[PATCH v2 3/4] [SPARC] Errata workaround for GRLIB-TN-0010

[Daniel Cederman <cederman@gaisler.com>]

This patch provides a workaround for the errata described in GRLIB-TN-0010.

If the workaround is enabled it will:

* Insert a NOP between load instruction and atomic
  instruction (swap, ldstub, casa).

* Insert a NOP at branch target if load in delay slot
  and atomic instruction at branch target.

It is applicable to UT700.

gcc/ChangeLog:

2017-11-17  Daniel Cederman  <cederman@gaisler.com>

	* config/sparc/sparc.c (atomic_insn_p): New function.
	(sparc_do_work_around_errata): Insert NOP instructions to
	prevent sequences that could trigger the TN-0010 errata for
	UT700.
	* config/sparc/sync.md (atomic_compare_and_swap_leon3_1): Make
	instruction referable in atomic_insns_p.
---
 gcc/config/sparc/sparc.c | 41 +++++++++++++++++++++++++++++++++++++++++
 gcc/config/sparc/sync.md |  2 +-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index 51045db..401dfcb 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -970,6 +970,22 @@ fpop_insn_p (rtx_insn *insn)
     }
 }
 
+/* True if INSN is an atomic instruction.  */
+
+static bool
+atomic_insn_for_leon3_p (rtx_insn *insn)
+{
+  switch (INSN_CODE (insn))
+    {
+    case CODE_FOR_swapsi:
+    case CODE_FOR_ldstub:
+    case CODE_FOR_atomic_compare_and_swap_leon3_1:
+      return true;
+    default:
+      return false;
+    }
+}
+
 /* We use a machine specific pass to enable workarounds for errata.
 
    We need to have the (essentially) final form of the insn stream in order
@@ -1024,6 +1040,31 @@ sparc_do_work_around_errata (void)
 	    emit_insn_before (gen_nop (), target);
 	}
 
+      /* Insert a NOP between load instruction and atomic
+	 instruction.  Insert a NOP at branch target if load
+	 in delay slot and atomic instruction at branch target.  */
+      if (sparc_fix_ut700
+	  && NONJUMP_INSN_P (insn)
+	  && (set = single_set (insn)) != NULL_RTX
+	  && MEM_P (SET_SRC (set))
+	  && REG_P (SET_DEST (set)))
+	{
+	  if (jump)
+	    {
+	      rtx_insn *target = next_active_insn (JUMP_LABEL_AS_INSN (jump));
+	      if (target
+		  && atomic_insn_for_leon3_p (target))
+		emit_insn_before (gen_nop (), target);
+	    }
+
+	  next = next_active_insn (insn);
+	  if (!next)
+	    break;
+
+	  if (atomic_insn_for_leon3_p (next))
+	    insert_nop = true;
+	}
+
       /* Look for either of these two sequences:
 
 	 Sequence A:
diff --git a/gcc/config/sparc/sync.md b/gcc/config/sparc/sync.md
index ead7c77..43c66e9 100644
--- a/gcc/config/sparc/sync.md
+++ b/gcc/config/sparc/sync.md
@@ -212,7 +212,7 @@
   "cas<modesuffix>\t%1, %2, %0"
   [(set_attr "type" "multi")])
 
-(define_insn "*atomic_compare_and_swap_leon3_1"
+(define_insn "atomic_compare_and_swap_leon3_1"
   [(set (match_operand:SI 0 "register_operand" "=r")
 	(match_operand:SI 1 "mem_noofs_operand" "+w"))
    (set (match_dup 1)
-- 
2.9.3