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- /*
- * (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 <em.h>
- #include <em_reg.h>
- #include "debug.h"
- #include <flt_arith.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"
- #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)<<shift) | (~(mask<<shift) & f) */
- ASSERT(tp == rightop->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)<<shift)|
- (f&~(mask<<shift))
- */
- if (leftop->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 */
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