[pushed][PR117105][LRA]: Use unique value reload pseudo for early clobber operand

[Vladimir Makarov]

The following patch solves

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117105
The patch was successfully tested and bootstrapped on x86-64, ppc64le, 
aarch64.
commit 4b09e2c67ef593db171b0755b46378964421782b
Author: Vladimir N. Makarov <vmaka...@redhat.com>
Date:   Mon Nov 25 16:09:00 2024 -0500

    [PR117105][LRA]: Use unique value reload pseudo for early clobber operand
    
    LRA did not generate insn satisfying insn constraints on the PR
    test.  The reason for this is that LRA assigned the same hard reg for
    two conflicting reload pseudos.  The two insn reload pseudos are
    originated from the same pseudo and LRA tried to optimize as it
    assigned the same value for the reload pseudos.  It is an LRA
    optimization to minimize reload insns.  The two reload pseudos
    conflict as one of them is an early clobber insn operands.  The patch
    solves this problem by assigning unique value if the operand is early
    clobber one.
    
    gcc/ChangeLog:
    
            PR target/117105
            * lra-constraints.cc (get_reload_reg): Create unique value reload
            pseudos for early clobbered operands.
    
    gcc/testsuite/ChangeLog:
    
            PR target/117105
            * gcc.target/i386/pr117105.c: New test.

diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc
index 61bbb930b7f..052e5f71f1e 100644
--- a/gcc/lra-constraints.cc
+++ b/gcc/lra-constraints.cc
@@ -663,7 +663,6 @@ get_reload_reg (enum op_type type, machine_mode mode, rtx original,
 {
   int i, regno;
   enum reg_class new_class;
-  bool unique_p = false;
 
   if (type == OP_OUT)
     {
@@ -702,6 +701,8 @@ get_reload_reg (enum op_type type, machine_mode mode, rtx original,
 						exclude_start_hard_regs, title);
       return true;
     }
+
+  bool unique_p = early_clobber_p;
   /* Prevent reuse value of expression with side effects,
      e.g. volatile memory.  */
   if (! side_effects_p (original))
diff --git a/gcc/testsuite/gcc.target/i386/pr117105.c b/gcc/testsuite/gcc.target/i386/pr117105.c
new file mode 100644
index 00000000000..252bb138c9c
--- /dev/null
+++ b/gcc/testsuite/gcc.target/i386/pr117105.c
@@ -0,0 +1,15 @@
+/* { dg-do compile } */
+/* { dg-options "-O3 -fno-code-hoisting -fno-tree-fre -fno-tree-dominator-opts -fno-tree-pre -fno-tree-sra" } */
+int a;
+struct b {
+  char c;
+  char d;
+};
+int main() {
+  struct b e;
+  int f;
+  while (a)
+    if (f == e.d)
+      f = e.c = e.d & 1 >> e.d;
+  return 0;
+}