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Proper signedness of comparison operands 

Comparison operands are signed only of both operands are signed.
If one is unsigned, then they both are unsigned. This does not
affect the signedness of the comparison itself, which is unsigned.

Signed-off-by: Stephen Williams <steve@icarus.com>
This commit is contained in:
Stephen Williams 2007-11-24 20:32:35 -08:00
parent ea70ae00aa
commit 79232f46d8
2 changed files with 18 additions and 0 deletions
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2
PExpr.h
View File

@ -525,6 +525,8 @@ class PEBinary : public PExpr {
NetEBinary*elaborate_expr_base_(Design*, NetExpr*lp, NetExpr*rp, int use_wid) const;
NetEBinary*elaborate_eval_expr_base_(Design*, NetExpr*lp, NetExpr*rp, int use_wid) const;
static void surpress_operand_sign_if_needed_(NetExpr*lp, NetExpr*rp);
private:
NetNet* elaborate_net_add_(Design*des, NetScope*scope,
unsigned lwidth,

16
elab_expr.cc
View File

@ -111,6 +111,20 @@ NetEBinary* PEBinary::elaborate_expr(Design*des, NetScope*scope,
return tmp;
}
void PEBinary::surpress_operand_sign_if_needed_(NetExpr*lp, NetExpr*rp)
{
// If either operand is unsigned, then treat the whole
// expression as unsigned. This test needs to be done hear
// instead of in *_expr_base_ because it needs to be done
// ahead of any subexpression evaluation (because they need to
// know their signedness to evaluate) and because there are
// exceptions to this rule.
if (! lp->has_sign())
rp->cast_signed(false);
if (! rp->has_sign())
lp->cast_signed(false);
}
NetEBinary* PEBinary::elaborate_eval_expr_base_(Design*des,
NetExpr*lp,
NetExpr*rp,
@ -296,6 +310,8 @@ NetEBinary* PEBComp::elaborate_expr(Design*des, NetScope*scope,
return 0;
}
surpress_operand_sign_if_needed_(lp, rp);
return elaborate_eval_expr_base_(des, lp, rp, use_wid);
}