1. Go group spotted that a slightly-obscured pointer move was done by AMOVL not AMOVQ.
2. Inspecting the code further, I noticed that other pointer types were set to TLONG not TIND,
   causing similar truncation of pointers to 32 bits.

Reference: /n/sources/patch/applied/6c-sugen-types
Date: Thu Feb 28 10:28:48 CET 2013
Signed-off-by: charles.forsyth@gmail.com

--- /sys/src/cmd/6c/cgen.c	Thu Feb 28 10:26:39 2013
+++ /sys/src/cmd/6c/cgen.c	Thu Feb 28 10:26:33 2013
@@ -1596,7 +1596,7 @@
 		regsalloc(&nod2, nn);
 		nn->type = t;
 
-		gins(AMOVL, &nod1, &nod2);
+		gins(AMOVQ, &nod1, &nod2);
 		regfree(&nod1);
 
 		nod2.type = typ(TIND, t);
@@ -1697,7 +1697,7 @@
 	c = 0;
 	if(n->complex > nn->complex) {
 		t = n->type;
-		n->type = types[TLONG];
+		n->type = types[TIND];
 		nodreg(&nod1, n, D_SI);
 		if(reg[D_SI]) {
 			gins(APUSHQ, &nod1, Z);
@@ -1708,7 +1708,7 @@
 		n->type = t;
 
 		t = nn->type;
-		nn->type = types[TLONG];
+		nn->type = types[TIND];
 		nodreg(&nod2, nn, D_DI);
 		if(reg[D_DI]) {
 warn(Z, "DI botch");
@@ -1720,7 +1720,7 @@
 		nn->type = t;
 	} else {
 		t = nn->type;
-		nn->type = types[TLONG];
+		nn->type = types[TIND];
 		nodreg(&nod2, nn, D_DI);
 		if(reg[D_DI]) {
 warn(Z, "DI botch");
@@ -1732,7 +1732,7 @@
 		nn->type = t;
 
 		t = n->type;
-		n->type = types[TLONG];
+		n->type = types[TIND];
 		nodreg(&nod1, n, D_SI);
 		if(reg[D_SI]) {
 			gins(APUSHQ, &nod1, Z);