GCC-How does the coding style affect the insv pattern recognization?

[Bingfeng Mei]

Your instruction is likely too specific to be picked up by GCC. 
You may use an intrinisc for it. 

Bingfeng 

> -----Original Message-----
> From: gcc-owner@gcc.gnu.org [mailto:gcc-owner@gcc.gnu.org] On 
> Behalf Of fanqifei
> Sent: 12 January 2010 12:50
> To: gcc@gcc.gnu.org
> Subject: GCC-How does the coding style affect the insv 
> pattern recognization?
> 
> Hi,
>     I am working on a micro controller and trying to port 
> gcc(4.3.2) for it.
>     There is insv instruction in our micro controller and I have add
> define_insn to machine description file.
>     However, the insv instruction can only be generated when the code
> is written like below.  If the code is written using logical shift and
>     or operators, the insv instruction will not be generated.
>     For the statement: x= (x&0xFF00FFFF) | ((i<<16)&0x00FF0000);
>     6 RTL instructions are generated after combine pass and 8
> instructions are generated in the assembly file.
>     Paolo Bonzini said that insv instruction might be synthesized
> later by combine. But combine only works on at most 3 instructions and
> insv is not generated in such case.
>     So exactly when will the insv pattern be recognized and how does
> the coding style affect it?
>     Is there any open bug report about this?
> 
> struct test_foo {
> unsigned int a:18;
> unsigned int b:2;
> unsigned int c:12;
> };
> 
> struct test_foo x;
> 
> unsigned int foo()
> {
> unsigned int a=x.b;
> x.b=2;
> return a;
> }
> 
> Thanks!
> fanqifei
> 
>