[committed] [PR97684] IRA: Recalculate pseudo classes if we added new pseduos since last calculation before updating equiv regs

[Vladimir Makarov via Gcc-patches]

The patch solves the following problem:

  https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97684

The patch was successfully bootstrapped and tested on x86-64.


commit 238ea13cca75ad499f227b60a95c40174c6caf78
Author: Vladimir N. Makarov <vmaka...@redhat.com>
Date:   Wed Jan 27 14:53:28 2021 -0500

    [PR97684] IRA: Recalculate pseudo classes if we added new pseduos since last calculation before updating equiv regs
    
    update_equiv_regs can use reg classes of pseudos and they are set up in
    register pressure sensitive scheduling and loop invariant motion and in
    live range shrinking.  This info can become obsolete if we add new pseudos
    since the last set up.  Recalculate it again if the new pseudos were
    added.
    
    gcc/ChangeLog:
    
            PR rtl-optimization/97684
            * ira.c (ira): Call ira_set_pseudo_classes before
            update_equiv_regs when it is necessary.
    
    gcc/testsuite/ChangeLog:
    
            PR rtl-optimization/97684
            * gcc.target/i386/pr97684.c: New.

diff --git a/gcc/ira.c b/gcc/ira.c
index f0bdbc8cf56..c32ecf814fd 100644
--- a/gcc/ira.c
+++ b/gcc/ira.c
@@ -5566,6 +5566,15 @@ ira (FILE *f)
   if (warn_clobbered)
     generate_setjmp_warnings ();
 
+  /* update_equiv_regs can use reg classes of pseudos and they are set up in
+     register pressure sensitive scheduling and loop invariant motion and in
+     live range shrinking.  This info can become obsolete if we add new pseudos
+     since the last set up.  Recalculate it again if the new pseudos were
+     added.  */
+  if (resize_reg_info () && (flag_sched_pressure || flag_live_range_shrinkage
+			     || flag_ira_loop_pressure))
+    ira_set_pseudo_classes (true, ira_dump_file);
+
   init_alias_analysis ();
   loop_optimizer_init (AVOID_CFG_MODIFICATIONS);
   reg_equiv = XCNEWVEC (struct equivalence, max_reg_num ());
@@ -5610,9 +5619,6 @@ ira (FILE *f)
       regstat_recompute_for_max_regno ();
     }
 
-  if (resize_reg_info () && flag_ira_loop_pressure)
-    ira_set_pseudo_classes (true, ira_dump_file);
-
   setup_reg_equiv ();
   grow_reg_equivs ();
   setup_reg_equiv_init ();
diff --git a/gcc/testsuite/gcc.target/i386/pr97684.c b/gcc/testsuite/gcc.target/i386/pr97684.c
new file mode 100644
index 00000000000..983bf535ad8
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr97684.c
@@ -0,0 +1,24 @@
+/* PR rtl-optimization/97684 */
+/* { dg-do compile } */
+/* { dg-options "-O1 -flive-range-shrinkage -fschedule-insns -fselective-scheduling -funroll-all-loops -fno-web" } */
+
+void
+c5 (double);
+
+void
+g4 (int *n4)
+{
+  double lp = 0.0;
+  int fn;
+
+  for (fn = 0; fn < 18; ++fn)
+    {
+      int as;
+
+      as = __builtin_abs (n4[fn]);
+      if (as > lp)
+        lp = as;
+    }
+
+  c5 (lp);
+}