RE: [PATCH 1/2]middle-end: Add new tbranch optab to add support for bit-test-and-branch operations

[Tamar Christina <Tamar.Christina@arm.com>]

> > +/* Check to see if the supplied comparison in PTEST can be performed as a
> > +   bit-test-and-branch instead.  VAL must contain the original tree
> > +   expression of the non-zero operand which will be used to rewrite the
> > +   comparison in PTEST.
> > +
> > +   Returns TRUE if operation succeeds and returns updated PMODE and
> PTEST,
> > +   else FALSE.  */
> > +
> > +enum insn_code
> > +static validate_test_and_branch (tree val, rtx *ptest, machine_mode
> > +*pmode) {
> > +  if (!val || TREE_CODE (val) != SSA_NAME)
> > +    return CODE_FOR_nothing;
> > +
> > +  machine_mode mode = TYPE_MODE (TREE_TYPE (val));  rtx test =
> > + *ptest;
> > +
> > +  if (GET_CODE (test) != EQ && GET_CODE (test) != NE)
> > +    return CODE_FOR_nothing;
> > +
> > +  /* If the target supports the testbit comparison directly, great.
> > + */  auto icode = direct_optab_handler (tbranch_optab, mode);  if
> > + (icode == CODE_FOR_nothing)
> > +    return icode;
> > +
> > +  if (tree_zero_one_valued_p (val))
> > +    {
> > +      auto pos = BYTES_BIG_ENDIAN ? GET_MODE_BITSIZE (mode) - 1 : 0;
> 
> Does this work for BYTES_BIG_ENDIAN && !WORDS_BIG_ENDIAN and mode
> > word_mode?
> 

It does now. In this particular case all that matters is the bit ordering, so I've changed
It to BITS_BIG_ENDIAN.

Also during the review of the AArch64 optab Richard Sandiford wanted me to split the
optabs apart into two.  The reason is that a match_operator still gets the full RTL.

In the case of a tbranch the full RTL has an invalid comparison, so if a target doesn't implement
the hook correctly this would lead to incorrect code.  We've now moved the operator as part of
the name itself to avoid this.

Bootstrapped Regtested on aarch64-none-linux-gnu and no issues.

Ok for master?

Thanks,
Tamar

gcc/ChangeLog:

	* dojump.cc (do_jump): Pass along value.
	(do_jump_by_parts_greater_rtx): Likewise.
	(do_jump_by_parts_zero_rtx): Likewise.
	(do_jump_by_parts_equality_rtx): Likewise.
	(do_compare_rtx_and_jump): Likewise.
	(do_compare_and_jump): Likewise.
	* dojump.h (do_compare_rtx_and_jump): New.
	* optabs.cc (emit_cmp_and_jump_insn_1): Refactor to take optab to check.
	(validate_test_and_branch): New.
	(emit_cmp_and_jump_insns): Optiobally take a value, and when value is
	supplied then check if it's suitable for tbranch.
	* optabs.def (tbranch_eq$a4, tbranch_ne$a4): New.
	* doc/md.texi (tbranch_@var{op}@var{mode}4): Document it.
	* optabs.h (emit_cmp_and_jump_insns):
	* tree.h (tree_zero_one_valued_p): New.

--- inline copy of patch ---

diff --git a/gcc/doc/md.texi b/gcc/doc/md.texi
index d0a71ecbb806de3a6564c6ffe973fec5da5c597b..c6c4b13d756de28078a0a779876a00c614246914 100644
--- a/gcc/doc/md.texi
+++ b/gcc/doc/md.texi
@@ -6964,6 +6964,14 @@ case, you can and should make operand 1's predicate reject some operators
 in the @samp{cstore@var{mode}4} pattern, or remove the pattern altogether
 from the machine description.
 
