Patchwork [(1/7)] New optab framework for widening multiplies

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Submitter Andrew Stubbs
Date June 23, 2011, 2:37 p.m.
Message ID <4E034F98.5000809@codesourcery.com>
Download mbox | patch
Permalink /patch/101632/
State New
Headers show

Comments

Andrew Stubbs - June 23, 2011, 2:37 p.m.
This patch should have no effect on the compiler output. It merely 
replaces one way to represent widening operations with another, and 
refactors the other parts of the compiler to match. The rest of the 
patch set uses this new framework to implement the optimization 
improvements.

I considered and discarded many approaches to this patch before arriving 
at this solution, and I feel sure that there'll be somebody out there 
who will think I chose the wrong one, so let me first explain how I got 
here ....

The aim is to be able to encode and query optabs that have any given 
input mode, and any given output mode. This is similar to the 
convert_optab, but not compatible with that optab since it is handled 
completely differently in the code.

(Just to be clear, the existing widening multiply support only covers 
instructions that widen by *one* mode, so it's only ever been necessary 
to know the output mode, up to now.)

Option 1 was to add a second dimension to the handlers table in optab_d, 
but I discarded this option because it would increase the memory usage 
by the square of the number of modes, which is a bit much.

Option 2 was to add a whole new optab, similar to optab_d, but with a 
second dimension like convert_optab_d, however this turned out to cause 
way too many pointer type mismatches in the code, and would have been 
very difficult to fix up.

Option 3 was to add new optab entries for widening by two modes, by 
three modes, and so on. True, I would only need to add one extra set for 
what I need, but there would be so many places in the code that compare 
against smul_widen_optab, for example, that would need to be taught 
about these, that it seemed like a bad idea.

Option 4 was to have a separate table that contained the widening 
operations, and refer to that whenever a widening entry in the main 
optab is referenced, but I found that there was no easy way to do the 
mapping without putting some sort of switch table in 
widening_optab_handler, and that negates the other advantages.

So, what I've done in the end is add a new pointer entry "widening" into 
optab_d, and dynamically build the widening operations table for each 
optab that needs it. I've then added new accessor functions that take 
both input and output modes, and altered the code to use them where 
appropriate.

The down-side of this approach is that the optab entries for widening 
operations now have two "handlers" tables, one of which is redundant. 
That said, those cases are in the minority, and it is the smaller table 
which is unused.

If people find that very distasteful, it might be possible to remove the 
*_widen_optab entries and unify smul_optab with smul_widen_optab, and so 
on, and save space that way. I've not done so yet, but I expect I could 
if people feel strongly about it.

As a side-effect, it's now possible for any optab to be "widening", 
should some target happen to have a widening add, shift, or whatever.

Is this patch OK?

Andrew

Patch

2011-06-23  Andrew Stubbs  <ams@codesourcery.com>

	gcc/
	* expr.c (expand_expr_real_2): Use widening_optab_handler.
	* genopinit.c (optabs): Use set_widening_optab_handler for $N.
	(gen_insn): $N now means $a must be wider than $b, not consecutive.
	* optabs.c (expand_widen_pattern_expr): Use widening_optab_handler.
	(expand_binop_directly): Likewise.
	(expand_binop): Likewise.
	* optabs.h (widening_optab_handlers): New struct.
	(optab_d): New member, 'widening'.
	(widening_optab_handler): New function.
	(set_widening_optab_handler): New function.
	* tree-ssa-math-opts.c (convert_mult_to_widen): Use
	widening_optab_handler.
	(convert_plusminus_to_widen): Likewise.

