[gcc r12-6149] loop-invariant: Don't move cold bb instructions to preheader in RTL

[gcc r12-6149] loop-invariant: Don't move cold bb instructions to preheader in RTL

[Xiong Hu Luo]

https://gcc.gnu.org/g:dc1969dab392661cdac1170bbb8c9f83f388580d

commit r12-6149-gdc1969dab392661cdac1170bbb8c9f83f388580d
Author: Xionghu Luo <luoxhu@linux.ibm.com>
Date:   Wed Dec 29 20:02:12 2021 -0600

    loop-invariant: Don't move cold bb instructions to preheader in RTL
    
    gcc/ChangeLog:
    
    2021-12-30  Xionghu Luo  <luoxhu@linux.ibm.com>
    
            * loop-invariant.c (find_invariants_bb): Check profile count
            before motion.
            (find_invariants_body): Add argument.
    
    gcc/testsuite/ChangeLog:
    
    2021-12-30  Xionghu Luo  <luoxhu@linux.ibm.com>
    
            * gcc.dg/loop-invariant-2.c: New.

Diff:
---
 gcc/loop-invariant.c                    | 17 ++++++++++++++---
 gcc/testsuite/gcc.dg/loop-invariant-2.c | 20 ++++++++++++++++++++
 2 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/gcc/loop-invariant.c b/gcc/loop-invariant.c
index be951554337..d69a0c16e33 100644
--- a/gcc/loop-invariant.c
+++ b/gcc/loop-invariant.c
@@ -1183,9 +1183,21 @@ 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 (class loop *loop, basic_block bb, bool always_reached,
+		    bool always_executed)
 {
   rtx_insn *insn;
+  basic_block preheader = loop_preheader_edge (loop)->src;
+
+  /* Don't move insn of cold BB out of loop to preheader to reduce calculations
+     and register live range in hot loop with cold BB.  */
+  if (!always_executed && preheader->count > bb->count)
+    {
+      if (dump_file)
+	fprintf (dump_file, "Don't move invariant from bb: %d out of loop %d\n",
+		 bb->index, loop->num);
+      return;
+    }
 
   FOR_BB_INSNS (bb, insn)
     {
@@ -1214,8 +1226,7 @@ find_invariants_body (class loop *loop, basic_block *body,
   unsigned i;
 
   for (i = 0; i < loop->num_nodes; i++)
-    find_invariants_bb (body[i],
-			bitmap_bit_p (always_reached, i),
+    find_invariants_bb (loop, body[i], bitmap_bit_p (always_reached, i),
 			bitmap_bit_p (always_executed, i));
 }
 
diff --git a/gcc/testsuite/gcc.dg/loop-invariant-2.c b/gcc/testsuite/gcc.dg/loop-invariant-2.c
new file mode 100644
index 00000000000..df3d8458569
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/loop-invariant-2.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-rtl-loop2_invariant" } */
+
+volatile int x;
+void
+bar (int, char *, char *);
+void
+foo (int *a, int n, int k)
+{
+  int i;
+
+  for (i = 0; i < n; i++)
+    {
+      if (__builtin_expect (x, 0))
+	bar (k / 5, "one", "two");
+      a[i] = k;
+    }
+}
+
+/* { dg-final { scan-rtl-dump "Don't move invariant from bb: .*out of loop" "loop2_invariant" } } */