+@cindex @code{tbranch_@var{op}@var{mode}4} instruction pattern
+@item @samp{tbranch_@var{op}@var{mode}4}
+Conditional branch instruction combined with a bit test-and-compare
+instruction. Operand 0 is a comparison operator.  Operand 1 is the
+operand of the comparison. Operand 2 is the bit position of Operand 1 to test.
+Operand 3 is the @code{code_label} to jump to. @var{op} is one of @var{eq} or
+@var{ne}.
+
 @cindex @code{cbranch@var{mode}4} instruction pattern
 @item @samp{cbranch@var{mode}4}
 Conditional branch instruction combined with a compare instruction.
diff --git a/gcc/dojump.h b/gcc/dojump.h
index e379cceb34bb1765cb575636e4c05b61501fc2cf..d1d79c490c420a805fe48d58740a79c1f25fb839 100644
--- a/gcc/dojump.h
+++ b/gcc/dojump.h
@@ -71,6 +71,10 @@ extern void jumpifnot (tree exp, rtx_code_label *label,
 extern void jumpifnot_1 (enum tree_code, tree, tree, rtx_code_label *,
 			 profile_probability);
 
+extern void do_compare_rtx_and_jump (rtx, rtx, enum rtx_code, int, tree,
+				     machine_mode, rtx, rtx_code_label *,
+				     rtx_code_label *, profile_probability);
+
 extern void do_compare_rtx_and_jump (rtx, rtx, enum rtx_code, int,
 				     machine_mode, rtx, rtx_code_label *,
 				     rtx_code_label *, profile_probability);
diff --git a/gcc/dojump.cc b/gcc/dojump.cc
index 2af0cd1aca3b6af13d5d8799094ee93f18022296..190324f36f1a31990f8c49bc8c0f45c23da5c31e 100644
--- a/gcc/dojump.cc
+++ b/gcc/dojump.cc
@@ -619,7 +619,7 @@ do_jump (tree exp, rtx_code_label *if_false_label,
 	}
       do_compare_rtx_and_jump (temp, CONST0_RTX (GET_MODE (temp)),
 			       NE, TYPE_UNSIGNED (TREE_TYPE (exp)),
-			       GET_MODE (temp), NULL_RTX,
+			       exp, GET_MODE (temp), NULL_RTX,
 			       if_false_label, if_true_label, prob);
     }
 
@@ -687,7 +687,7 @@ do_jump_by_parts_greater_rtx (scalar_int_mode mode, int unsignedp, rtx op0,
 
       /* All but high-order word must be compared as unsigned.  */
       do_compare_rtx_and_jump (op0_word, op1_word, code, (unsignedp || i > 0),
-			       word_mode, NULL_RTX, NULL, if_true_label,
+			       NULL, word_mode, NULL_RTX, NULL, if_true_label,
 			       prob);
 
       /* Emit only one comparison for 0.  Do not emit the last cond jump.  */
@@ -695,8 +695,8 @@ do_jump_by_parts_greater_rtx (scalar_int_mode mode, int unsignedp, rtx op0,
 	break;
 
       /* Consider lower words only if these are equal.  */
-      do_compare_rtx_and_jump (op0_word, op1_word, NE, unsignedp, word_mode,
-			       NULL_RTX, NULL, if_false_label,
+      do_compare_rtx_and_jump (op0_word, op1_word, NE, unsignedp, NULL,
+			       word_mode, NULL_RTX, NULL, if_false_label,
 			       prob.invert ());
     }
 
@@ -755,7 +755,7 @@ do_jump_by_parts_zero_rtx (scalar_int_mode mode, rtx op0,
 
   if (part != 0)
     {
-      do_compare_rtx_and_jump (part, const0_rtx, EQ, 1, word_mode,
+      do_compare_rtx_and_jump (part, const0_rtx, EQ, 1, NULL, word_mode,
 			       NULL_RTX, if_false_label, if_true_label, prob);
       return;
     }
@@ -766,7 +766,7 @@ do_jump_by_parts_zero_rtx (scalar_int_mode mode, rtx op0,
 
   for (i = 0; i < nwords; i++)
     do_compare_rtx_and_jump (operand_subword_force (op0, i, mode),
-                             const0_rtx, EQ, 1, word_mode, NULL_RTX,
+			     const0_rtx, EQ, 1, NULL, word_mode, NULL_RTX,
 			     if_false_label, NULL, prob);
 
   if (if_true_label)
@@ -809,8 +809,8 @@ do_jump_by_parts_equality_rtx (scalar_int_mode mode, rtx op0, rtx op1,
 
   for (i = 0; i < nwords; i++)
     do_compare_rtx_and_jump (operand_subword_force (op0, i, mode),
-                             operand_subword_force (op1, i, mode),
-                             EQ, 0, word_mode, NULL_RTX,
+			     operand_subword_force (op1, i, mode),
+			     EQ, 0, NULL, word_mode, NULL_RTX,
 			     if_false_label, NULL, prob);
 