--- a/gcc/expr.c
+++ b/gcc/expr.c
@@ -7634,7 +7634,8 @@  expand_expr_real_2 (sepops ops, rtx target, enum machine_mode tmode,
 	  this_optab = usmul_widen_optab;
 	  if (mode == GET_MODE_2XWIDER_MODE (innermode))
 	    {
-	      if (optab_handler (this_optab, mode) != CODE_FOR_nothing)
+	      if (widening_optab_handler (this_optab, mode, innermode)
+		    != CODE_FOR_nothing)
 		{
 		  if (TYPE_UNSIGNED (TREE_TYPE (treeop0)))
 		    expand_operands (treeop0, treeop1, NULL_RTX, &op0, &op1,
@@ -7661,7 +7662,8 @@  expand_expr_real_2 (sepops ops, rtx target, enum machine_mode tmode,
 	  if (mode == GET_MODE_2XWIDER_MODE (innermode)
 	      && TREE_CODE (treeop0) != INTEGER_CST)
 	    {
-	      if (optab_handler (this_optab, mode) != CODE_FOR_nothing)
+	      if (widening_optab_handler (this_optab, mode, innermode)
+		    != CODE_FOR_nothing)
 		{
 		  expand_operands (treeop0, treeop1, NULL_RTX, &op0, &op1,
 				   EXPAND_NORMAL);
@@ -7669,7 +7671,8 @@  expand_expr_real_2 (sepops ops, rtx target, enum machine_mode tmode,
 					       unsignedp, this_optab);
 		  return REDUCE_BIT_FIELD (temp);
 		}
-	      if (optab_handler (other_optab, mode) != CODE_FOR_nothing
+	      if (widening_optab_handler (other_optab, mode, innermode)
+		    != CODE_FOR_nothing
 		  && innermode == word_mode)
 		{
 		  rtx htem, hipart;
--- a/gcc/genopinit.c
+++ b/gcc/genopinit.c
@@ -46,10 +46,12 @@  along with GCC; see the file COPYING3.  If not see
    used.  $A and $B are replaced with the full name of the mode; $a and $b
    are replaced with the short form of the name, as above.
 
-   If $N is present in the pattern, it means the two modes must be consecutive
-   widths in the same mode class (e.g, QImode and HImode).  $I means that
-   only full integer modes should be considered for the next mode, and $F
-   means that only float modes should be considered.
+   If $N is present in the pattern, it means the two modes must be in
+   the same mode class, and $b must be greater than $a (e.g, QImode
+   and HImode).
+
+   $I means that only full integer modes should be considered for the
+   next mode, and $F means that only float modes should be considered.
    $P means that both full and partial integer modes should be considered.
    $Q means that only fixed-point modes should be considered.
 
@@ -99,17 +101,17 @@  static const char * const optabs[] =
   "set_optab_handler (smulv_optab, $A, CODE_FOR_$(mulv$I$a3$))",
   "set_optab_handler (umul_highpart_optab, $A, CODE_FOR_$(umul$a3_highpart$))",
   "set_optab_handler (smul_highpart_optab, $A, CODE_FOR_$(smul$a3_highpart$))",
-  "set_optab_handler (smul_widen_optab, $B, CODE_FOR_$(mul$a$b3$)$N)",
-  "set_optab_handler (umul_widen_optab, $B, CODE_FOR_$(umul$a$b3$)$N)",
-  "set_optab_handler (usmul_widen_optab, $B, CODE_FOR_$(usmul$a$b3$)$N)",
-  "set_optab_handler (smadd_widen_optab, $B, CODE_FOR_$(madd$a$b4$)$N)",
-  "set_optab_handler (umadd_widen_optab, $B, CODE_FOR_$(umadd$a$b4$)$N)",
-  "set_optab_handler (ssmadd_widen_optab, $B, CODE_FOR_$(ssmadd$a$b4$)$N)",
-  "set_optab_handler (usmadd_widen_optab, $B, CODE_FOR_$(usmadd$a$b4$)$N)",
-  "set_optab_handler (smsub_widen_optab, $B, CODE_FOR_$(msub$a$b4$)$N)",
-  "set_optab_handler (umsub_widen_optab, $B, CODE_FOR_$(umsub$a$b4$)$N)",
-  "set_optab_handler (ssmsub_widen_optab, $B, CODE_FOR_$(ssmsub$a$b4$)$N)",
-  "set_optab_handler (usmsub_widen_optab, $B, CODE_FOR_$(usmsub$a$b4$)$N)",
+  "set_widening_optab_handler (smul_widen_optab, $B, $A, CODE_FOR_$(mul$a$b3$)$N)",
+  "set_widening_optab_handler (umul_widen_optab, $B, $A, CODE_FOR_$(umul$a$b3$)$N)",
+  "set_widening_optab_handler (usmul_widen_optab, $B, $A, CODE_FOR_$(usmul$a$b3$)$N)",
+  "set_widening_optab_handler (smadd_widen_optab, $B, $A, CODE_FOR_$(madd$a$b4$)$N)",
+  "set_widening_optab_handler (umadd_widen_optab, $B, $A, CODE_FOR_$(umadd$a$b4$)$N)",
+  "set_widening_optab_handler (ssmadd_widen_optab, $B, $A, CODE_FOR_$(ssmadd$a$b4$)$N)",
+  "set_widening_optab_handler (usmadd_widen_optab, $B, $A, CODE_FOR_$(usmadd$a$b4$)$N)",
+  "set_widening_optab_handler (smsub_widen_optab, $B, $A, CODE_FOR_$(msub$a$b4$)$N)",
+  "set_widening_optab_handler (umsub_widen_optab, $B, $A, CODE_FOR_$(umsub$a$b4$)$N)",
+  "set_widening_optab_handler (ssmsub_widen_optab, $B, $A, CODE_FOR_$(ssmsub$a$b4$)$N)",
+  "set_widening_optab_handler (usmsub_widen_optab, $B, $A, CODE_FOR_$(usmsub$a$b4$)$N)",
   "set_optab_handler (sdiv_optab, $A, CODE_FOR_$(div$a3$))",
   "set_optab_handler (ssdiv_optab, $A, CODE_FOR_$(ssdiv$Q$a3$))",
   "set_optab_handler (sdivv_optab, $A, CODE_FOR_$(div$V$I$a3$))",
@@ -305,7 +307,7 @@  gen_insn (rtx insn)
     {
       int force_float = 0, force_int = 0, force_partial_int = 0;
       int force_fixed = 0;
-      int force_consec = 0;
+      int force_wider = 0;
       int matches = 1;
 
