From c11cc6a24a1f3e134126dc8bfff4bbff50a268bf Mon Sep 17 00:00:00 2001
From: benniaobufeijiushiji <linda7@huawei.com>
Date: Sun, 12 Jun 2022 23:12:07 +0800
Subject: [PATCH] [LIM] Optimize for loop invariant motion Don't move cold bb
 instructions to preheader in RTL reference
 [https://gcc.gnu.org/pipermail/gcc-patches/2021-December/586372.html]

---
 gcc/common.opt       |  4 ++++
 gcc/loop-invariant.c | 12 ++++++++++--
 2 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/gcc/common.opt b/gcc/common.opt
index 7fc075d354a..a462330066a 100644
--- a/gcc/common.opt
+++ b/gcc/common.opt
@@ -2861,6 +2861,10 @@ ftree-loop-im
 Common Report Var(flag_tree_loop_im) Init(1) Optimization
 Enable loop invariant motion on trees.
 
+flim-count-check
+Common Report Var(flag_lim_count_check) Init(0) Optimization
+Check bb count for not hoisting cold code to hotter bbs.
+
 ftree-loop-linear
 Common Alias(floop-nest-optimize)
 Enable loop nest transforms.  Same as -floop-nest-optimize.
diff --git a/gcc/loop-invariant.c b/gcc/loop-invariant.c
index 37ae6549e56..613a41f5c53 100644
--- a/gcc/loop-invariant.c
+++ b/gcc/loop-invariant.c
@@ -1184,10 +1184,18 @@ find_invariants_insn (rtx_insn *insn, bool always_reached, bool always_executed)
    call.  */
 
 static void
-find_invariants_bb (basic_block bb, bool always_reached, bool always_executed)
+find_invariants_bb (struct loop *loop, basic_block bb, bool always_reached,
+		    bool always_executed)
 {
   rtx_insn *insn;
 
+  basic_block preheader = loop_preheader_edge (loop)->src;
+
+  if (flag_lim_count_check && preheader->count > bb->count)
+    {
+      return;
+    }
+
   FOR_BB_INSNS (bb, insn)
     {
       if (!NONDEBUG_INSN_P (insn))
@@ -1215,7 +1223,7 @@ find_invariants_body (class loop *loop, basic_block *body,
   unsigned i;
 
   for (i = 0; i < loop->num_nodes; i++)
-    find_invariants_bb (body[i],
+    find_invariants_bb (loop, body[i],
 			bitmap_bit_p (always_reached, i),
 			bitmap_bit_p (always_executed, i));
 }
-- 
Gitee