   if (if_true_label)
@@ -962,6 +962,23 @@ do_compare_rtx_and_jump (rtx op0, rtx op1, enum rtx_code code, int unsignedp,
 			 rtx_code_label *if_false_label,
 			 rtx_code_label *if_true_label,
 			 profile_probability prob)
+{
+  do_compare_rtx_and_jump (op0, op1, code, unsignedp, NULL, mode, size,
+			  if_false_label, if_true_label, prob);
+}
+
+/* Like do_compare_and_jump but expects the values to compare as two rtx's.
+   The decision as to signed or unsigned comparison must be made by the caller.
+
+   If MODE is BLKmode, SIZE is an RTX giving the size of the objects being
+   compared.  */
+
+void
+do_compare_rtx_and_jump (rtx op0, rtx op1, enum rtx_code code, int unsignedp,
+			 tree val, machine_mode mode, rtx size,
+			 rtx_code_label *if_false_label,
+			 rtx_code_label *if_true_label,
+			 profile_probability prob)
 {
   rtx tem;
   rtx_code_label *dummy_label = NULL;
@@ -1177,8 +1194,10 @@ do_compare_rtx_and_jump (rtx op0, rtx op1, enum rtx_code code, int unsignedp,
 		    }
 		  else
 		    dest_label = if_false_label;
-                  do_compare_rtx_and_jump (op0, op1, first_code, unsignedp, mode,
-					   size, dest_label, NULL, first_prob);
+
+		  do_compare_rtx_and_jump (op0, op1, first_code, unsignedp,
+					   val, mode, size, dest_label, NULL,
+					   first_prob);
 		}
 	      /* For !and_them we want to split:
 		 if (x) goto t; // prob;
@@ -1192,8 +1211,9 @@ do_compare_rtx_and_jump (rtx op0, rtx op1, enum rtx_code code, int unsignedp,
               else
 		{
 		  profile_probability first_prob = prob.split (cprob);
-		  do_compare_rtx_and_jump (op0, op1, first_code, unsignedp, mode,
-					   size, NULL, if_true_label, first_prob);
+		  do_compare_rtx_and_jump (op0, op1, first_code, unsignedp,
+					   val, mode, size, NULL,
+					   if_true_label, first_prob);
 		  if (orig_code == NE && can_compare_p (UNEQ, mode, ccp_jump))
 		    {
 		      /* x != y can be split into x unord y || x ltgt y
@@ -1215,7 +1235,7 @@ do_compare_rtx_and_jump (rtx op0, rtx op1, enum rtx_code code, int unsignedp,
 	    }
 	}
 
-      emit_cmp_and_jump_insns (op0, op1, code, size, mode, unsignedp,
+      emit_cmp_and_jump_insns (op0, op1, code, size, mode, unsignedp, val,
 			       if_true_label, prob);
     }
 
@@ -1289,9 +1309,9 @@ do_compare_and_jump (tree treeop0, tree treeop1, enum rtx_code signed_code,
       op1 = new_op1;
     }
 
-  do_compare_rtx_and_jump (op0, op1, code, unsignedp, mode,
-                           ((mode == BLKmode)
-                            ? expr_size (treeop0) : NULL_RTX),
+  do_compare_rtx_and_jump (op0, op1, code, unsignedp, treeop0, mode,
+			   ((mode == BLKmode)
+			    ? expr_size (treeop0) : NULL_RTX),
 			   if_false_label, if_true_label, prob);
 }
 
diff --git a/gcc/optabs.cc b/gcc/optabs.cc
index 31b15fd3df5fa88119867a23d2abbed139a05115..303b4fd2def9278ddbc3d586103ac8274e73a982 100644
--- a/gcc/optabs.cc
+++ b/gcc/optabs.cc
@@ -46,6 +46,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "libfuncs.h"
 #include "internal-fn.h"
 #include "langhooks.h"
+#include "gimple.h"
+#include "ssa.h"
 
 static void prepare_float_lib_cmp (rtx, rtx, enum rtx_code, rtx *,
 				   machine_mode *);
@@ -4623,7 +4625,8 @@ prepare_operand (enum insn_code icode, rtx x, int opnum, machine_mode mode,
 
