CSC448: Phases: Introduce Three Address Code [7/8]

Write compound statements as

    { decls stats }

Write instances of DeclsStats as

    < decls | stats >

Write instances of DeclsStatsVariable as

    < decls | stats | Optional<v> >

If the exp must be present, then:

    < decls | stats | v >

The relevant functions are:

    transformStat (stat) = < decls | stats >
    transformExp (exp) = < decls | stats | Optional<v> >

To transform a statement, do a case analysis.

case StatCompound:

    transformStat (stat_0) = < decls_0 | stats_0 >
    ...
    transformStat (stat_n) = < decls_n | stats_n >
    -----------------------------------------------------
    transformStat (({decls stat_0 ... stat_n}))
      = < nil | { decls decls_0 ... decls_n stats_0 ... stats_m } >

case StatExp:

    transformExp (exp) = < decls | stats | ... >
    -----------------------------------------------------
    transformStat ((exp;)) = < decls | stats >

case StatGoto:

    -----------------------------------------------------
    transformStat ((goto l;)) = < nil | (goto l;) >

case StatIf:

    transformExp (exp) = < decls | stats | v >
    -----------------------------------------------------
    transformStat ((if (exp) goto l1; else goto l2;))
      = < decls | stats  (if (v) goto l1; else goto l2;) >

case StatReturn:

    -----------------------------------------------------
    transformStat ((return;)) = < nil | (return;) >

    transformExp (exp) = < decls | stats | v >
    -----------------------------------------------------------------
    transformStat ((return exp;)) = < decls | stats (return v;) >

case StatSkip:

    -----------------------------------------------------
    transformStat ((skip;)) = < nil | (skip;) >

To transform an expression, do a case analysis.

case ExpInt:

    -----------------------------------------------------
    transformExp (n) = < nil | nil | n >

case ExpVar:

    -----------------------------------------------------
    transformExp (x) = < nil | nil | x >

case ExpString:

    -----------------------------------------------------
    transformExp (("value"))
      = < (int[] x;) | (x = ("value");) | x >

case ExpNew:

    transformExp (exp) = < decls | stats | v >
    -----------------------------------------------------
    transformExp ((new T[exp];))
      = < decls (T[] x;) | stats (x = (new T[v]);) | x >

case ExpArrayAccess:

    transformExp (expA) = < decls1 | stats1 | v1 >
    transformExp (expI) = < decls2 | stats2 | v2 >
    ------------------------------------------------------------------------------
    transformExp ((expA[expI]) :: T)
      = < decls1 decls2 (T x;) | stats1 stats2 (x = (v1[v2]);) | x >

case ExpAssign:

    transformExp (expR) = < decls3 | stats3 | v3 >
    -----------------------------------------------------
    transformExp ((x = expR))
      = < decls3 | stats3 (x = v3;) | v3 >

    transformExp (expA) = < decls1 | stats1 | v1 >
    transformExp (expI) = < decls2 | stats2 | v2 >
    transformExp (expR) = < decls3 | stats3 | v3 >
    -------------------------------------------------------------------------------
    transformExp ((expA[expI] = expR))
      = < decls1 decls2 decls3 | stats1 stats2 stats3 (v1[v2] = v3;) | v3 >

case ExpUnOp:

    transformExp (exp) = < decls | stats | v >
    ------------------------------------------------------------
    transformExp ((unop exp) :: T)
      = < decls (T x;) | stats (x = (unop v);) | x >

case ExpBinOp:

    transformExp (expL)  = < decls1 | stats1 | v1 >
    transformExp (expR) = < decls2 | stats2 | v2 >
    ----------------------------------------------------------------------------------
    transformExp ((expL op expR) :: T)
      = < decls1 decls2 (T x;) | stats1 stats2 (x = (v1 op v2);) | x >

case ExpComma:

    transformExp (expL)  = < decls1 | stats1 | Optional<exp1> >
    transformExp (expR) = < decls2 | stats2 | Optional<exp2> >
    -----------------------------------------------------------
    transformExp ((expL , expR))
      = < decls1 decls2 | stats1 stats2 | Optional<exp2> >

case ExpFunCall:

    transformExp (exp1) = < decls1 | stats1 | v1 >
    ...
    transformExp (expn) = < declsn | statsn | vn >
    -------------------------------------------------------------------------
    transformExp ((f(exp1,...,expn)) :: void)
      = < decls1 ... declsn | stats1 ... statsn (f(v1,...,vn)) | nil >

    transformExp (exp1) = < decls1 | stats1 | v1 >
    ...
    transformExp (expn) = < declsn | statsn | vn >
    -------------------------------------------------------------------------
    transformExp ((f(exp1,...,expn)) :: T)
      = < decls1 ... declsn (T x;) | stats1 ... statsn (x = (f(v1,...,vn))) | x >