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ceriel
181
lang/cem/cemcom.ansi/field.c
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181
lang/cem/cemcom.ansi/field.c
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/*
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* (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
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* See the copyright notice in the ACK home directory, in the file "Copyright".
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*/
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/* $Header$ */
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/* BITFIELD EXPRESSION EVALUATOR */
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#include "lint.h"
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#ifndef LINT
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#include "nobitfield.h"
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#ifndef NOBITFIELD
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#include <em.h>
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#include <em_reg.h>
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#include "debug.h"
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#include "arith.h"
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#include "type.h"
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#include "idf.h"
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#include "label.h"
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#include "code.h"
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#include "assert.h"
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#include "expr.h"
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#include "sizes.h"
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#include "align.h"
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#include "Lpars.h"
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#include "field.h"
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arith NewLocal(); /* util.c */
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char *symbol2str(); /* symbol2str.c */
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/* Eval_field() evaluates expressions involving bit fields.
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The various instructions are not yet optimised in the expression
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tree and are therefore dealt with in this function.
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The actions taken at any operation are described clearly by the
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code for this actions.
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Notes
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[1] the bitfields are packed in target machine integers!
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[2] op is either an assignment operator or an increment/
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decrement operator
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[3] atype: the type in which the bitfield arithmetic is done;
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and in which bitfields are stored!
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*/
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eval_field(expr, code)
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struct expr *expr;
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int code;
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{
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int op = expr->OP_OPER;
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register struct expr *leftop = expr->OP_LEFT;
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register struct expr *rightop = expr->OP_RIGHT;
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register struct field *fd = leftop->ex_type->tp_field;
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struct type *tp = leftop->ex_type->tp_up;
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arith tmpvar;
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struct type *atype = tp->tp_unsigned ? uword_type : word_type;
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arith asize = atype->tp_size;
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/* First some assertions to be sure that the rest is legal */
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ASSERT(asize == word_size); /* make sure that C_loc() is legal */
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ASSERT(leftop->ex_type->tp_fund == FIELD);
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leftop->ex_type = atype; /* this is cheating but it works... */
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if (op == '=') {
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/* F = E: f = ((E & mask)<<shift) | (~(mask<<shift) & f) */
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ASSERT(tp == rightop->ex_type);
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EVAL(rightop, RVAL, TRUE, NO_LABEL, NO_LABEL);
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conversion(tp, atype);
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C_loc(fd->fd_mask);
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C_and(asize);
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if (code == TRUE)
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C_dup(asize);
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C_loc((arith)fd->fd_shift);
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if (atype->tp_unsigned)
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C_slu(asize);
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else
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C_sli(asize);
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C_loc(~((fd->fd_mask << fd->fd_shift) | (~0 << (8 * asize))));
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if (leftop->ex_depth == 0) { /* simple case */
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load_val(leftop, RVAL);
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C_and(asize);
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C_ior(asize);
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store_val(&(leftop->EX_VALUE), atype);
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}
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else { /* complex case */
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tmpvar = NewLocal(pointer_size, pointer_align,
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reg_pointer, 0);
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EVAL(leftop, LVAL, TRUE, NO_LABEL, NO_LABEL);
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C_dup(pointer_size);
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StoreLocal(tmpvar, pointer_size);
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C_loi(asize);
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C_and(asize);
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C_ior(asize);
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LoadLocal(tmpvar, pointer_size);
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C_sti(asize);
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FreeLocal(tmpvar);
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}
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}
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else { /* treat ++F as F += 1 and --F as F -= 1 */
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/* F op= e: f = (((((f>>shift)&mask) op e)&mask)<<shift)|
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(f&~(mask<<shift))
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*/
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if (leftop->ex_depth == 0) /* simple case */
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load_val(leftop, RVAL);
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else { /* complex case */
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tmpvar = NewLocal(pointer_size, pointer_align,
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reg_pointer, 0);
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EVAL(leftop, LVAL, TRUE, NO_LABEL, NO_LABEL);
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C_dup(pointer_size);
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StoreLocal(tmpvar, pointer_size);
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C_loi(asize);
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}
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if (atype->tp_unsigned) {
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C_loc((arith)fd->fd_shift);
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C_sru(asize);
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C_loc(fd->fd_mask);
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C_and(asize);
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}
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else {
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arith bits_in_type = asize * 8;
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C_loc(bits_in_type - (fd->fd_width + fd->fd_shift));
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C_sli(asize);
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C_loc(bits_in_type - fd->fd_width);
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C_sri(asize);
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}
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if (code == TRUE && (op == POSTINCR || op == POSTDECR))
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C_dup(asize);
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conversion(atype, rightop->ex_type);
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EVAL(rightop, RVAL, TRUE, NO_LABEL, NO_LABEL);
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/* the 'op' operation: */
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if (op == PLUSPLUS || op == POSTINCR)
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assop(rightop->ex_type, PLUSAB);
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else
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if (op == MINMIN || op == POSTDECR)
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assop(rightop->ex_type, MINAB);
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else
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assop(rightop->ex_type, op);
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conversion(rightop->ex_type, atype);
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C_loc(fd->fd_mask);
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C_and(asize);
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if (code == TRUE && op != POSTINCR && op != POSTDECR)
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C_dup(asize);
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C_loc((arith)fd->fd_shift);
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if (atype->tp_unsigned)
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C_slu(asize);
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else
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C_sli(asize);
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C_loc(~((fd->fd_mask << fd->fd_shift) | (~0 << (8 * asize))));
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if (leftop->ex_depth == 0) {
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load_val(leftop, RVAL);
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C_and(asize);
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C_ior(asize);
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store_val(&(leftop->EX_VALUE), atype);
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}
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else {
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LoadLocal(tmpvar, pointer_size);
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C_loi(asize);
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C_and(asize);
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C_ior(asize);
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LoadLocal(tmpvar, pointer_size);
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C_sti(asize);
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FreeLocal(tmpvar);
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}
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}
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if (code == TRUE) {
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/* Take care that the effective value stored in
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the bit field (i.e. the value that is got on
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retrieval) is on top of stack.
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*/
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if (atype->tp_unsigned == 0) { /* sign extension */
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register arith shift = asize * 8 - fd->fd_width;
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C_loc(shift);
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C_sli(asize);
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C_loc(shift);
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C_sri(asize);
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}
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conversion(atype, expr->ex_type);
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}
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}
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#endif NOBITFIELD
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#endif LINT
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