Fix PR rtl-optimization/94119

Message ID 3073123.yoXOXRUpF6@polaris
State New
Headers show
Series
  • Fix PR rtl-optimization/94119
Related show

Commit Message

Eric Botcazou March 13, 2020, 9:10 a.m.
This is a regression present on all active branches: the dbr pass goes awry on 
a branchy testcase compiled at -O2 for the MIPS, with specific set of options 
(-fno-reorder-blocks -mlong-calls) which leave the CFG in a convoluted state.

The underlynig issue is that relax_delay_slots can streamline the CFG in these 
cases, in particular remove BARRIERs, but removing BARRIERs changes the way 
the instructions are associated with (basic) blocks by the liveness analysis 
code in resource.c (find_basic_block) and thus can cause entries in the cache 
maintained by resource.c to become outdated, thus producing wrong answers.

The fix is to invalidate the cache entries affected by the removal of BARRIERs 
in relax_delay_slots, i.e. for the instructions down to the next BARRIER.

Bootstrapped/regtested on SPAR/Solaris & SPARC64/Linux, applied on all active 
branches (without a testcase because it's MIPS specific and I don't understand 
hows gcc.target/mips works, see mips.exp for the gory details).


2019-03-13  Eric Botcazou  <ebotcazou@adacore.com>

	PR rtl-optimization/94119
	* resource.h (clear_hashed_info_until_next_barrier): Declare.
	* resource.c (clear_hashed_info_until_next_barrier): New function.
	* reorg.c (add_to_delay_list): Fix formatting.
	(relax_delay_slots): Call clear_hashed_info_until_next_barrier on
	the next instruction after removing a BARRIER.

-- 
Eric Botcazou

Patch

diff --git a/gcc/reorg.c b/gcc/reorg.c
index dfd7494bf79..84beb9395aa 100644
--- a/gcc/reorg.c
+++ b/gcc/reorg.c
@@ -575,8 +575,9 @@  add_to_delay_list (rtx_insn *insn, vec<rtx_insn *> *delay_list)
 {
   /* If INSN has its block number recorded, clear it since we may
      be moving the insn to a new block.  */
-      clear_hashed_info_for_insn (insn);
-      delay_list->safe_push (insn);
+  clear_hashed_info_for_insn (insn);
+
+  delay_list->safe_push (insn);
 }
 
 /* Delete INSN from the delay slot of the insn that it is in, which may
@@ -3211,7 +3212,14 @@  relax_delay_slots (rtx_insn *first)
 
 	      if (invert_jump (jump_insn, label, 1))
 		{
-		  delete_related_insns (next);
+		  rtx_insn *from = delete_related_insns (next);
+
+		  /* We have just removed a BARRIER, which means that the block
+		     number of the next insns has effectively been changed (see
+		     find_basic_block in resource.c), so clear it.  */
+		  if (from)
+		    clear_hashed_info_until_next_barrier (from);
+
 		  next = jump_insn;
 		}
 
@@ -3484,18 +3492,22 @@  relax_delay_slots (rtx_insn *first)
 
 	      if (invert_jump (delay_jump_insn, label, 1))
 		{
-		  int i;
-
 		  /* Must update the INSN_FROM_TARGET_P bits now that
 		     the branch is reversed, so that mark_target_live_regs
 		     will handle the delay slot insn correctly.  */
-		  for (i = 1; i < XVECLEN (PATTERN (insn), 0); i++)
+		  for (int i = 1; i < XVECLEN (PATTERN (insn), 0); i++)
 		    {
 		      rtx slot = XVECEXP (PATTERN (insn), 0, i);
 		      INSN_FROM_TARGET_P (slot) = ! INSN_FROM_TARGET_P (slot);
 		    }
 
-		  delete_related_insns (next);
+		  /* We have just removed a BARRIER, which means that the block
+		     number of the next insns has effectively been changed (see
+		     find_basic_block in resource.c), so clear it.  */
+		  rtx_insn *from = delete_related_insns (next);
+		  if (from)
+		    clear_hashed_info_until_next_barrier (from);
+
 		  next = insn;
 		}
 
diff --git a/gcc/resource.c b/gcc/resource.c
index d26217c056b..5ce53e61057 100644
--- a/gcc/resource.c
+++ b/gcc/resource.c
@@ -1283,6 +1283,25 @@  clear_hashed_info_for_insn (rtx_insn *insn)
     }
 }
 
+/* Clear any hashed information that we have stored for instructions
+   between INSN and the next BARRIER that follow a JUMP or a LABEL.  */
+
+void
+clear_hashed_info_until_next_barrier (rtx_insn *insn)
+{
+  while (insn && !BARRIER_P (insn))
+    {
+      if (JUMP_P (insn) || LABEL_P (insn))
+	{
+	  rtx_insn *next = next_active_insn (insn);
+	  if (next)
+	    clear_hashed_info_for_insn (next);
+	}
+
+      insn = next_nonnote_insn (insn);
+    }
+}
+
 /* Increment the tick count for the basic block that contains INSN.  */
 
 void
diff --git a/gcc/resource.h b/gcc/resource.h
index e3edb242703..c4f8aa20141 100644
--- a/gcc/resource.h
+++ b/gcc/resource.h
@@ -46,6 +46,7 @@  extern void mark_set_resources (rtx, struct resources *, int,
 				enum mark_resource_type);
 extern void mark_referenced_resources (rtx, struct resources *, bool);
 extern void clear_hashed_info_for_insn (rtx_insn *);
+extern void clear_hashed_info_until_next_barrier (rtx_insn *);
 extern void incr_ticks_for_insn (rtx_insn *);
 extern void mark_end_of_function_resources (rtx, bool);
 extern void init_resource_info (rtx_insn *);