[PATCH] [GCC] AutoFDO: Walk predecessor edges for PHI arguments

PHI arguments are indexed by incoming edges.  function_instance::match
walked successor edges and could fail gimple_phi_arg_def_from_edge's
destination assertion during afdo_offline.

gcc/ChangeLog:

	* auto-profile.cc (function_instance::match): Walk predecessor edges
	for PHI arguments.

Regression tested on aarch64-linux-gnu with no new regressions

Signed-off-by: Kugan Vivekanandarajah <[email protected]>
---
 gcc/auto-profile.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/auto-profile.cc b/gcc/auto-profile.cc
index f4562d7f2f98..60f6b1ba480b 100644
--- a/gcc/auto-profile.cc
+++ b/gcc/auto-profile.cc
@@ -1764,7 +1764,8 @@ function_instance::match (cgraph_node *node,
 	  gcc_assert (!info);
 	  dump_stmt (phi, info, NULL, stack);
 	  counts.add (info);
-	  for (edge e : bb->succs)
+	  /* PHI arguments are indexed by incoming (predecessor) edges.  */
+	  for (edge e : bb->preds)
 	    {
 	      location_t phi_loc
 		= gimple_phi_arg_location_from_edge (phi, e);
-- 
2.34.1