       for (pp = optabs[pindex]; pp[0] != '$' || pp[1] != '('; pp++)
@@ -323,7 +325,7 @@  gen_insn (rtx insn)
 	    switch (*++pp)
 	      {
 	      case 'N':
-		force_consec = 1;
+		force_wider = 1;
 		break;
 	      case 'I':
 		force_int = 1;
@@ -392,7 +394,10 @@  gen_insn (rtx insn)
 			    || mode_class[i] == MODE_VECTOR_FRACT
 			    || mode_class[i] == MODE_VECTOR_UFRACT
 			    || mode_class[i] == MODE_VECTOR_ACCUM
-			    || mode_class[i] == MODE_VECTOR_UACCUM))
+			    || mode_class[i] == MODE_VECTOR_UACCUM)
+			&& (! force_wider
+			    || *pp == 'a'
+			    || m1 < i))
 		      break;
 		  }
 
@@ -412,8 +417,7 @@  gen_insn (rtx insn)
 	}
 
       if (matches && pp[0] == '$' && pp[1] == ')'
-	  && *np == 0
-	  && (! force_consec || (int) GET_MODE_WIDER_MODE(m1) == m2))
+	  && *np == 0)
 	break;
     }
 
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -515,8 +515,8 @@  expand_widen_pattern_expr (sepops ops, rtx op0, rtx op1, rtx wide_op,
     optab_for_tree_code (ops->code, TREE_TYPE (oprnd0), optab_default);
   if (ops->code == WIDEN_MULT_PLUS_EXPR
       || ops->code == WIDEN_MULT_MINUS_EXPR)
-    icode = optab_handler (widen_pattern_optab,
-			   TYPE_MODE (TREE_TYPE (ops->op2)));
+    icode = widening_optab_handler (widen_pattern_optab,
+				    TYPE_MODE (TREE_TYPE (ops->op2)), tmode0);
   else
     icode = optab_handler (widen_pattern_optab, tmode0);
   gcc_assert (icode != CODE_FOR_nothing);
@@ -1242,7 +1242,8 @@  expand_binop_directly (enum machine_mode mode, optab binoptab,
 		       rtx target, int unsignedp, enum optab_methods methods,
 		       rtx last)
 {
-  enum insn_code icode = optab_handler (binoptab, mode);
+  enum machine_mode from_mode = GET_MODE (op0);
+  enum insn_code icode = widening_optab_handler (binoptab, mode, from_mode);
   enum machine_mode xmode0 = insn_data[(int) icode].operand[1].mode;
   enum machine_mode xmode1 = insn_data[(int) icode].operand[2].mode;
   enum machine_mode mode0, mode1, tmp_mode;
@@ -1389,7 +1390,8 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
   /* If we can do it with a three-operand insn, do so.  */
 
