On Wed, 2010-08-25 at 00:55 -0400, Girisha SG wrote:
> > Thanks for your suggestion.
> > 
> > I have tried the same and now there is no warning during compilation but 
> > instead of crashing during Storing now it crashes loading itself :(.
> > 
> > Following is the error,
> > 505*stopped,reason="signal-received",signal-name="SIGSEGV",signal-meaning="
> > Segmentation fault",thread-id="1",frame={addr="0x00102148",func="NEON_Assembly
> > ",args=[{name="dest",value="<value optimized out>"},{name="src",value="0x1 <Address 0x1 out of bounds>"},{name="n",
value="400"
> > }],file="C:/ide-4.7-workspace/TestNeonOptimization/TestNeonOptimization.c",
> > fullname="C:/ide-4.7-workspace/TestNeonOptimization/TestNeonOptimization.c",
> > line="86"}
> > 
> > During runtime 'src' register should have the proper address but the value it 
> > had before crash was 0x1 !!!
> > 
> > Why all these are happening ? Is assembler not intelligent enough to take care
> >  of these things ?

Probably not. Assembler is a pretty literal translator from mnemonics to
machine code.

Compile your application with "-g -O0" this will leave your 'src' and
'dest' arguments visible to gdb, so you can check what is going on.

> 
> Also why assembler is using the same register for src and dest arrays ???

That I don't know.

I took a second look and it looks like your original %[src] without
extra square brackets was correct, but then I believe both (src) and
(data) should be (*src) and (*data), and constraint should be "m":

...
     "# load 8 pixels:\n\t"
     "vld3.8      {d16-d18}, %[src]!\n\t"
...
     "vst1.8      {d8}, %[dest]!\n\t"
...
/* Output */:[dest] "=m"/*"=&r"*/ (*dest), [n]/* Symbolic name */ "+r"/*
register constraint */ (n)/* C variable name*/
 /* Input */ :[src] "m" (*src)/*(&src)*/


But I can not guarantee this is all that is needed.


---
Aleksandar

Most likely because you haven't told it not to.  The constraint would
need to include "&".

        Unless an output operand has the `&' constraint modifier, GCC
        may
        allocate it in the same register as an unrelated input operand,
        on the assumption the inputs are consumed before the outputs are
        produced.  This assumption may be false if the assembler code
        actually consists of more than one instruction.  In such a case,
        use `&' for each output operand that may not overlap an input.
        *Note Modifiers::.

I'd suggest closely consulting

        http://gcc.gnu.org/onlinedocs/gcc-4.4.4/gcc/Constraints.html

Beware, though, that constraints are quite tricky and the documentation
is quite poor.  The only way to be absolutely certain of the meaning of
any particular constraint -- particularly any machine specific ones --
is to read the compiler source code.

Regards,
Neil

On Wed, 2010-08-25 at 00:55 -0400, Girisha SG wrote:
> > Thanks for your suggestion.
> > 
> > I have tried the same and now there is no warning during compilation but 
> > instead of crashing during Storing now it crashes loading itself :(.
> > 
> > Following is the error,
> > 505*stopped,reason="signal-received",signal-name="SIGSEGV",signal-meaning="
> > Segmentation fault",thread-id="1",frame={addr="0x00102148",func="NEON_Assembly
> > ",args=[{name="dest",value="<value optimized out>"},{name="src",value="0x1 <Address 0x1 out of bounds>"},{name="n",
value="400"
> > }],file="C:/ide-4.7-workspace/TestNeonOptimization/TestNeonOptimization.c",
> > fullname="C:/ide-4.7-workspace/TestNeonOptimization/TestNeonOptimization.c",
> > line="86"}
> > 
> > During runtime 'src' register should have the proper address but the value it 
> > had before crash was 0x1 !!!
> > 
> > Why all these are happening ? Is assembler not intelligent enough to take care
> >  of these things ?
> 
> Also why assembler is using the same register for src and dest arrays ???
> 
> 
> 
> 
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