"Thomas A.M. Bernard" <[EMAIL PROTECTED]> writes: > Ian Lance Taylor wrote: >> "Thomas A.M. Bernard" <[EMAIL PROTECTED]> writes: >> >> >>> I guess I am missing something here. I've tried the following as Paolo >>> suggested, >>> >>> (define_insn "setallocate" >>> [(unspec_volatile:DI [(match_operand:DI 0 "general_operand" "r")] >>> UNSPEC_ALLOCATE)] >>> "" >>> "allocate %0\t\t#TCB_INSTRUCTIONS" [(set_attr "type" "multi")]) >>> >>> When flag -O0 is on, everything's fine. But when flag -O1 is engaged, >>> the instruction is still omitted. Something missing ? >>> >> >> The only that gcc will remove an unspec_volatile instruction is if it >> is on a code path which is never executed. >> Look at the RTL dump files (from, e.g., -fdump-rtl-all), see where >> it >> is disappearing, and why. >> > With this pattern for setallocate, when the flag -O1 is engaged, the > instruction is already omitted just at the expansion. As Ian > mentioned, I suspect the problem comes from the fact that the compiler > thinks this code path won't be executed. I presume this should be done > at the CFG level. I added in CFG a "node" which describes > setallocate' Any clue to say explicitly this will be executed in any > case ?
The conventional way to get a special purpose instruction through the tree code is to use a builtin function. For example, look at the calls to __builtin_XXX in config/i386/mmintrin.h (a header file included by target programs) and the associated code in config/i386/i386.c. Ian
