ia32: Add peephole optimization 'lea c(, %i, 2), %d' -> 'lea c(%i, %i), %d'.

With base the displacement may be a single byte.

NEWS.md

@@ -16,6 +16,7 @@ libFirm 1.22.1 (2016-01-07)
 * Add peephole optimization 'mov $0, %r' -> 'xorl %r, %r' (amd64)
 * Add peephole optimization 'lea c(%r), %r' -> 'add $c, %r' (amd64)
 * Add peephole optimization 'lea (%r1, %r2), %r1' -> 'add %r2, %r1' and the commutated case (amd64)
+* Add peephole optimization 'lea c(, %i, 2), %d' -> 'lea c(%i, %i), %d' (ia32)
 * Bugfixes
 
 libFirm 1.22.0 (2015-12-31)

ir/be/ia32/ia32_optimize.c

@@ -948,9 +948,15 @@ exchange:
 				arch_set_irn_register(res, oreg);
 				SET_IA32_ORIG_NODE(res, node);
 				replace(node, res);
+				return;
 			}
 		}
 	}
+	if (!breg && scale == 1) {
+		/* lea c(, %i, 2), %d -> lea c(%i, %i), %d */
+		set_irn_n(node, n_ia32_Lea_base, idx);
+		set_ia32_am_scale(node, 0);
+	}
 }
 
 /**