[PATCH 4/4] fix remove_merging_phisrc()

[Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>]

The current implementation of remove_merging_phisrc() can't work correctly
when these phi-sources belong to a basic block with several children
to the same target basic block (this happens commonly with OP_SWITCH).

Fix this by directly scanning the source basic block for the presence
of any phi-source. Once identified, the processing is kept unchanged:
remove these phi-sources if a sibling phi-source will 'overwrite' them
in the target block.

Fixes: 2fdaca9e7175e62f08d259f5cb3ec7c9725bba68
Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@xxxxxxxxx>
---
 flow.c                          | 30 ++++++++++++++++++++----------
 validation/optim/multi-phisrc.c |  1 -
 2 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/flow.c b/flow.c
index c866dec80480..d46d0ee1bb7e 100644
--- a/flow.c
+++ b/flow.c
@@ -843,21 +843,26 @@ static int retarget_parents(struct basic_block *bb, struct basic_block *target)
 	return REPEAT_CFG_CLEANUP;
 }
 
-static void remove_merging_phisrc(struct basic_block *top, struct instruction *insn)
+static void remove_merging_phisrc(struct instruction *insn, struct basic_block *bot)
 {
-	struct instruction *user = insn->phi_node;
+	struct instruction *node = insn->phi_node;
 	pseudo_t phi;
 
-	FOR_EACH_PTR(user->phi_list, phi) {
+	if (!node) {
+		kill_instruction(insn);
+		return;
+	}
+
+	FOR_EACH_PTR(node->phi_list, phi) {
 		struct instruction *phisrc;
 
 		if (phi == VOID)
 			continue;
 		phisrc = phi->def;
-		if (phisrc->bb != top)
-			continue;
-		REPLACE_CURRENT_PTR(phi, VOID);
-		kill_instruction(phisrc);
+		if (phisrc->bb == bot) {
+			kill_instruction(insn);
+			return;
+		}
 	} END_FOR_EACH_PTR(phi);
 }
 
@@ -901,6 +906,14 @@ static int merge_bb(struct basic_block *top, struct basic_block *bot)
 		replace_bb_in_list(&bb->parents, bot, top, 1);
 	} END_FOR_EACH_PTR(bb);
 
+	FOR_EACH_PTR(top->insns, insn) {
+		if (!insn->bb)
+			continue;
+		if (insn->opcode != OP_PHISOURCE)
+			continue;
+		remove_merging_phisrc(insn, bot);
+	} END_FOR_EACH_PTR(insn);
+
 	kill_instruction(delete_last_instruction(&top->insns));
 	FOR_EACH_PTR(bot->insns, insn) {
 		if (!insn->bb)
@@ -910,9 +923,6 @@ static int merge_bb(struct basic_block *top, struct basic_block *bot)
 		case OP_PHI:
 			remove_merging_phi(top, insn);
 			continue;
-		case OP_PHISOURCE:
-			remove_merging_phisrc(top, insn);
-			break;
 		}
 		insn->bb = top;
 		add_instruction(&top->insns, insn);
diff --git a/validation/optim/multi-phisrc.c b/validation/optim/multi-phisrc.c
index c6f21f2db15a..ff31c0834e58 100644
--- a/validation/optim/multi-phisrc.c
+++ b/validation/optim/multi-phisrc.c
@@ -17,7 +17,6 @@ void foo(int p, int a)
 /*
  * check-name: multi-phisrc
  * check-command: test-linearize -Wno-decl $file
- * check-known-to-fail
  *
  * check-output-ignore
  * check-output-excludes: phi
-- 
2.31.1