add more comments

[r16338]

diff --git a/ir/opt/reassoc.c b/ir/opt/reassoc.c
index 606b534..2bdac4f 100644 (file)
--- a/ir/opt/reassoc.c
+++ b/ir/opt/reassoc.c
@@ -549,7 +549,7 @@ static int reverse_rule_distributive(ir_node **node) {
                x = get_Shl_right(left);
 
                if (x == get_Shl_right(right)) {
-                       /* (a << x) +/- (b << x) */
+                       /* (a << x) +/- (b << x) ==> (a +/- b) << x */
                        a = get_Shl_left(left);
                        b = get_Shl_left(right);
                        goto transform;
@@ -558,12 +558,12 @@ static int reverse_rule_distributive(ir_node **node) {
                x = get_Mul_left(left);
 
                if (x == get_Mul_left(right)) {
-                       /* (x * a) +/- (x * b) */
+                       /* (x * a) +/- (x * b) ==> (a +/- b) * x */
                        a = get_Mul_right(left);
                        b = get_Mul_right(right);
                        goto transform;
                } else if (x == get_Mul_right(right)) {
-                       /* (x * a) +/- (b * x) */
+                       /* (x * a) +/- (b * x) ==> (a +/- b) * x */
                        a = get_Mul_right(left);
                        b = get_Mul_left(right);
                        goto transform;
@@ -572,12 +572,12 @@ static int reverse_rule_distributive(ir_node **node) {
                x = get_Mul_right(left);
 
                if (x == get_Mul_right(right)) {
-                       /* (a * x) +/- (b * x) */
+                       /* (a * x) +/- (b * x) ==> (a +/- b) * x */
                        a = get_Mul_left(left);
                        b = get_Mul_left(right);
                        goto transform;
                } else if (x == get_Mul_left(right)) {
-                       /* (a * x) +/- (x * b) */
+                       /* (a * x) +/- (x * b) ==> (a +/- b) * x */
                        a = get_Mul_left(left);
                        b = get_Mul_right(right);
                        goto transform;
@@ -630,16 +630,19 @@ static int move_consts_up(ir_node **node) {
        dbg = get_irn_dbg_info(n);
        op = get_irn_op(n);
        if (get_irn_op(l) == op) {
+               /* (a .op. b) .op. r */
                a = get_binop_left(l);
                b = get_binop_right(l);
 
                if (is_constant_expr(a)) {
+                       /* (C .op. b) .op. r ==> (r .op. b) .op. C */
                        c = a;
                        a = r;
                        blk = get_nodes_block(l);
                        dbg = dbg == get_irn_dbg_info(l) ? dbg : NULL;
                        goto transform;
                } else if (is_constant_expr(b)) {
+                       /* (a .op. C) .op. r ==> (a .op. r) .op. C */
                        c = b;
                        b = r;
                        blk = get_nodes_block(l);
@@ -647,16 +650,19 @@ static int move_consts_up(ir_node **node) {
                        goto transform;
                }
        } else if (get_irn_op(r) == op) {
+               /* l .op. (a .op. b) */
                a = get_binop_left(r);
                b = get_binop_right(r);
 
                if (is_constant_expr(a)) {
+                       /* l .op. (C .op. b) ==> (l .op. b) .op. C */
                        c = a;
                        a = l;
                        blk = get_nodes_block(r);
                        dbg = dbg == get_irn_dbg_info(r) ? dbg : NULL;
                        goto transform;
                } else if (is_constant_expr(b)) {
+                       /* l .op. (a .op. C) ==> (a .op. l) .op. C */
                        c = b;
                        b = l;
                        blk = get_nodes_block(r);
@@ -678,7 +684,7 @@ transform:
        if (ma != mb && mode_is_int(ma) && mode_is_int(mb))
                return 0;
 
-       /* check if a+b can be calculated in the same block is the old instruction */
+       /* check if (a .op. b) can be calculated in the same block is the old instruction */
        if (! block_dominates(get_nodes_block(a), blk))
                return 0;
        if (! block_dominates(get_nodes_block(b), blk))