 static void
 emit_cmp_and_jump_insn_1 (rtx test, machine_mode mode, rtx label,
-			  profile_probability prob)
+			  direct_optab cmp_optab, profile_probability prob,
+			  bool test_branch)
 {
   machine_mode optab_mode;
   enum mode_class mclass;
@@ -4632,12 +4635,17 @@ emit_cmp_and_jump_insn_1 (rtx test, machine_mode mode, rtx label,
 
   mclass = GET_MODE_CLASS (mode);
   optab_mode = (mclass == MODE_CC) ? CCmode : mode;
-  icode = optab_handler (cbranch_optab, optab_mode);
+  icode = optab_handler (cmp_optab, optab_mode);
 
   gcc_assert (icode != CODE_FOR_nothing);
-  gcc_assert (insn_operand_matches (icode, 0, test));
-  insn = emit_jump_insn (GEN_FCN (icode) (test, XEXP (test, 0),
-                                          XEXP (test, 1), label));
+  gcc_assert (test_branch || insn_operand_matches (icode, 0, test));
+  if (test_branch)
+    insn = emit_jump_insn (GEN_FCN (icode) (XEXP (test, 0),
+					    XEXP (test, 1), label));
+  else
+    insn = emit_jump_insn (GEN_FCN (icode) (test, XEXP (test, 0),
+					    XEXP (test, 1), label));
+
   if (prob.initialized_p ()
       && profile_status_for_fn (cfun) != PROFILE_ABSENT
       && insn
@@ -4647,6 +4655,63 @@ emit_cmp_and_jump_insn_1 (rtx test, machine_mode mode, rtx label,
     add_reg_br_prob_note (insn, prob);
 }
 
+/* Check to see if the supplied comparison in PTEST can be performed as a
+   bit-test-and-branch instead.  VAL must contain the original tree
+   expression of the non-zero operand which will be used to rewrite the
+   comparison in PTEST.
+
+   Returns TRUE if operation succeeds and returns updated PMODE and PTEST,
+   else FALSE.  */
+
+static enum insn_code
+validate_test_and_branch (tree val, rtx *ptest, machine_mode *pmode, optab *res)
+{
+  if (!val || TREE_CODE (val) != SSA_NAME)
+    return CODE_FOR_nothing;
+
+  machine_mode mode = TYPE_MODE (TREE_TYPE (val));
+  rtx test = *ptest;
+  direct_optab optab;
+
+  if (GET_CODE (test) == EQ)
+    optab = tbranch_eq_optab;
+  else if (GET_CODE (test) == NE)
+    optab = tbranch_ne_optab;
+  else
+    return CODE_FOR_nothing;
+
+  *res = optab;
+
+  /* If the target supports the testbit comparison directly, great.  */
+  auto icode = direct_optab_handler (optab, mode);
+  if (icode == CODE_FOR_nothing)
+    return icode;
+
+  if (tree_zero_one_valued_p (val))
+    {
+      auto pos = BITS_BIG_ENDIAN ? GET_MODE_BITSIZE (mode) - 1 : 0;
+      XEXP (test, 1) = gen_int_mode (pos, mode);
+      *ptest = test;
+      *pmode = mode;
+      return icode;
+    }
+
+  wide_int wcst = get_nonzero_bits (val);
+  if (wcst == -1)
+    return CODE_FOR_nothing;
+
+  int bitpos;
+
+  if ((bitpos = wi::exact_log2 (wcst)) == -1)
+    return CODE_FOR_nothing;
+
+  auto pos = BITS_BIG_ENDIAN ? GET_MODE_BITSIZE (mode) - 1 - bitpos : bitpos;
+  XEXP (test, 1) = gen_int_mode (pos, mode);
+  *ptest = test;
+  *pmode = mode;
+  return icode;
+}
+
 /* Generate code to compare X with Y so that the condition codes are
    set and to jump to LABEL if the condition is true.  If X is a
    constant and Y is not a constant, then the comparison is swapped to
@@ -4664,11 +4729,13 @@ emit_cmp_and_jump_insn_1 (rtx test, machine_mode mode, rtx label,
    It will be potentially converted into an unsigned variant based on
    UNSIGNEDP to select a proper jump instruction.
    
