gcc: merge upstream fix for PR 83496 (fixes FS#814)

This bug was causing miscompiled code related to branch delay slots

Signed-off-by: Felix Fietkau <nbd@nbd.name>

toolchain/gcc/patches/7.3.0/100-PR-rtl-optimization-83496.patch

@@ -0,0 +1,136 @@
+From: ebotcazou <ebotcazou@138bc75d-0d04-0410-961f-82ee72b054a4>
+Date: Mon, 26 Feb 2018 16:29:30 +0000
+Subject: [PATCH] 	PR rtl-optimization/83496 	* reorg.c
+ (steal_delay_list_from_target): Change REDUNDANT array from 	booleans to
+ RTXes.  Call fix_reg_dead_note on every non-null element.
+ (steal_delay_list_from_fallthrough): Call fix_reg_dead_note on a
+ redundant insn, if any. 	(relax_delay_slots): Likewise.
+ (update_reg_unused_notes): Rename REDUNDANT_INSN to OTHER_INSN.
+
+git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@257996 138bc75d-0d04-0410-961f-82ee72b054a4
+---
+ create mode 120000 gcc/testsuite/gcc.c-torture/execute/20180226-1.c
+
+--- a/gcc/reorg.c
++++ b/gcc/reorg.c
+@@ -1035,7 +1035,8 @@ check_annul_list_true_false (int annul_t
+ 
+ static void
+ steal_delay_list_from_target (rtx_insn *insn, rtx condition, rtx_sequence *seq,
+-			      vec<rtx_insn *> *delay_list, resources *sets,
++			      vec<rtx_insn *> *delay_list,
++			      struct resources *sets,
+ 			      struct resources *needed,
+ 			      struct resources *other_needed,
+ 			      int slots_to_fill, int *pslots_filled,
+@@ -1048,7 +1049,7 @@ steal_delay_list_from_target (rtx_insn *
+   int used_annul = 0;
+   int i;
+   struct resources cc_set;
+-  bool *redundant;
++  rtx_insn **redundant;
+ 
+   /* We can't do anything if there are more delay slots in SEQ than we
+      can handle, or if we don't know that it will be a taken branch.
+@@ -1087,7 +1088,7 @@ steal_delay_list_from_target (rtx_insn *
+   if (! targetm.can_follow_jump (insn, seq->insn (0)))
+     return;
+ 
+-  redundant = XALLOCAVEC (bool, XVECLEN (seq, 0));
++  redundant = XALLOCAVEC (rtx_insn *, XVECLEN (seq, 0));
+   for (i = 1; i < seq->len (); i++)
+     {
+       rtx_insn *trial = seq->insn (i);
+@@ -1151,7 +1152,10 @@ steal_delay_list_from_target (rtx_insn *
+      we therefore decided not to copy.  */
+   for (i = 1; i < seq->len (); i++)
+     if (redundant[i])
+-      update_block (seq->insn (i), insn);
++      {
++	fix_reg_dead_note (redundant[i], insn);
++	update_block (seq->insn (i), insn);
++      }
+ 
+   /* Show the place to which we will be branching.  */
+   *pnew_thread = first_active_target_insn (JUMP_LABEL (seq->insn (0)));
+@@ -1198,6 +1202,7 @@ steal_delay_list_from_fallthrough (rtx_i
+   for (i = 1; i < seq->len (); i++)
+     {
+       rtx_insn *trial = seq->insn (i);
++      rtx_insn *prior_insn;
+ 
+       /* If TRIAL sets CC0, stealing it will move it too far from the use
+ 	 of CC0.  */
+@@ -1209,8 +1214,9 @@ steal_delay_list_from_fallthrough (rtx_i
+ 	break;
+ 
+       /* If this insn was already done, we don't need it.  */
+-      if (redundant_insn (trial, insn, *delay_list))
++      if ((prior_insn = redundant_insn (trial, insn, *delay_list)))
+ 	{
++	  fix_reg_dead_note (prior_insn, insn);
+ 	  update_block (trial, insn);
+ 	  delete_from_delay_slot (trial);
+ 	  continue;
+@@ -1790,15 +1796,14 @@ fix_reg_dead_note (rtx_insn *start_insn,
+       }
+ }
+ 
+-/* Delete any REG_UNUSED notes that exist on INSN but not on REDUNDANT_INSN.
++/* Delete any REG_UNUSED notes that exist on INSN but not on OTHER_INSN.
+ 
+    This handles the case of udivmodXi4 instructions which optimize their
+-   output depending on whether any REG_UNUSED notes are present.
+-   we must make sure that INSN calculates as many results as REDUNDANT_INSN
+-   does.  */
++   output depending on whether any REG_UNUSED notes are present.  We must
++   make sure that INSN calculates as many results as OTHER_INSN does.  */
+ 
+ static void
+-update_reg_unused_notes (rtx_insn *insn, rtx redundant_insn)
++update_reg_unused_notes (rtx_insn *insn, rtx other_insn)
+ {
+   rtx link, next;
+ 
+@@ -1810,8 +1815,7 @@ update_reg_unused_notes (rtx_insn *insn,
+ 	  || !REG_P (XEXP (link, 0)))
+ 	continue;
+ 
+-      if (! find_regno_note (redundant_insn, REG_UNUSED,
+-			     REGNO (XEXP (link, 0))))
++      if (!find_regno_note (other_insn, REG_UNUSED, REGNO (XEXP (link, 0))))
+ 	remove_note (insn, link);
+     }
+ }
+@@ -2324,9 +2328,8 @@ follow_jumps (rtx label, rtx_insn *jump,
+    taken and THREAD_IF_TRUE is set.  This is used for the branch at the
+    end of a loop back up to the top.
+ 
+-   OWN_THREAD and OWN_OPPOSITE_THREAD are true if we are the only user of the
+-   thread.  I.e., it is the fallthrough code of our jump or the target of the
+-   jump when we are the only jump going there.
++   OWN_THREAD is true if we are the only user of the thread, i.e. it is
++   the target of the jump when we are the only jump going there.
+ 
+    If OWN_THREAD is false, it must be the "true" thread of a jump.  In that
+    case, we can only take insns from the head of the thread for our delay
+@@ -3117,7 +3120,7 @@ relax_delay_slots (rtx_insn *first)
+   /* Look at every JUMP_INSN and see if we can improve it.  */
+   for (insn = first; insn; insn = next)
+     {
+-      rtx_insn *other;
++      rtx_insn *other, *prior_insn;
+       bool crossing;
+ 
+       next = next_active_insn (insn);
+@@ -3223,8 +3226,9 @@ relax_delay_slots (rtx_insn *first)
+       /* See if the first insn in the delay slot is redundant with some
+ 	 previous insn.  Remove it from the delay slot if so; then set up
+ 	 to reprocess this insn.  */
+-      if (redundant_insn (pat->insn (1), delay_insn, vNULL))
++      if ((prior_insn = redundant_insn (pat->insn (1), delay_insn, vNULL)))
+ 	{
++	  fix_reg_dead_note (prior_insn, insn);
+ 	  update_block (pat->insn (1), insn);
+ 	  delete_from_delay_slot (pat->insn (1));
+ 	  next = prev_active_insn (next);