[gcc r15-1696] Disable late-combine for -O0 [PR115677]

[Richard Sandiford]

https://gcc.gnu.org/g:f6081ee665fd5e4e7d37e02c69d16df0d3eead10

commit r15-1696-gf6081ee665fd5e4e7d37e02c69d16df0d3eead10
Author: Richard Sandiford <richard.sandiford@arm.com>
Date:   Thu Jun 27 14:51:37 2024 +0100

    Disable late-combine for -O0 [PR115677]
    
    late-combine relies on df, which for -O0 is only initialised late
    (pass_df_initialize_no_opt, after split1).  Other df-based passes
    cope with this by requiring optimize > 0, so this patch does the
    same for late-combine.
    
    gcc/
            PR rtl-optimization/115677
            * late-combine.cc (pass_late_combine::gate): New function.

Diff:
---
 gcc/late-combine.cc | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/late-combine.cc b/gcc/late-combine.cc
index b7c0bc07a8b..789d734692a 100644
--- a/gcc/late-combine.cc
+++ b/gcc/late-combine.cc
@@ -744,10 +744,16 @@ public:
 
   // opt_pass methods:
   opt_pass *clone () override { return new pass_late_combine (m_ctxt); }
-  bool gate (function *) override { return flag_late_combine_instructions; }
+  bool gate (function *) override;
   unsigned int execute (function *) override;
 };
 
+bool
+pass_late_combine::gate (function *)
+{
+  return optimize > 0 && flag_late_combine_instructions;
+}
+
 unsigned int
 pass_late_combine::execute (function *fn)
 {