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re PR target/51345 ([avr] Devices with 8-bit SP need their own multilib(s)) 

PR target/51345
	* config/avr/avr.opt (-msp8): Document it.
	* doc/invoke.texi (AVR Options): Ditto.  And document related
	built-in macros.

From-SVN: r188070
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Georg-Johann Lay 2012-05-31 17:32:42 +00:00 committed by Georg-Johann Lay
parent bdd5dc28aa
commit 621dfb1e58
3 changed files with 48 additions and 6 deletions
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7
gcc/ChangeLog
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@ -1,3 +1,10 @@
2012-05-31 Georg-Johann Lay <avr@gjlay.de>
PR target/51345
* config/avr/avr.opt (-msp8): Document it.
* doc/invoke.texi (AVR Options): Ditto. And document related
built-in macros.
2012-05-31 Diego Novillo <dnovillo@google.com>
* configure.ac (CXX_FOR_BUILD): Define and substitute.

3
gcc/config/avr/avr.opt
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@ -76,4 +76,5 @@ When accessing RAM, use X as imposed by the hardware, i.e. just use pre-decremen
;; For rationale behind -msp8 see explanation in avr.h.
msp8
Target Report RejectNegative Undocumented Var(avr_sp8) Init(0)
Target Report RejectNegative Var(avr_sp8) Init(0)
The device has no SPH special function register. This option will be overridden by the compiler driver with the correct setting if presence/absence of SPH can be deduced from -mmcu=MCU.

44
gcc/doc/invoke.texi
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@ -11094,6 +11094,9 @@ known before code is located. Therefore, the assembler code generated by the
compiler is the same, but the instructions in the executable may
differ from instructions in the assembler code.
Relaxing must be turned on if linker stubs are needed, see the
section on @code{EIND} and linker stubs below.
@item -mshort-calls
@opindex mshort-calls
Use @code{RCALL}/@code{RJMP} instructions even on devices with
@ -11101,6 +11104,21 @@ Use @code{RCALL}/@code{RJMP} instructions even on devices with
have the @code{CALL} and @code{JMP} instructions.
See also the @code{-mrelax} command line option.
@item -msp8
@opindex msp8
Treat the stack pointer register as an 8-bit register,
i.e.@: assume the high byte of the stack pointer is zero.
In general, you don't need to set this option by hand.
This option is used internally by the compiler to select and
build multilibs for architectures @code{avr2} and @code{avr25}.
These architectures mix devices with and without @code{SPH}.
For any setting other than @code{-mmcu=avr2} or @code{-mmcu=avr25}
the compiler driver will add or remove this option from the compiler
proper's command line, because the compiler then knows if the device
or architecture has an 8-bit stack pointer and thus no @code{SPH}
register or not.
@item -mstrict-X
@opindex mstrict-X
Use address register @code{X} in a way proposed by the hardware. This means
@ -11162,6 +11180,13 @@ generates @emph{stubs}. Stubs are jump pads sometimes also called
@emph{trampolines}. Thus, the indirect call/jump jumps to such a stub.
The stub contains a direct jump to the desired address.
@item
Linker relaxation must be turned on so that the linker will generate
the stubs correctly an all situaltion. See the compiler option
@code{-mrelax} and the linler option @code{--relax}.
There are corner cases where the linker is supposed to generate stubs
but aborts without relaxation and without a helpful error message.
@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
@ -11189,8 +11214,8 @@ static void
__attribute__((section(".init3"),naked,used,no_instrument_function))
init3_set_eind (void)
@{
__asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
"out %i0,r24" :: "n" (&EIND) : "r24","memory");
__asm volatile ("ldi r24,pm_hh8(__trampolines_start)\n\t"
"out %i0,r24" :: "n" (&EIND) : "r24","memory");
@}
@end example
@ -11332,8 +11357,8 @@ The device has the @code{MOVW} instruction to perform 16-bit
register-register moves.
@item __AVR_HAVE_LPMX__
The device has the @code{LPM R@var{n},Z} and @code{LPM
R@var{n},Z+} instructions.
The device has the @code{LPM R@var{n},Z} and
@code{LPM R@var{n},Z+} instructions.
@item __AVR_HAVE_MUL__
The device has a hardware multiplier.
@ -11356,9 +11381,18 @@ with up to 128@tie{}KiB of program memory.
@item __AVR_HAVE_8BIT_SP__
@item __AVR_HAVE_16BIT_SP__
The stack pointer (SP) is respectively 8 or 16 bits wide.
The stack pointer (SP) register is treated as 8-bit respectively
16-bit register by the compiler.
The definition of these macros is affected by @code{-mtiny-stack}.
@item __AVR_HAVE_SPH__
@item __AVR_SP8__
The device has the SPH (high part of stack pointer) special function
register or has an 8-bit stack pointer, respectively.
The definition of these macros is affected by @code{-mmcu=} and
in the cases of @code{-mmcu=avr2} and @code{-mmcu=avr25} also
by @code{-msp8}.
@item __AVR_HAVE_RAMPD__
@item __AVR_HAVE_RAMPX__
@item __AVR_HAVE_RAMPY__