-   PROB is the probability of jumping to LABEL.  */
+   PROB is the probability of jumping to LABEL.  If the comparison is against
+   zero then VAL contains the expression from which the non-zero RTL is
+   derived.  */
 
 void
 emit_cmp_and_jump_insns (rtx x, rtx y, enum rtx_code comparison, rtx size,
-			 machine_mode mode, int unsignedp, rtx label,
+			 machine_mode mode, int unsignedp, tree val, rtx label,
                          profile_probability prob)
 {
   rtx op0 = x, op1 = y;
@@ -4693,10 +4760,34 @@ emit_cmp_and_jump_insns (rtx x, rtx y, enum rtx_code comparison, rtx size,
 
   prepare_cmp_insn (op0, op1, comparison, size, unsignedp, OPTAB_LIB_WIDEN,
 		    &test, &mode);
-  emit_cmp_and_jump_insn_1 (test, mode, label, prob);
+
+  /* Check if we're comparing a truth type with 0, and if so check if
+     the target supports tbranch.  */
+  machine_mode tmode = mode;
+  direct_optab optab;
+  if (op1 == CONST0_RTX (GET_MODE (op1))
+      && validate_test_and_branch (val, &test, &tmode,
+				   &optab) != CODE_FOR_nothing)
+    {
+      emit_cmp_and_jump_insn_1 (test, tmode, label, optab, prob, true);
+      return;
+    }
+
+  emit_cmp_and_jump_insn_1 (test, mode, label, cbranch_optab, prob, false);
 }
 
-

+/* Overloaded version of emit_cmp_and_jump_insns in which VAL is unknown.  */
+
+void
+emit_cmp_and_jump_insns (rtx x, rtx y, enum rtx_code comparison, rtx size,
+			 machine_mode mode, int unsignedp, rtx label,
+			 profile_probability prob)
+{
+  emit_cmp_and_jump_insns (x, y, comparison, size, mode, unsignedp, NULL,
+			   label, prob);
+}
+
+
 /* Emit a library call comparison between floating point X and Y.
    COMPARISON is the rtl operator to compare with (EQ, NE, GT, etc.).  */
 
diff --git a/gcc/optabs.def b/gcc/optabs.def
index a6db2342bed6baf13ecbd84112c8432c6972e6fe..3199b05e90d6b9b9c6fb3c0353db3db02321e964 100644
--- a/gcc/optabs.def
+++ b/gcc/optabs.def
@@ -220,6 +220,8 @@ OPTAB_D (reload_in_optab, "reload_in$a")
 OPTAB_D (reload_out_optab, "reload_out$a")
 
 OPTAB_DC(cbranch_optab, "cbranch$a4", COMPARE)
+OPTAB_D (tbranch_eq_optab, "tbranch_eq$a4")
+OPTAB_D (tbranch_ne_optab, "tbranch_ne$a4")
 OPTAB_D (addcc_optab, "add$acc")
 OPTAB_D (negcc_optab, "neg$acc")
 OPTAB_D (notcc_optab, "not$acc")
diff --git a/gcc/optabs.h b/gcc/optabs.h
index cfd7c742d2d21b0539f5227c22a94f32c793d6f7..cd55604bc3d452d7e28c5530bb4793d481766f4f 100644
--- a/gcc/optabs.h
+++ b/gcc/optabs.h
@@ -268,6 +268,10 @@ extern void emit_cmp_and_jump_insns (rtx, rtx, enum rtx_code, rtx,
 				     machine_mode, int, rtx,
 				     profile_probability prob
 					= profile_probability::uninitialized ());
+extern void emit_cmp_and_jump_insns (rtx, rtx, enum rtx_code, rtx,
+				     machine_mode, int, tree, rtx,
+				     profile_probability prob
+					= profile_probability::uninitialized ());
 
 /* Generate code to indirectly jump to a location given in the rtx LOC.  */
 extern void emit_indirect_jump (rtx);
diff --git a/gcc/tree.h b/gcc/tree.h
index a863d2e50e5ecafa3f5da4dda98d9637261d07a9..abedaa80a3983ebb6f9ac733b2eaa8d039688f0a 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -4726,6 +4726,7 @@ extern tree signed_or_unsigned_type_for (int, tree);
 extern tree signed_type_for (tree);
 extern tree unsigned_type_for (tree);
 extern bool is_truth_type_for (tree, tree);
+extern bool tree_zero_one_valued_p (tree);
 extern tree truth_type_for (tree);
 extern tree build_pointer_type_for_mode (tree, machine_mode, bool);
 extern tree build_pointer_type (tree);