[gcc r12-7604] [PR103074] LRA: Check new conflicts when splitting hard reg live range.

[Vladimir Makarov <vmakarov@gcc.gnu.org>]

https://gcc.gnu.org/g:d8e5fff6b74b82c2ac3254be9a1f0fb6b30dbdbf

commit r12-7604-gd8e5fff6b74b82c2ac3254be9a1f0fb6b30dbdbf
Author: Vladimir N. Makarov <vmakarov@redhat.com>
Date:   Thu Mar 10 16:16:00 2022 -0500

    [PR103074] LRA: Check new conflicts when splitting hard reg live range.
    
    Splitting hard register live range can create (artificial)
    conflict of the hard register with another pseudo because of simplified
    conflict calculation in LRA.  We should check such conflict on the next
    assignment sub-pass and spill and reassign the pseudo if necessary.
    The patch implements this.
    
    gcc/ChangeLog:
    
            PR target/103074
            * lra-constraints.cc (split_reg): Set up
            check_and_force_assignment_correctness_p when splitting hard
            register live range.
    
    gcc/testsuite/ChangeLog:
    
            PR target/103074
            * gcc.target/i386/pr103074.c: New.

Diff:
---
 gcc/lra-constraints.cc                   |  9 +++++++--
 gcc/testsuite/gcc.target/i386/pr103074.c | 16 ++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 080b44ad87a..d92ab76908c 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -5994,12 +5994,17 @@ split_reg (bool before_p, int original_regno, rtx_insn *insn,
 			 before_p ? NULL : save,
 			 call_save_p
 			 ?  "Add save<-reg" : "Add split<-reg");
-  if (nregs > 1)
+  if (nregs > 1 || original_regno < FIRST_PSEUDO_REGISTER)
     /* If we are trying to split multi-register.  We should check
        conflicts on the next assignment sub-pass.  IRA can allocate on
        sub-register levels, LRA do this on pseudos level right now and
        this discrepancy may create allocation conflicts after
-       splitting.  */
+       splitting.
+
+       If we are trying to split hard register we should also check conflicts
+       as such splitting can create artificial conflict of the hard register
+       with another pseudo because of simplified conflict calculation in
+       LRA.  */
     check_and_force_assignment_correctness_p = true;
   if (lra_dump_file != NULL)
     fprintf (lra_dump_file,
diff --git a/gcc/testsuite/gcc.target/i386/pr103074.c b/gcc/testsuite/gcc.target/i386/pr103074.c
new file mode 100644
index 00000000000..276ad82a1de
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr103074.c
@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-march=bonnell -Os -fPIC -fschedule-insns -w" } */
+
+void
+serialize_collection (char *ptr, int a, int need_owner)
+{
+  if (need_owner)
+    __builtin_sprintf(ptr, "%d:%d", 0, a);
+  else
+    {
+      static char buff[32];
+
+      __builtin_sprintf(buff, "%d:%d", a >> 32, a);
+      __builtin_sprintf(ptr, "%d:%d:\"%s\"", 0, 0, buff);
+    }
+}