/* * (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 #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" #include "field_loc.h" #include "eval.h" #include "util_loc.h" #include "conversion.h" extern arith 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! */ void eval_field(struct expr *expr, int code) { int op = expr->OP_OPER; struct expr *leftop = expr->OP_LEFT; struct expr *rightop = expr->OP_RIGHT; struct field *fd = leftop->ex_type->tp_field; struct type *tp = leftop->ex_type->tp_up; arith tmpvar = 0; struct type *atype = ( tp->tp_unsigned && fd->fd_width >= 8 * (int)word_size) ? uword_type : word_type; /* First some assertions to be sure that the rest is legal */ ASSERT(atype->tp_size == 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); store_field(fd, tp->tp_unsigned, code, leftop, (arith) 0); } 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(word_size); } if (tp->tp_unsigned) { C_loc((arith)fd->fd_shift); C_sru(word_size); C_loc(fd->fd_mask); C_and(word_size); } else { arith sft = (int)word_size * 8 - fd->fd_width; C_loc(sft - fd->fd_shift); C_sli(word_size); C_loc(sft); C_sri(word_size); } if (code == TRUE && (op == POSTINCR || op == POSTDECR)) C_dup(word_size); 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); store_field(fd, atype->tp_unsigned, code == TRUE && op != POSTINCR && op != POSTDECR, leftop, 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 (tp->tp_unsigned == 0) { /* sign extension */ arith shift = (int)word_size * 8 - fd->fd_width; C_loc(shift); C_sli(word_size); C_loc(shift); C_sri(word_size); } conversion(atype, expr->ex_type); } } void store_field(struct field *fd, int uns, int code, struct expr *leftop, arith tmpvar) { C_loc(fd->fd_mask); C_and(word_size); if (code == TRUE) C_dup(word_size); C_loc((arith)fd->fd_shift); if (uns) C_slu(word_size); else C_sli(word_size); C_loc(~((fd->fd_mask << fd->fd_shift) | ~full_mask[(int)word_size])); if (leftop->ex_depth == 0) { /* simple case */ load_val(leftop, RVAL); C_and(word_size); C_ior(word_size); store_val(&(leftop->EX_VALUE), uns ? uword_type : word_type); } else { /* complex case */ if (! tmpvar) { tmpvar = NewLocal(pointer_size, pointer_align, reg_pointer, 0); EVAL(leftop, LVAL, TRUE, NO_LABEL, NO_LABEL); StoreLocal(tmpvar, pointer_size); } LoadLocal(tmpvar, pointer_size); C_loi(word_size); C_and(word_size); C_ior(word_size); LoadLocal(tmpvar, pointer_size); C_sti(word_size); FreeLocal(tmpvar); } } #endif /* NOBITFIELD */ #endif /* LINT */