Fix incorrect filling of delay slots in branchy code at -O2

The issue is that relax_delay_slots can streamline the CFG in some 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cache maintained by resource.c to become outdated, thus producing wrong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 downstream.

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.

	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.

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 7b573c07abc38865fcd2c798a34e6ba90b45823b..61982897e1194c3120cfd3a6f6cf247b56d3e6ec 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,12 @@
+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.
+
 2019-03-13  Eric Botcazou  <ebotcazou@adacore.com>
 
        PR middle-end/92071

diff --git a/gcc/reorg.c b/gcc/reorg.c
index dfd7494bf79d4558efba816c421b6366d5cdcaf4..84beb9395aa546169155de2d80b60d41d364c87d 100644 (file)
--- 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);
 }
 \f
 /* 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 d26217c056b9a15da70a8dde7eb9f5811a4eaa60..32faa73fd5fa72cebfc7c3d3687164ca450a6a3a 100644 (file)
--- a/gcc/resource.c
+++ b/gcc/resource.c
@@ -1282,7 +1282,26 @@ clear_hashed_info_for_insn (rtx_insn *insn)
        tinfo->block = -1;
     }
 }
-\f
+
+/* 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 e3edb2427035f2cc3fbcdc71a5c14173c09459b8..c4f8aa2014104cad82f26bd31c03858690c47aa1 100644 (file)
--- 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 *);