MSP430 in gcc4.9 ... enable interrupts?

2014-02-14 Thread Brian Drummond 
I have built a crosscompiler for the MSP430, using a gcc4.9 snapshot
(gcc-4.9-20140112) and the compiler seems OK and builds a simple
"blinky" LED flashing example.

But my slightly larger example, originally built using Peter Bigot's
mspgcc backend, no longer compiles ... 

mspgcc had a number of intrinsic functions, such as __nop(), __eint()
and __dint() respectively. Calling these would execute a nop, enable and
disable interrupts respectively. 

Others such as __bis_status_register(), __bic_status_register() would
manipulate system status, low power modes etc.

Now in the MSP430 port for gcc4.9, these intrinsic functions have gone. 

Perusing the config/msp430 source files, e.g. config/msp430/msp430.md I
can see evidence that the _functionality_ is still there, e.g.

(define_insn "enable_interrupts"
  [(unspec_volatile [(const_int 0)] UNS_EINT)]
  ""
  "EINT"
  )
...
(define_insn "bis_SR"
  [(unspec_volatile [(match_operand 0 "nonmemory_operand" "ir")]
UNS_BIS_SR)]
  ""
  "BIS.W\t%0, %O0(SP)"
  )

... but how do I access it? In other words, what C code fragment would
cause the "enable_interrupts" instruction to be emitted, and generate
"EINT" in the assembler or object output?

- Brian

Re: gnattools cannot be built for freestanding/bare metal environment without hacking up the build machinery

2014-02-14 Thread Brian Drummond 
Luke A. Guest  archeia.com> writes:

> 
> Hi,
> 
> I've been over this before and have got nowhere with it. 

> Say you want to build an Ada compiler for embedded work, ...
> You can build it with "make all-gcc" and install with "make install-gcc"
> ...
> But what about the gnattools? Not buildable. A message in the ml
> archives states to build them with "make -C gcc gnattools," but this
> fails:
> ...
> You can't disable libada using the command line as that also disables
> gnattools - I don't know the reason for requiring this behaviour.
> 

Revisiting the MSP430 as it's now an official gcc target, this is still a
problem here too, so there are at least 3 targets for which it's a problem.

Looking at http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19959
and comparing comments #6 and #14, perhaps this command should be 
"make -C gcc gnattools-cross" ? I'll try to do a clean build and test this
today.

But it would be better if the build "just worked" so at

> if test "${ENABLE_LIBADA}" != "yes" ; then
>   noconfigdirs="$noconfigdirs"
> fi
we need a better test here (also checking for a crosscompiler build).

> I think that we need a configure flag to disable libada and not
> gnattools for these bare board targets.

Following comment #15 in bug 19959, perhaps it's time to open a bug against
--disable-libada.

- Brian

Re: MSP430 in gcc4.9 ... enable interrupts?

2014-02-14 Thread Brian Drummond 
On Fri, 2014-02-14 at 14:17 -0500, DJ Delorie wrote:
> The constructs in the *.md files are for the compiler's internal use
> (i.e. there are function attributes that trigger those).  You don't
> need compiler support for these opcodes at the user level; the right
> way is to implement those builtins as inline assembler 

> static inline __attribute__((always_inline))
> void __nop()
> {
>   asm volatile ("NOP");
> }

Thanks for the answer. I thought I was missing something, but apparently
not. Now it's clear that inline assembler is the official way, I can
adapt that approach to my situation. 

- Brian