Remove pseudos from liveness list when they are defined.

This only matters for phi-nodes, since other kinds of pseudos
should never see any use before their def anyway.

1 files changed, 14 insertions, 0 deletions

diff --git a/liveness.c b/liveness.c
index 7564ddc..214b770 100644
--- a/liveness.c
+++ b/liveness.c
@@ -311,6 +311,20 @@ static void track_pseudo_death_bb(struct basic_block *bb)
 	FOR_EACH_PTR_REVERSE(bb->insns, insn) {
 		if (!insn->bb)
 			continue;
+
+		/*
+		 * A "def" of a pseudo removes it from the liveness
+		 * list. However, we only bother doing that for
+		 * phi-nodes, since no other pseudos should ever
+		 * be even used before they are def'ed.
+		 */
+		if (insn->opcode == OP_PHISOURCE) {
+			struct instruction *phi;
+			FOR_EACH_PTR(insn->phi_users, phi) {
+				remove_pseudo(live_list, phi->target);
+			} END_FOR_EACH_PTR(phi);
+		}
+
 		dead_list = NULL;
 		track_instruction_usage(bb, insn, death_def, death_use);
 		if (dead_list) {