on devices with more than 128k
+bytes of program memory space, there is a special function register called
+@code{EIND} that serves as most significant part of the target address
+when @code{EICALL} or @code{EIJMP} instructions are used.
+
+Indirect jumps and calls on these devices are handled as follows and
+are subject to some limitations:
+
+@itemize @bullet
+
+@item
+The compiler never sets @code{EIND}.
+
+@item
+The startup code from libgcc never sets @code{EIND}.
+Notice that startup code is a blend of code from libgcc and avr-libc.
+For the impact of avr-libc on @code{EIND}, see the
+@w{@uref{http://nongnu.org/avr-libc/user-manual,avr-libc user manual}}.
+
+@item
+The compiler uses @code{EIND} implicitely in @code{EICALL}/@code{EIJMP}
+instructions or might read @code{EIND} directly.
+
+@item
+The compiler assumes that @code{EIND} never changes during the startup
+code or run of the application. In particular, @code{EIND} is not
+saved/restored in function or interrupt service routine
+prologue/epilogue.
+
+@item
+It is legitimate for user-specific startup code to set up @code{EIND}
+early, for example by means of initialization code located in
+section @code{.init3}, and thus prior to general startup code that
+initializes RAM and calls constructors.
+
+@item
+For indirect calls to functions and computed goto, the linker will
+generate @emph{stubs}. Stubs are jump pads sometimes also called
+@emph{trampolines}. Thus, the indirect call/jump will jump to such a stub.
+The stub contains a direct jump to the desired address.
+
+@item
+Stubs will be generated automatically by the linker if
+the following two conditions are met:
+@itemize @minus
+
+@item The address of a label is taken by means of the @code{gs} modifier
+(short for @emph{generate stubs}) like so:
+@example
+LDI r24, lo8(gs(@var{func}))
+LDI r25, hi8(gs(@var{func}))
+@end example
+@item The final location of that label is in a code segment
+@emph{outside} the segment where the stubs are located.
+@end itemize
+
+@item
+The compiler will emit such @code{gs} modifiers for code labels in the
+following situations:
+@itemize @minus
+@item Taking address of a function or code label.
+@item Computed goto.
+@item If prologue-save function is used, see @option{-mcall-prologues}
+command line option.
+@item Switch/case dispatch tables. If you do not want such dispatch
+tables you can specify the @option{-fno-jump-tables} command line option.
+@item C and C++ constructors/destructors called during startup/shutdown.
+@item If the tools hit a @code{gs()} modifier explained above.
+@end itemize
+
+@item
+The default linker script is arranged for code with @code{EIND = 0}.
+If code is supposed to work for a setup with @code{EIND != 0}, a custom
+linker script has to be used in order to place the sections whose
+name start with @code{.trampolines} into the segment where @code{EIND}
+points to.
+
+@item
+Jumping to non-symbolic addresses like so is @emph{not} supported:
+
+@example
+int main (void)
+@{
+ /* Call function at word address 0x2 */
+ return ((int(*)(void)) 0x2)();
+@}
+@end example
+
+Instead, a stub has to be set up:
+
+@example
+int main (void)
+@{
+ extern int func_4 (void);
+
+ /* Call function at byte address 0x4 */
+ return func_4();
+@}
+@end example
+
+and the application be linked with @code{-Wl,--defsym,func_4=0x4}.
+Alternatively, @code{func_4} can be defined in the linker script.
+@end itemize
+
@node Blackfin Options
@subsection Blackfin Options
@cindex Blackfin Options
of the non-reciprocal instruction, the precision of the sequence can be
decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).
-Note that GCC implements 1.0f/sqrtf(x) in terms of RSQRTSS (or RSQRTPS)
+Note that GCC implements @code{1.0f/sqrtf(@var{x})} in terms of RSQRTSS
+(or RSQRTPS) already with @option{-ffast-math} (or the above option
+combination), and doesn't need @option{-mrecip}.
+
+Also note that GCC emits the above sequence with additional Newton-Raphson step
+for vectorized single float division and vectorized @code{sqrtf(@var{x})}
already with @option{-ffast-math} (or the above option combination), and
doesn't need @option{-mrecip}.
on SPARC-V9 processors in 64-bit environments:
@table @gcctabopt
-@item -mlittle-endian
-@opindex mlittle-endian
-Generate code for a processor running in little-endian mode. It is only
-available for a few configurations and most notably not on Solaris and Linux.
-
@item -m32
@itemx -m64
@opindex m32
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