shift bugs

R=r
OCL=18095
CL=18095

src/cmd/gc/const.c

@@ -12,6 +12,7 @@ convlit(Node *n, Type *t)
 
 	if(n == N || t == T)
 		return;
+
 	switch(n->op) {
 	default:
 		return;
@@ -25,7 +26,6 @@ convlit(Node *n, Type *t)
 	}
 
 	et = t->etype;
-
 	wt = whatis(n);
 
 	switch(wt) {

src/cmd/gc/mparith2.c

@@ -84,7 +84,7 @@ mprsh(Mpint *a)
 		if(x & 1)
 			c = Mpbase;
 	}
-	if(a->neg && lo == 0)
+	if(a->neg && lo != 0)
 		mpaddcfix(a, -1);
 }
 
@@ -105,7 +105,7 @@ mprshw(Mpint *a)
 		a1++;
 	}
 	a1[0] = 0;
-	if(a->neg && lo == 0)
+	if(a->neg && lo != 0)
 		mpaddcfix(a, -1);
 }
 

src/cmd/gc/walk.c

@@ -170,6 +170,8 @@ walktype(Node *n, int top)
 	int et, cl, cr;
 	int32 lno;
 
+	if(n == N)
+		return;
 	lno = setlineno(n);
 
 	/*
@@ -645,8 +647,10 @@ loop:
 		evconst(n);
 		if(n->op == OLITERAL)
 			goto ret;
-		convlit(n->right, types[TUINT]);
-		convlit(n->left, types[TINT]);
+		if(n->left->type == T)
+			convlit(n->left, types[TINT]);
+		if(n->right->type == T)
+			convlit(n->right, types[TUINT]);
 		if(n->left->type == T || n->right->type == T)
 			goto ret;
 		if(issigned[n->right->type->etype])