Your instruction is likely too specific to be picked up by GCC. You may use an intrinisc for it.
Bingfeng > -----Original Message----- > From: gcc-ow...@gcc.gnu.org [mailto:gcc-ow...@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 > >
