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Extend left-shift operator

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- Negative shift values are right-shift
- Optimize shift of 0 or more than 15
- Allow shifting symbols by complex relocation
This commit is contained in:
Stephen Casner
2021-02-15 00:10:24 -08:00
committed by Olaf Seibert
parent 93d7839ccf
commit 05fc94ce90
3 changed files with 119 additions and 89 deletions
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33
extree.c
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@@ -721,15 +721,44 @@ EX_TREE *evaluate(
left = evaluate(tp->data.child.left, undef);
right = evaluate(tp->data.child.right, undef);
/* Operate if both are literals */
if (left->type == EX_LIT && right->type == EX_LIT) {
res = new_ex_lit(left->data.lit << right->data.lit);
int shift = right->data.lit;
if (shift < 0)
res = new_ex_lit(left->data.lit >> -shift);
else
res = new_ex_lit(left->data.lit << shift);
free_tree(left);
free_tree(right);
break;
}
if (right->type == EX_LIT && /* Symbol shifted 0 == symbol */
right->data.lit == 0) {
res = left;
free_tree(right);
break;
}
if (right->type == EX_LIT && /* Anything shifted 16 == 0 */
((int)right->data.lit > 15 ||
(int)right->data.lit < -15)) {
res = new_ex_lit(0);
free_tree(left);
free_tree(right);
break;
}
if (right->type == EX_LIT) { /* Other shifts become * or / */
int shift = right->data.lit;
if (shift > 0)
res = new_ex_bin(EX_MUL, left, new_ex_lit(1 << shift));
else
res = new_ex_bin(EX_DIV, left, new_ex_lit(1 << -shift));
free_tree(right);
break;
}
/* Anything else returns verbatim */
res = new_ex_bin(EX_LSH, left, right);
}