rtl.def (PREFETCH): New rtx code.

* rtl.def (PREFETCH): New rtx code.
	* doc/rtl.texi (PREFETCH): Add documentation.
	* function.c (instantiate_virtual_regs_1): Handle PREFETCH rtx.
	* rtlanal.c (reg_referenced_p): Ditto.
	* sched-vis.c (print_exp):  Ditto.
	* ssa-dce.c (find_inherently_necessary):  Ditto.

From-SVN: r47580

gcc/doc/rtl.texi

@@ -2326,6 +2326,20 @@ are set up by branch shortening and hold a label with a minimum and a
 maximum address, respectively.  @var{flags} indicates the relative
 position of @var{base}, @var{min} and @var{max} to the containing insn
 and of @var{min} and @var{max} to @var{base}.  See rtl.def for details.
+
+@findex prefetch
+@item (prefetch:@var{m} @var{addr} @var{rw} @var{locality})
+Represents prefetch of memory at address @var{addr}.
+Operand @var{rw} is 1 if the prefetch is for data to be written, 0 otherwise;
+targets that do not support write prefetches should treat this as a normal
+prefetch.
+Operand @var{locality} specifies the amount of temporal locality; 0 if there
+is none or 1, 2, or 3 for increasing levels of temporal locality;
+targets that do not support locality hints should ignore this.
+
+This insn is used to minimize cache-miss latency by moving data into a
+cache before it is accessed.  It should use only non-faulting data prefetch
+instructions.
 @end table
 
 @node Incdec

gcc/function.c

@@ -3979,6 +3979,7 @@ instantiate_virtual_regs_1 (loc, object, extra_insns)
 	}
 
       /* Fall through to generic unary operation case.  */
+    case PREFETCH:
     case SUBREG:
     case STRICT_LOW_PART:
     case NEG:          case NOT:

gcc/rtl.def

@@ -514,6 +514,17 @@ DEF_RTL_EXPR(ADDR_VEC, "addr_vec", "E", 'x')
      
 DEF_RTL_EXPR(ADDR_DIFF_VEC, "addr_diff_vec", "eEee0", 'x')
 
+/* Memory prefetch, with attributes supported on some targets.
+   Operand 1 is the address of the memory to fetch.
+   Operand 2 is 1 for a write access, 0 otherwise.
+   Operand 3 is the level of temporal locality; 0 means there is no
+   temporal locality and 1, 2, and 3 are for increasing levels of temporal
+   locality.
+
+   The attributes specified by operands 2 and 3 are ignored for targets
+   whose prefetch instructions do not support them.  */
+DEF_RTL_EXPR(PREFETCH, "prefetch", "eee", 'x')
+
 /* ----------------------------------------------------------------------
    At the top level of an instruction (perhaps under PARALLEL).
    ---------------------------------------------------------------------- */

gcc/rtlanal.c

@@ -569,6 +569,9 @@ reg_referenced_p (x, body)
     case TRAP_IF:
       return reg_overlap_mentioned_p (x, TRAP_CONDITION (body));
 
+    case PREFETCH:
+      return reg_overlap_mentioned_p (x, XEXP (body, 0));
+
     case UNSPEC:
     case UNSPEC_VOLATILE:
       for (i = XVECLEN (body, 0) - 1; i >= 0; i--)
@@ -1456,6 +1459,10 @@ note_uses (pbody, fun, data)
       (*fun) (&TRAP_CONDITION (body), data);
       return;
 
+    case PREFETCH:
+      (*fun) (&XEXP (body, 0), data);
+      return;
+
     case UNSPEC:
     case UNSPEC_VOLATILE:
       for (i = XVECLEN (body, 0) - 1; i >= 0; i--)

gcc/sched-vis.c

@@ -474,6 +474,12 @@ print_exp (buf, x, verbose)
       fun = "trap_if";
       op[0] = TRAP_CONDITION (x);
       break;
+    case PREFETCH:
+      fun = "prefetch";
+      op[0] = XEXP (x, 0);
+      op[1] = XEXP (x, 1);
+      op[2] = XEXP (x, 2);
+      break;
     case UNSPEC:
     case UNSPEC_VOLATILE:
       {

gcc/ssa-dce.c

@@ -373,6 +373,7 @@ find_inherently_necessary (x)
       {  
       case CALL_INSN:
       case BARRIER:
+      case PREFETCH:
 	return !0;
       case CODE_LABEL:
       case NOTE: