Re: ins instruction is not produced in the assembly code (mips32r2)

[fanqifei <fanqifei at gmail dot com>]

Is there anyone can help?
I am curious about how the insv pattern can be used in the compiling process.
Otherwise, I have to write inline assembly code.
Thanks very much!

2009/12/16 fanqifei <fanqifei@gmail.com>:
> Hello,
> I am tring to compile a small c file using gcc4.1.2.
> The source code:
> 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;
> }
>
> the command: mipsel-linux-gcc -mips32r2 -O2 -c -Wall foo.c -o foo.o
>
> The corresponding disassembly code:
> foo.o:???? file format elf32-tradlittlemips
> Disassembly of section .text:
> 00000000 <foo>:
> ?? 0:?? 3c1c0000??? lui gp,0x0
> ?? 4:?? 279c0000??? addiu?? gp,gp,0
> ?? 8:?? 0399e021??? addu??? gp,gp,t9
> ?? c:?? 8f850000??? lw? a1,0(gp)
> ? 10:?? 3c03fff3??? lui v1,0xfff3
> ? 14:?? 3463ffff??? ori v1,v1,0xffff
> ? 18:?? 8ca20000??? lw? v0,0(a1)
> ? 1c:?? 3c040008??? lui a0,0x8
> ? 20:?? 00431824??? and v1,v0,v1
> ? 24:?? 00641825??? or? v1,v1,a0
> ? 28:?? 7c420c80??? ext v0,v0,0x12,0x2
> ? 2c:?? 03e00008??? jr? ra
> ? 30:?? aca30000??? sw? v1,0(a1)
> The statement x.b=2 can be simply translated to lb and ins instructions( ins
> is in mips32r2).
>
> I wonder how ins instrution can be produced.
> More specifically,?how can?gcc generates the insv pattern in RTL?
> Is it related to the coding style -- using bit filed or logical
> operations(shift, and ...)?
> Thanks.
> Qifei
>
>



-- 
        Qifei Fan