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@xxxxxxxxx>:
> 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
