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X && 0 and X & 0 are constant 0; X || 1 is constant 1 (#1399)

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Fixes #977
This commit is contained in:
Sylvie
2024-06-13 11:09:39 -04:00
committed by GitHub
parent c5c6cc9794
commit dfec7111e2
6 changed files with 65 additions and 2 deletions
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14
src/asm/rpn.cpp
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@@ -197,6 +197,16 @@ void Expression::makeStartOfSectionType(SectionType type) {
*ptr = type;
}
static bool tryConstZero(Expression const &lhs, Expression const &rhs) {
Expression const &expr = lhs.isKnown() ? lhs : rhs;
return expr.isKnown() && expr.value() == 0;
}
static bool tryConstNonzero(Expression const &lhs, Expression const &rhs) {
Expression const &expr = lhs.isKnown() ? lhs : rhs;
return expr.isKnown() && expr.value() != 0;
}
/*
* Attempts to compute a constant binary AND from non-constant operands
* This is possible if one operand is a symbol belonging to an `ALIGN[N]` section, and the other is
@@ -422,6 +432,10 @@ void Expression::makeBinaryOp(RPNCommand op, Expression &&src1, Expression const
}
} else if (op == RPN_SUB && src1.isDiffConstant(src2.symbolOf())) {
data = src1.symbolOf()->getValue() - src2.symbolOf()->getValue();
} else if ((op == RPN_LOGAND || op == RPN_AND) && tryConstZero(src1, src2)) {
data = 0;
} else if (op == RPN_LOGOR && tryConstNonzero(src1, src2)) {
data = 1;
} else if (int32_t constVal; op == RPN_AND && (constVal = tryConstMask(src1, src2)) != -1) {
data = constVal;
} else {