[gcc r15-1616] late-combine: Honor targetm.cannot_copy_insn_p

[Richard Sandiford]

https://gcc.gnu.org/g:b87e19afa349691fdc91173bcf7a9afc7b3b0cb1

commit r15-1616-gb87e19afa349691fdc91173bcf7a9afc7b3b0cb1
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Tue Jun 25 18:02:35 2024 +0100

    late-combine: Honor targetm.cannot_copy_insn_p
    
    late-combine was failing to take targetm.cannot_copy_insn_p into
    account, which led to multiple definitions of PIC symbols on
    arm*-*-* targets.
    
    gcc/
            * late-combine.cc (insn_combination::substitute_nondebug_use):
            Reject second and subsequent uses if targetm.cannot_copy_insn_p
            disallows copying.

Diff:
---
 gcc/late-combine.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/late-combine.cc b/gcc/late-combine.cc
index fc75d1c56d7..b7c0bc07a8b 100644
--- a/gcc/late-combine.cc
+++ b/gcc/late-combine.cc
@@ -179,6 +179,18 @@ insn_combination::substitute_nondebug_use (use_info *use)
   if (dump_file && (dump_flags & TDF_DETAILS))
     dump_insn_slim (dump_file, use->insn ()->rtl ());
 
+  // Reject second and subsequent uses if the target does not allow
+  // the defining instruction to be copied.
+  if (targetm.cannot_copy_insn_p
+      && m_nondebug_changes.length () >= 2
+      && targetm.cannot_copy_insn_p (m_def_insn->rtl ()))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	fprintf (dump_file, "-- The target does not allow multiple"
+		 " copies of insn %d\n", m_def_insn->uid ());
+      return false;
+    }
+
   // Check that we can change the instruction pattern.  Leave recognition
   // of the result till later.
   insn_propagation prop (use_rtl, m_dest, m_src);