[pushed] Add a debug counter for late-combine

[pushed] Add a debug counter for late-combine

[Richard Sandiford]

This should help to diagnose problems like PR115631.

Bootstrapped & regression-tested on aarch64-linux-gnu, pushed as obvious.

Richard


gcc/
	* dbgcnt.def (late_combine): New debug counter.
	* late-combine.cc (insn_combination::run): Use it.
---
 gcc/dbgcnt.def      | 1 +
 gcc/late-combine.cc | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/gcc/dbgcnt.def b/gcc/dbgcnt.def
index ed9f062eac2..e0b9b1b2a76 100644
--- a/gcc/dbgcnt.def
+++ b/gcc/dbgcnt.def
@@ -186,6 +186,7 @@ DEBUG_COUNTER (ipa_sra_params)
 DEBUG_COUNTER (ipa_sra_retvalues)
 DEBUG_COUNTER (ira_move)
 DEBUG_COUNTER (ivopts_loop)
+DEBUG_COUNTER (late_combine)
 DEBUG_COUNTER (lim)
 DEBUG_COUNTER (local_alloc_for_sched)
 DEBUG_COUNTER (loop_unswitch)
diff --git a/gcc/late-combine.cc b/gcc/late-combine.cc
index 22a1d81d38e..fc75d1c56d7 100644
--- a/gcc/late-combine.cc
+++ b/gcc/late-combine.cc
@@ -41,6 +41,7 @@
 #include "tree-pass.h"
 #include "cfgcleanup.h"
 #include "target.h"
+#include "dbgcnt.h"
 
 using namespace rtl_ssa;
 
@@ -428,6 +429,11 @@ insn_combination::run ()
       || !crtl->ssa->verify_insn_changes (m_nondebug_changes))
     return false;
 
+  // We've now decided that the optimization is valid and profitable.
+  // Allow it to be suppressed for bisection purposes.
+  if (!dbg_cnt (::late_combine))
+    return false;
+
   substitute_optional_uses (m_def);
 
   confirm_change_group ();
-- 
2.25.1