[PATCH] RISC-V: Avoid redundant flow in forward fusion

[juzhe.zhong@rivai.ai]

From: Ju-Zhe Zhong <juzhe.zhong@rivai.ai>

gcc/ChangeLog:

        * config/riscv/riscv-vsetvl.cc (pass_vsetvl::forward_demand_fusion): Add pre-check for redundant flow.

---
 gcc/config/riscv/riscv-vsetvl.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/gcc/config/riscv/riscv-vsetvl.cc b/gcc/config/riscv/riscv-vsetvl.cc
index 7800c2ee509..18c6f437db6 100644
--- a/gcc/config/riscv/riscv-vsetvl.cc
+++ b/gcc/config/riscv/riscv-vsetvl.cc
@@ -2140,6 +2140,9 @@ pass_vsetvl::forward_demand_fusion (void)
       if (!prop.valid_or_dirty_p ())
 	continue;
 
+      if (cfg_bb == ENTRY_BLOCK_PTR_FOR_FN (cfun))
+	continue;
+
       edge e;
       edge_iterator ei;
       /* Forward propagate to each successor.  */
@@ -2153,6 +2156,11 @@ pass_vsetvl::forward_demand_fusion (void)
 	  /* It's quite obvious, we don't need to propagate itself.  */
 	  if (e->dest->index == cfg_bb->index)
 	    continue;
+	  /* We don't propagate through critical edges.  */
+	  if (e->flags & EDGE_COMPLEX)
+	    continue;
+	  if (e->dest->index == EXIT_BLOCK_PTR_FOR_FN (cfun)->index)
+	    continue;
 
 	  /* If there is nothing to propagate, just skip it.  */
 	  if (!local_dem.valid_or_dirty_p ())
-- 
2.36.1