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Handle subtractions between labels

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This commit is contained in:
ISSOtm
2020-01-20 23:07:31 +01:00
parent b4a73f33ce
commit 52d62c6b21
1 changed files with 27 additions and 1 deletions
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28
src/asm/rpn.c
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@@ -274,6 +274,28 @@ static int32_t shift(int32_t shiftee, int32_t amount)
}
}
static struct sSymbol const *symbolOf(struct Expression const *expr)
{
/* If an expression starts with a symbol ref... */
if (!expr->tRPN || expr->tRPN[0] != RPN_SYM || expr->nRPNPatchSize != 5)
return NULL;
return sym_FindSymbol((char *)expr->tRPN + 1);
}
static bool isDiffConstant(struct Expression const *src1,
struct Expression const *src2)
{
/* Check if both expressions only refer to a single symbol */
struct sSymbol const *symbol1 = symbolOf(src1);
struct sSymbol const *symbol2 = symbolOf(src2);
if (!symbol1 || !symbol2
|| symbol1->type != SYM_LABEL || symbol2->type != SYM_LABEL)
return false;
return symbol1->pSection == symbol2->pSection;
}
void rpn_BinaryOp(enum RPNCommand op, struct Expression *expr,
const struct Expression *src1, const struct Expression *src2)
{
@@ -383,8 +405,12 @@ void rpn_BinaryOp(enum RPNCommand op, struct Expression *expr,
fatalerror("%d is no binary operator", op);
}
/* TODO: under some conditions, the expression will still be known */
} else if (op == RPN_SUB && isDiffConstant(src1, src2)) {
struct sSymbol const *symbol1 = symbolOf(src1);
struct sSymbol const *symbol2 = symbolOf(src2);
expr->nVal = symbol1->nValue - symbol2->nValue;
expr->isKnown = true;
} else {
/* If it's not known, start computing the RPN expression */