Re: [PATCH 2/2] better dealing with OP_PHISOURCE insn

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Reformulated comment to better describe what it does.

(Sorry for inconvenience)

Signed-off-by: Jan Pokorny <pokorny_jan@xxxxxxxxx>
---
 liveness.c |   29 ++++++++++++++++++++---------
 1 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/liveness.c b/liveness.c
index eeff0f7..8c15645 100644
--- a/liveness.c
+++ b/liveness.c
@@ -13,21 +13,32 @@
 #include "flow.h"
 
 static void phi_defines(struct instruction * phi_node, pseudo_t target,
-	void (*defines)(struct basic_block *, struct instruction *, pseudo_t))
+	void (*defines)(struct basic_block *, struct instruction *, pseudo_t),
+	unsigned long generation)
 {
 	pseudo_t phi;
 	FOR_EACH_PTR(phi_node->phi_list, phi) {
-		struct instruction *def;
 		if (phi == VOID)
 			continue;
-		def = phi->def;
-		if (!def || !def->bb)
-			continue;
-		if (def->opcode == OP_PHI) {
-			phi_defines(def, target, defines);
+		if (!phi->def || !phi->def->bb)
 			continue;
+
+		/*
+		 * In case of "(PHISOURCE->PHI->)+ PHISOURCE->PHI" chain, move
+		 * "defines" information upstream to BBs of very initial PHISOURCEs;
+		 * recursion guarded by generation marking of PHI instructions BBs.
+		 */
+		pseudo_t src_pseudo = phi->def->phi_src;
+		if (src_pseudo->type == PSEUDO_REG
+		    && src_pseudo->def->opcode == OP_PHI) {
+			phi_node->bb->generation = generation;
+			if (src_pseudo->def->bb->generation != generation) {
+				phi_defines(src_pseudo->def, target, defines, generation);
+				continue;
+			}
 		}
-		defines(def->bb, phi->def, target);
+
+		defines(phi->def->bb, phi->def, target);
 	} END_FOR_EACH_PTR(phi);
 }
 
@@ -103,7 +114,7 @@ static void track_instruction_usage(struct basic_block *bb, struct instruction *
 	/* Other */
 	case OP_PHI:
 		/* Phi-nodes are "backwards" nodes. Their def doesn't matter */
-		phi_defines(insn, insn->target, def);
+		phi_defines(insn, insn->target, def, ++bb_generation);
 		break;
 
 	case OP_PHISOURCE:
-- 
1.7.1
--
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