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

[David Daney]

fanqifei wrote:

2010/1/13 Bingfeng Mei <b...@broadcom.com>:

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

Bingfeng

but insv is a standard pattern name.
the semantics of expression x= (x&0xFF00FFFF) | ((i<<16)&0x00FF0000);
is exactly what insv can do.
I all tried mips gcc cross compiler, and ins is also not generated.

You must be doing something wrong:

$ cat fanqifei.c
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;
}

$ mips64-linux-gcc -O3 -march=mips32r2 -mabi=32 -mno-abicalls -S fanqifei.c
$ cat fanqifei.s
        .file   1 "fanqifei.c"
        .section .mdebug.abi32
        .previous
        .gnu_attribute 4, 1
        .text
        .align  2
        .globl  foo
        .set    nomips16
        .ent    foo
        .type   foo, @function
foo:
        .frame  $sp,0,$31               # vars= 0, regs= 0/0, args= 0, gp= 0
        .mask   0x00000000,0
        .fmask  0x00000000,0
        .set    noreorder
        .set    nomacro
        lui     $3,%hi(x)
        lw      $2,%lo(x)($3)
        li      $5,2                    # 0x2
        move    $4,$2
        ins     $4,$5,12,2         #<<<<<<< Here it is.
        sw      $4,%lo(x)($3)
        j       $31
        ext     $2,$2,12,2

        .set    macro
        .set    reorder
        .end    foo
        .size   foo, .-foo

        .comm   x,4,4
        .ident  "GCC: (GNU) 4.5.0 20091223 (experimental) [trunk revision 
155414]"