Commit b9c18f56 authored by Aurelien Jarno's avatar Aurelien Jarno
Browse files

tcg: add a CONST flag to TCG helpers 



A const function only reads its arguments and does not use TCG
globals variables. Hence a call to such a function does not
save TCG globals variabes back to their canonical location.

Signed-off-by: default avatarAurelien Jarno <aurelien@aurel32.net>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@7008 c046a42c-6fe2-441c-8c8c-71466251a162
parent 34d5a9ff

tcg/tcg.c

+8 −4
Original line number Diff line number Diff line
@@ -1122,8 +1122,10 @@ static void tcg_liveness_analysis(TCGContext *s) 
                        dead_temps[arg] = 1;

                    }

                    

                    if (!(call_flags & TCG_CALL_CONST)) {

                        /* globals are live (they may be used by the call) */

                        memset(dead_temps, 0, s->nb_globals);

                    }



                    /* input args are live */

                    dead_iargs = 0;
@@ -1821,7 +1823,9 @@ static int tcg_reg_alloc_call(TCGContext *s, const TCGOpDef *def, 
    

    /* store globals and free associated registers (we assume the call

       can modify any global. */

    if (!(flags & TCG_CALL_CONST)) {

        save_globals(s, allocated_regs);

    }



    tcg_out_op(s, opc, &func_arg, &const_func_arg);

tcg/tcg.h

+4 −0
Original line number Diff line number Diff line
@@ -178,6 +178,10 @@ typedef int TCGv_i64; 
   and cannot raise exceptions. Hence a call to a pure function can be

   safely suppressed if the return value is not used. */

#define TCG_CALL_PURE           0x0010 

/* A const function only reads its arguments and does not use TCG

   globals variables. Hence a call to such a function does not

   save TCG globals variabes back to their canonical location. */

#define TCG_CALL_CONST          0x0020



/* used to align parameters */

#define TCG_CALL_DUMMY_TCGV     MAKE_TCGV_I32(-1)