/* * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands. * See the copyright notice in the ACK home directory, in the file "Copyright". */ /* $Id$ */ /* BITFIELD EXPRESSION EVALUATOR */ #include "lint.h" #ifndef LINT #include "nobitfield.h" #ifndef NOBITFIELD #include #include #include "debug.h" #include "arith.h" #include "type.h" #include "idf.h" #include "label.h" #include "code.h" #include "assert.h" #include "expr.h" #include "sizes.h" #include "align.h" #include "Lpars.h" #include "field.h" arith NewLocal(); /* util.c */ char *symbol2str(); /* symbol2str.c */ extern long full_mask[]; /* cstoper.c */ /* Eval_field() evaluates expressions involving bit fields. The various instructions are not yet optimised in the expression tree and are therefore dealt with in this function. The actions taken at any operation are described clearly by the code for this actions. Notes [1] the bitfields are packed in target machine integers! [2] op is either an assignment operator or an increment/ decrement operator [3] atype: the type in which the bitfield arithmetic is done; and in which bitfields are stored! */ eval_field(expr, code) struct expr *expr; int code; { int op = expr->OP_OPER; register struct expr *leftop = expr->OP_LEFT; register struct expr *rightop = expr->OP_RIGHT; register struct field *fd = leftop->ex_type->tp_field; struct type *tp = leftop->ex_type->tp_up; arith tmpvar; struct type *atype = tp->tp_unsigned ? uword_type : word_type; arith asize = atype->tp_size; /* First some assertions to be sure that the rest is legal */ ASSERT(asize == word_size); /* make sure that C_loc() is legal */ ASSERT(leftop->ex_type->tp_fund == FIELD); leftop->ex_type = atype; /* this is cheating but it works... */ if (op == '=') { /* F = E: f = ((E & mask)<ex_type); EVAL(rightop, RVAL, TRUE, NO_LABEL, NO_LABEL); conversion(tp, atype); C_loc(fd->fd_mask); C_and(asize); if (code == TRUE) C_dup(asize); C_loc((arith)fd->fd_shift); if (atype->tp_unsigned) C_slu(asize); else C_sli(asize); C_loc(~((fd->fd_mask << fd->fd_shift) | ~full_mask[asize])); if (leftop->ex_depth == 0) { /* simple case */ load_val(leftop, RVAL); C_and(asize); C_ior(asize); store_val(&(leftop->EX_VALUE), atype); } else { /* complex case */ tmpvar = NewLocal(pointer_size, pointer_align, reg_pointer, 0); EVAL(leftop, LVAL, TRUE, NO_LABEL, NO_LABEL); C_dup(pointer_size); StoreLocal(tmpvar, pointer_size); C_loi(asize); C_and(asize); C_ior(asize); LoadLocal(tmpvar, pointer_size); C_sti(asize); FreeLocal(tmpvar); } } else { /* treat ++F as F += 1 and --F as F -= 1 */ /* F op= e: f = (((((f>>shift)&mask) op e)&mask)<ex_depth == 0) /* simple case */ load_val(leftop, RVAL); else { /* complex case */ tmpvar = NewLocal(pointer_size, pointer_align, reg_pointer, 0); EVAL(leftop, LVAL, TRUE, NO_LABEL, NO_LABEL); C_dup(pointer_size); StoreLocal(tmpvar, pointer_size); C_loi(asize); } if (atype->tp_unsigned) { C_loc((arith)fd->fd_shift); C_sru(asize); C_loc(fd->fd_mask); C_and(asize); } else { arith bits_in_type = asize * 8; C_loc(bits_in_type - (fd->fd_width + fd->fd_shift)); C_sli(asize); C_loc(bits_in_type - fd->fd_width); C_sri(asize); } if (code == TRUE && (op == POSTINCR || op == POSTDECR)) C_dup(asize); conversion(atype, rightop->ex_type); EVAL(rightop, RVAL, TRUE, NO_LABEL, NO_LABEL); /* the 'op' operation: */ if (op == PLUSPLUS || op == POSTINCR) assop(rightop->ex_type, PLUSAB); else if (op == MINMIN || op == POSTDECR) assop(rightop->ex_type, MINAB); else assop(rightop->ex_type, op); conversion(rightop->ex_type, atype); C_loc(fd->fd_mask); C_and(asize); if (code == TRUE && op != POSTINCR && op != POSTDECR) C_dup(asize); C_loc((arith)fd->fd_shift); if (atype->tp_unsigned) C_slu(asize); else C_sli(asize); C_loc(~((fd->fd_mask << fd->fd_shift) | ~full_mask[asize])); if (leftop->ex_depth == 0) { load_val(leftop, RVAL); C_and(asize); C_ior(asize); store_val(&(leftop->EX_VALUE), atype); } else { LoadLocal(tmpvar, pointer_size); C_loi(asize); C_and(asize); C_ior(asize); LoadLocal(tmpvar, pointer_size); C_sti(asize); FreeLocal(tmpvar); } } if (code == TRUE) { /* Take care that the effective value stored in the bit field (i.e. the value that is got on retrieval) is on top of stack. */ if (atype->tp_unsigned == 0) { /* sign extension */ register arith shift = asize * 8 - fd->fd_width; C_loc(shift); C_sli(asize); C_loc(shift); C_sri(asize); } conversion(atype, expr->ex_type); } } #endif /* NOBITFIELD */ #endif /* LINT */