diff --git a/src/amd/compiler/aco_lower_to_cssa.cpp b/src/amd/compiler/aco_lower_to_cssa.cpp
index c4eb542f03c..65fcdac40b9 100644
--- a/src/amd/compiler/aco_lower_to_cssa.cpp
+++ b/src/amd/compiler/aco_lower_to_cssa.cpp
@@ -56,9 +56,12 @@ struct merge_node {
    uint32_t index = -1u;      /* index into the vector of merge sets */
    uint32_t defined_at = -1u; /* defining block */
 
-   /* we also remember two dominating defs with the same value: */
+   /* We also remember two closest equal intersecting ancestors. Because they intersect with this
+    * merge node, they must dominate it (intersection isn't possible otherwise) and have the same
+    * value (or else they would not be allowed to be in the same merge set).
+    */
    Temp equal_anc_in = Temp();  /* within the same merge set */
-   Temp equal_anc_out = Temp(); /* from a different set */
+   Temp equal_anc_out = Temp(); /* from the other set we're currently trying to merge with */
 };
 
 struct cssa_ctx {
@@ -243,7 +246,7 @@ intersects(cssa_ctx& ctx, Temp var, Temp parent)
 
 /* check interference between var and parent:
  * i.e. they have different values and intersect.
- * If parent and var share the same value, also updates the equal ancestor. */
+ * If parent and var intersect and share the same value, also updates the equal ancestor. */
 inline bool
 interference(cssa_ctx& ctx, Temp var, Temp parent)
 {
@@ -252,12 +255,13 @@ interference(cssa_ctx& ctx, Temp var, Temp parent)
    node_var.equal_anc_out = Temp();
 
    if (node_var.index == ctx.merge_node_table[parent.id()].index) {
-      /* check/update in other set */
+      /* Check/update in other set. equal_anc_out is only present if it intersects with 'parent',
+       * but that's fine since it has to for it to intersect with 'var'. */
       parent = ctx.merge_node_table[parent.id()].equal_anc_out;
    }
 
    Temp tmp = parent;
-   /* check if var intersects with parent or any equal-valued ancestor */
+   /* Check if 'var' intersects with 'parent' or any ancestors which might intersect too. */
    while (tmp != Temp() && !intersects(ctx, var, tmp)) {
       merge_node& node_tmp = ctx.merge_node_table[tmp.id()];
       tmp = node_tmp.equal_anc_in;
@@ -267,7 +271,7 @@ interference(cssa_ctx& ctx, Temp var, Temp parent)
    if (tmp == Temp())
       return false;
 
-   /* var and parent, same value, but in different sets */
+   /* var and parent, same value and intersect, but in different sets */
    if (node_var.value == ctx.merge_node_table[parent.id()].value) {
       node_var.equal_anc_out = tmp;
       return false;
@@ -320,7 +324,7 @@ try_merge_merge_set(cssa_ctx& ctx, Temp dst, merge_set& set_b)
    for (Temp t : union_set) {
       merge_node& node = ctx.merge_node_table[t.id()];
       /* update the equal ancestors:
-       * i.e. the 'closest' dominating def with the same value */
+       * i.e. the 'closest' dominating def which intersects */
       Temp in = node.equal_anc_in;
       Temp out = node.equal_anc_out;
       if (in == Temp() || (out != Temp() && defined_after(ctx, out, in)))