   if (methods != OPTAB_MUST_WIDEN
-      && optab_handler (binoptab, mode) != CODE_FOR_nothing)
+      && widening_optab_handler (binoptab, mode, GET_MODE (op0))
+	    != CODE_FOR_nothing)
     {
       temp = expand_binop_directly (mode, binoptab, op0, op1, target,
 				    unsignedp, methods, last);
@@ -1429,8 +1431,9 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
 
   if (binoptab == smul_optab
       && GET_MODE_WIDER_MODE (mode) != VOIDmode
-      && (optab_handler ((unsignedp ? umul_widen_optab : smul_widen_optab),
-			 GET_MODE_WIDER_MODE (mode))
+      && (widening_optab_handler ((unsignedp ? umul_widen_optab
+					     : smul_widen_optab),
+				  GET_MODE_WIDER_MODE (mode), mode)
 	  != CODE_FOR_nothing))
     {
       temp = expand_binop (GET_MODE_WIDER_MODE (mode),
@@ -1458,12 +1461,14 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
 	 wider_mode != VOIDmode;
 	 wider_mode = GET_MODE_WIDER_MODE (wider_mode))
       {
-	if (optab_handler (binoptab, wider_mode) != CODE_FOR_nothing
+	if (widening_optab_handler (binoptab, wider_mode, mode)
+		!= CODE_FOR_nothing
 	    || (binoptab == smul_optab
 		&& GET_MODE_WIDER_MODE (wider_mode) != VOIDmode
-		&& (optab_handler ((unsignedp ? umul_widen_optab
-				    : smul_widen_optab),
-				   GET_MODE_WIDER_MODE (wider_mode))
+		&& (widening_optab_handler ((unsignedp ? umul_widen_optab
+						       : smul_widen_optab),
+					    GET_MODE_WIDER_MODE (wider_mode),
+					    mode)
 		    != CODE_FOR_nothing)))
 	  {
 	    rtx xop0 = op0, xop1 = op1;
@@ -1896,8 +1901,8 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
       && optab_handler (add_optab, word_mode) != CODE_FOR_nothing)
     {
       rtx product = NULL_RTX;
-
-      if (optab_handler (umul_widen_optab, mode) != CODE_FOR_nothing)
+      if (widening_optab_handler (umul_widen_optab, mode, word_mode)
+	    != CODE_FOR_nothing)
 	{
 	  product = expand_doubleword_mult (mode, op0, op1, target,
 					    true, methods);
@@ -1906,7 +1911,8 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
 	}
 
       if (product == NULL_RTX
-	  && optab_handler (smul_widen_optab, mode) != CODE_FOR_nothing)
+	  && widening_optab_handler (smul_widen_optab, mode, word_mode)
+		!= CODE_FOR_nothing)
 	{
 	  product = expand_doubleword_mult (mode, op0, op1, target,
 					    false, methods);
@@ -1997,7 +2003,8 @@  expand_binop (enum machine_mode mode, optab binoptab, rtx op0, rtx op1,
 	   wider_mode != VOIDmode;
 	   wider_mode = GET_MODE_WIDER_MODE (wider_mode))
 	{
-	  if (optab_handler (binoptab, wider_mode) != CODE_FOR_nothing
+	  if (widening_optab_handler (binoptab, wider_mode, mode)
+		  != CODE_FOR_nothing
 	      || (methods == OPTAB_LIB
 		  && optab_libfunc (binoptab, wider_mode)))
 	    {
--- a/gcc/optabs.h
+++ b/gcc/optabs.h
@@ -42,6 +42,11 @@  struct optab_handlers
   int insn_code;
 };
 
+struct widening_optab_handlers
+{
+  struct optab_handlers handlers[NUM_MACHINE_MODES][NUM_MACHINE_MODES];
+};
+
 struct optab_d
 {
   enum rtx_code code;
@@ -50,6 +55,7 @@  struct optab_d
   void (*libcall_gen)(struct optab_d *, const char *name, char suffix,
 		      enum machine_mode);
   struct optab_handlers handlers[NUM_MACHINE_MODES];
+  struct widening_optab_handlers *widening;
 };
 typedef struct optab_d * optab;
 
