[PATCH 1/4] [SPARC] Errata workaround for GRLIB-TN-0012

[Daniel Cederman <cederman at gaisler dot com>]

This patch provides a workaround for the errata described in GRLIB-TN-0012.

If the workaround is enabled it will:

* Prevent any floating-point operation from being placed in the
  delay slot of an annulled integer branch.

* Place a NOP at the branch target of an integer branch if it is
  a floating-point operation or a floating-point branch.

It is applicable to GR712RC.

gcc/ChangeLog:

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

	* config/sparc/sparc.c (fpop_insn_p): New function.
	(sparc_do_work_around_errata): Insert NOP instructions to
	prevent sequences that could trigger the TN-0012 errata for
	GR712RC.
	(pass_work_around_errata::gate): Also test sparc_fix_gr712rc.
	* config/sparc/sparc.md (fix_gr712rc): New attribute.
	(in_branch_annul_delay): Prevent floating-point instructions
	in delay slot of annulled integer branch.
---
 gcc/config/sparc/sparc.c  | 50 +++++++++++++++++++++++++++++++++++++++++++++--
 gcc/config/sparc/sparc.md | 17 ++++++++++++++++
 2 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/gcc/config/sparc/sparc.c b/gcc/config/sparc/sparc.c
index a9945e2..8f6eb48 100644
--- a/gcc/config/sparc/sparc.c
+++ b/gcc/config/sparc/sparc.c
@@ -945,6 +945,31 @@ mem_ref (rtx x)
   return NULL_RTX;
 }
 
+/* True if floating-point instruction.  */
+
+static int
+fpop_insn_p (rtx_insn *insn)
+{
+  if ( GET_CODE (PATTERN (insn)) != SET)
+    return false;
+
+  switch (get_attr_type (insn))
+    {
+    case TYPE_FPMOVE:
+    case TYPE_FPCMOVE:
+    case TYPE_FP:
+    case TYPE_FPCMP:
+    case TYPE_FPMUL:
+    case TYPE_FPDIVS:
+    case TYPE_FPSQRTS:
+    case TYPE_FPDIVD:
+    case TYPE_FPSQRTD:
+      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
@@ -970,11 +995,31 @@ sparc_do_work_around_errata (void)
     {
       bool insert_nop = false;
       rtx set;
+      rtx_insn *jump = 0;
 
       /* Look into the instruction in a delay slot.  */
       if (NONJUMP_INSN_P (insn))
 	if (rtx_sequence *seq = dyn_cast <rtx_sequence *> (PATTERN (insn)))
-	  insn = seq->insn (1);
+	  {
+	    jump = seq->insn (0);
+	    insn = seq->insn (1);
+	  }
+
+      /* Place a NOP at the branch target of an integer branch if it is
+	 a floating-point operation or a floating-point branch.  */
+      if (sparc_fix_gr712rc
+	  && (JUMP_P (insn) || jump)
+	  && get_attr_branch_type (jump ? jump : insn) == BRANCH_TYPE_ICC)
+	{
+	  rtx_insn *target;
+
+	  target = next_active_insn (JUMP_LABEL_AS_INSN (jump ? jump : insn));
+	  if (target
+	      && (fpop_insn_p (target)
+		  || ((JUMP_P (target)
+		       && get_attr_branch_type (target) == BRANCH_TYPE_FCC))))
+	    emit_insn_before (gen_nop (), target);
+	}
 
       /* Look for either of these two sequences:
 
@@ -1303,7 +1348,8 @@ public:
   /* opt_pass methods: */
   virtual bool gate (function *)
     {
-      return sparc_fix_at697f || sparc_fix_ut699 || sparc_fix_b2bst;
+      return sparc_fix_at697f || sparc_fix_ut699 || sparc_fix_b2bst
+	|| sparc_fix_gr712rc;
     }
 
   virtual unsigned int execute (function *)
diff --git a/gcc/config/sparc/sparc.md b/gcc/config/sparc/sparc.md
index d9cbd4f..ef789e2 100644
--- a/gcc/config/sparc/sparc.md
+++ b/gcc/config/sparc/sparc.md
@@ -430,6 +430,10 @@
    (symbol_ref "(sparc_fix_b2bst != 0
 		 ? FIX_B2BST_TRUE : FIX_B2BST_FALSE)"))
 
+(define_attr "fix_gr712rc" "false,true"
+   (symbol_ref "(sparc_fix_gr712rc != 0
+		 ? FIX_GR712RC_TRUE : FIX_GR712RC_FALSE)"))
+
 ;; Length (in # of insns).
 ;; Beware that setting a length greater or equal to 3 for conditional branches
 ;; has a side-effect (see output_cbranch and output_v9branch).
@@ -590,6 +594,15 @@
 	   (const_string "true")
 	] (const_string "false")))
 
+(define_attr "in_branch_annul_delay" "false,true"
+  (cond[(and (eq_attr "fix_gr712rc" "true")
+	     (eq_attr "type" "fp,fpcmp,fpmove,fpcmove,fpmul,
+			      fpdivs,fpsqrts,fpdivd,fpsqrtd"))
+	   (const_string "false")
+	(eq_attr "in_branch_delay" "true")
+	   (const_string "true")
+	] (const_string "false")))
+
 (define_delay (eq_attr "type" "call")
   [(eq_attr "in_call_delay" "true") (nil) (nil)])
 
@@ -602,6 +615,10 @@
 (define_delay (eq_attr "type" "branch")
   [(eq_attr "in_branch_delay" "true") (nil) (eq_attr "in_branch_delay" "true")])
 
+(define_delay (and (eq_attr "type" "branch") (eq_attr "branch_type" "icc"))
+  [(eq_attr "in_branch_delay" "true") (nil)
+  (eq_attr "in_branch_annul_delay" "true")])
+
 (define_delay (eq_attr "type" "uncond_branch")
   [(eq_attr "in_branch_delay" "true") (nil) (nil)])
 
-- 
2.9.3