reuse previous address constants in fold()

parseref() has code to reuse address constants, but this is not
done in other passes such as fold or isel. Introduce a new function
newcon() which takes a Con and returns a Ref for that constant, and
use this whenever creating address constants.

This is necessary to fix folding of address constants when one
operand is already folded. For example, in

	%a =l add $x, 1
	%b =l add %a, 2
	%c =w loadw %b

%a and %b were folded to $x+1 and $x+3 respectively, but then the
second add is visited again since it uses %a. This gets folded to
$x+3 as well, but as a new distinct constant. This results in %b
getting labeled as bottom instead of either constant, disabling the
replacement of %b by a constant in subsequent instructions (such
as the loadw).

1 files changed, 1 insertions, 9 deletions

diff --git a/parse.c b/parse.c
index 104ca1d..6e22e1f 100644
--- a/parse.c
+++ b/parse.c
@@ -381,7 +381,6 @@ static Ref
 parseref()
 {
 	Con c;
-	int i;
 
 	memset(&c, 0, sizeof c);
 	switch (next()) {
@@ -405,14 +404,7 @@ parseref()
 		c.type = CAddr;
 		c.label = intern(tokval.str);
 	Look:
-		for (i=0; i<curf->ncon; i++)
-			if (curf->con[i].type == c.type
-			&& curf->con[i].bits.i == c.bits.i
-			&& curf->con[i].label == c.label)
-				return CON(i);
-		vgrow(&curf->con, ++curf->ncon);
-		curf->con[i] = c;
-		return CON(i);
+		return newcon(&c, curf);
 	default:
 		return R;
 	}