@@ -876,6 +882,23 @@  optab_handler (optab op, enum machine_mode mode)
 			   + (int) CODE_FOR_nothing);
 }
 
+/* Like optab_handler, but for widening_operations that have a TO_MODE and
+  a FROM_MODE.  */
+
+static inline enum insn_code
+widening_optab_handler (optab op, enum machine_mode to_mode,
+			enum machine_mode from_mode)
+{
+  if (to_mode == from_mode)
+    return optab_handler (op, to_mode);
+
+  if (op->widening)
+    return (enum insn_code) (op->widening->handlers[(int) to_mode][(int) from_mode].insn_code
+			     + (int) CODE_FOR_nothing);
+
+  return CODE_FOR_nothing;
+}
+
 /* Record that insn CODE should be used to implement mode MODE of OP.  */
 
 static inline void
@@ -884,6 +907,26 @@  set_optab_handler (optab op, enum machine_mode mode, enum insn_code code)
   op->handlers[(int) mode].insn_code = (int) code - (int) CODE_FOR_nothing;
 }
 
+/* Like set_optab_handler, but for widening operations that have a TO_MODE
+   and a FROM_MODE.  */
+
+static inline void
+set_widening_optab_handler (optab op, enum machine_mode to_mode,
+			    enum machine_mode from_mode, enum insn_code code)
+{
+  if (to_mode == from_mode)
+    set_optab_handler (op, to_mode, code);
+  else
+    {
+      if (op->widening == NULL)
+	op->widening = (struct widening_optab_handlers *)
+	      xcalloc (1, sizeof (struct widening_optab_handlers));
+
+      op->widening->handlers[(int) to_mode][(int) from_mode].insn_code
+	  = (int) code - (int) CODE_FOR_nothing;
+    }
+}
+
 /* Return the insn used to perform conversion OP from mode FROM_MODE
    to mode TO_MODE; return CODE_FOR_nothing if the target does not have
    such an insn.  */
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -2047,6 +2047,8 @@  convert_mult_to_widen (gimple stmt)
 {
   tree lhs, rhs1, rhs2, type, type1, type2;
   enum insn_code handler;
+  enum machine_mode to_mode, from_mode;
+  optab op;
 
   lhs = gimple_assign_lhs (stmt);
   type = TREE_TYPE (lhs);
@@ -2056,12 +2058,17 @@  convert_mult_to_widen (gimple stmt)
   if (!is_widening_mult_p (stmt, &type1, &rhs1, &type2, &rhs2))
     return false;
 
+  to_mode = TYPE_MODE (type);
+  from_mode = TYPE_MODE (type1);
+
   if (TYPE_UNSIGNED (type1) && TYPE_UNSIGNED (type2))
-    handler = optab_handler (umul_widen_optab, TYPE_MODE (type));
+    op = umul_widen_optab;
   else if (!TYPE_UNSIGNED (type1) && !TYPE_UNSIGNED (type2))
-    handler = optab_handler (smul_widen_optab, TYPE_MODE (type));
+    op = smul_widen_optab;
   else
-    handler = optab_handler (usmul_widen_optab, TYPE_MODE (type));
+    op = usmul_widen_optab;
+
+  handler = widening_optab_handler (op, to_mode, from_mode);
 
   if (handler == CODE_FOR_nothing)
     return false;
@@ -2090,6 +2097,7 @@  convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple stmt,
   enum tree_code rhs1_code = ERROR_MARK, rhs2_code = ERROR_MARK;
   optab this_optab;
   enum tree_code wmult_code;
+  enum insn_code handler;
 
   lhs = gimple_assign_lhs (stmt);
   type = TREE_TYPE (lhs);
@@ -2163,7 +2171,8 @@  convert_plusminus_to_widen (gimple_stmt_iterator *gsi, gimple stmt,
      accumulate in this mode/signedness combination, otherwise
      this transformation is likely to pessimize code.  */
   this_optab = optab_for_tree_code (wmult_code, type1, optab_default);
-  if (optab_handler (this_optab, TYPE_MODE (type)) == CODE_FOR_nothing)
+  if (widening_optab_handler (this_optab, TYPE_MODE (type), TYPE_MODE (type1))
+	== CODE_FOR_nothing)
     return false;
 
   /* ??? May need some type verification here?  */