opt: Simplify computed goto with known destination to unconditional branch.

NEWS.md

@@ -36,6 +36,7 @@ libFirm 1.22.1 (2016-01-07)
 * sparc: Support the asm constaint `K`
 * sparc: Support computed goto
 * arm: Support computed goto
+* opt: Simplify computed goto with known destination to unconditional branch
 * Bugfixes
 
 libFirm 1.22.0 (2015-12-31)

ir/opt/iropt.c

@@ -5740,11 +5740,28 @@ static ir_node *transform_node_Block(ir_node *block)
 	ir_node *bad   = NULL;
 	for (int i = 0; i < arity; ++i) {
 		ir_node *const pred = get_Block_cfgpred(block, i);
-		if (is_Bad(pred) || !is_block_unreachable(get_nodes_block(pred)))
+		if (is_Bad(pred)) {
 			continue;
-		if (bad == NULL)
-			bad = new_r_Bad(irg, mode_X);
-		set_irn_n(block, i, bad);
+		} else if (is_block_unreachable(get_nodes_block(pred))) {
+			goto bad;
+		} else if (is_IJmp(pred)) {
+			ir_node *const target = get_IJmp_target(pred);
+			if (is_Address(target)) {
+				ir_entity *const entity = get_Address_entity(target);
+				if (entity == get_Block_entity(block)) {
+					/* BB[x](..., IJmp(Adress[x]), ...)  ==>  BB[x](..., Jmp, ...) */
+					dbg_info *const dbgi = get_irn_dbg_info(pred);
+					ir_node*  const jmp  = new_rd_Jmp(dbgi, get_nodes_block(pred));
+					set_irn_n(block, i, jmp);
+				} else {
+					/* BB[x](..., IJmp(Adress[y]), ...), x != y  ==>  BB[x](..., Bad, ...) */
+bad:
+					if (!bad)
+						bad = new_r_Bad(irg, mode_X);
+					set_irn_n(block, i, bad);
+				}
+			}
+		}
 	}
 
 	return block;