diff --git a/gcc/sched-deps.cc b/gcc/sched-deps.cc
index e0d3c97d935..f9290c82fd2 100644
--- a/gcc/sched-deps.cc
+++ b/gcc/sched-deps.cc
@@ -38,6 +38,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "sched-int.h"
 #include "cselib.h"
 #include "function-abi.h"
+#include "print-rtl.h"
 
 #ifdef INSN_SCHEDULING
 
@@ -432,10 +433,24 @@ dep_spec_p (dep_t dep)
   return false;
 }
 
+/* These regsets describe how a single instruction affects registers.
+   Their "life-time" is restricted to a single call of sched_analyze_insn().
+   They are populated by sched_analyze_1() and sched_analyze_2(), and
+   then sched_analyze_insn() transfers data from these into deps->reg_last[i].
+   Near the end sched_analyze_insn() clears these regsets for the next
+   insn.  */
 static regset reg_pending_sets;
 static regset reg_pending_clobbers;
 static regset reg_pending_uses;
 static regset reg_pending_control_uses;
+
+/* Similar to reg_pending_* regsets, this variable specifies whether
+   the current insn analyzed by sched_analyze_insn() is a scheduling
+   barrier that should "split" dependencies inside a block.  Internally
+   sched-deps.cc does this by pretending that the barrier insn uses and
+   sets all registers.
+   Near the end sched_analyze_insn() transfers barrier info from this variable
+   into deps->last_reg_pending_barrier.  */
 static enum reg_pending_barrier_mode reg_pending_barrier;
 
 /* Hard registers implicitly clobbered or used (or may be implicitly
@@ -2880,7 +2895,77 @@ get_implicit_reg_pending_clobbers (HARD_REG_SET *temp, rtx_insn *insn)
   *temp &= ~ira_no_alloc_regs;
 }
 
-/* Analyze an INSN with pattern X to find all dependencies.  */
+/* Dump state of reg_pending_* data for debug purposes.
+   Dump only non-empty data to reduce log clobber.  */
+static void
+dump_reg_pending_data (FILE *file, rtx_insn *insn)
+{
+  fprintf (file, "\n");
+  fprintf (file, ";; sched_analysis after insn %d: %s\n",
+	   INSN_UID (insn), str_pattern_slim (PATTERN (insn)));
+
+  if (!REG_SET_EMPTY_P (reg_pending_sets)
+      || !REG_SET_EMPTY_P (reg_pending_clobbers)
+      || !REG_SET_EMPTY_P (reg_pending_uses)
+      || !REG_SET_EMPTY_P (reg_pending_control_uses))
+    {
+      fprintf (file, ";; insn reg");
+      if (!REG_SET_EMPTY_P (reg_pending_sets))
+	{
+	  fprintf (file, " sets(");
+	  dump_regset (reg_pending_sets, file);
+	  fprintf (file, ")");
+	}
+      if (!REG_SET_EMPTY_P (reg_pending_clobbers))
+	{
+	  fprintf (file, " clobbers(");
+	  dump_regset (reg_pending_clobbers, file);
+	  fprintf (file, ")");
+	}
+      if (!REG_SET_EMPTY_P (reg_pending_uses))
+	{
+	  fprintf (file, " uses(");
+	  dump_regset (reg_pending_uses, file);
+	  fprintf (file, ")");
+	}
+      if (!REG_SET_EMPTY_P (reg_pending_control_uses))
+	{
+	  fprintf (file, " control(");
+	  dump_regset (reg_pending_control_uses, file);
+	  fprintf (file, ")");
+	}
+      fprintf (file, "\n");
+    }
+
+  if (reg_pending_barrier)
+    fprintf (file, ";; insn reg barrier: %d\n", reg_pending_barrier);
+
+  if (!hard_reg_set_empty_p (implicit_reg_pending_clobbers)
+      || !hard_reg_set_empty_p (implicit_reg_pending_uses))
+    {
+      fprintf (file, ";; insn reg");
+      if (!hard_reg_set_empty_p (implicit_reg_pending_clobbers))
+	{
+	  print_hard_reg_set (file, implicit_reg_pending_clobbers,
+			      " implicit clobbers(", false);
+	  fprintf (file, ")");
+	}
+      if (!hard_reg_set_empty_p (implicit_reg_pending_uses))
+	{
+	  print_hard_reg_set (file, implicit_reg_pending_uses,
+			      " implicit uses(", false);
+	  fprintf (file, ")");
+	}
+      fprintf (file, "\n");
+    }
+}
+
+/* Analyze an INSN with pattern X to find all dependencies.
+   This analysis uses two main data structures:
+   1. reg_pending_* data contains effects of INSN on the register file,
+      which is then incorporated into ...
+   2. deps_desc object, which contains commulative information about all
+      instructions processed from deps_desc object's initialization.  */
 static void
 sched_analyze_insn (class deps_desc *deps, rtx x, rtx_insn *insn)
 {
@@ -3328,6 +3413,9 @@ sched_analyze_insn (class deps_desc *deps, rtx x, rtx_insn *insn)
       deps->last_reg_pending_barrier = reg_pending_barrier;
     }
 
+  if (sched_verbose >= 8)
+    dump_reg_pending_data (sched_dump, insn);
+
   CLEAR_REG_SET (reg_pending_uses);
   CLEAR_REG_SET (reg_pending_clobbers);
   CLEAR_REG_SET (reg_pending_sets);
