From: Michael Beck <beck@ipd.info.uni-karlsruhe.de>
Date: Wed, 21 May 2008 15:09:50 +0000 (+0000)
Subject: assure_different_constraints():
X-Git-Url: http://nsz.repo.hu/git/?a=commitdiff_plain;h=f18baed9c341f6cd95ec6d6a61236df29b35ce8b;p=libfirm

assure_different_constraints():
we can safely IGNORE the should_be_different constraint, iff
we have only one, one should be same and both inputs are identical, for instance in
sbb(x,x)

[r19702]
---

diff --git a/ir/be/belower.c b/ir/be/belower.c
index ea016785d..bdef20634 100644
--- a/ir/be/belower.c
+++ b/ir/be/belower.c
@@ -633,6 +633,22 @@ static void assure_different_constraints(ir_node *irn, constraint_env_t *env) {
 		const unsigned other = req->other_different;
 		int i;
 
+		if (arch_register_req_is(req, should_be_same)) {
+			const unsigned same = req->other_same;
+
+			if (is_po2(other) && is_po2(same)) {
+				int idx_other = ntz(other);
+				int idx_same  = ntz(same);
+
+				/*
+				 * We can safely ignore a should_be_same x should_be_different y
+				 * IFF both nodes are equal!
+				 */
+				if (get_irn_n(irn, idx_other) == get_irn_n(irn, idx_same)) {
+					return;
+				}
+			}
+		}
 		for (i = 0; 1U << i <= other; ++i) {
 			if (other & (1U << i)) {
 				ir_node *different_from = get_irn_n(belower_skip_proj(irn), i);