[gcc r12-1309] Improve match_simplify_replacement in phi-opt

[gcc r12-1309] Improve match_simplify_replacement in phi-opt

[Andrew Pinski]

https://gcc.gnu.org/g:c4574d23cb07340918793a5a98ae7bb2988b3791

commit r12-1309-gc4574d23cb07340918793a5a98ae7bb2988b3791
Author: Andrew Pinski <apinski@marvell.com>
Date:   Tue Jun 1 06:48:05 2021 +0000

    Improve match_simplify_replacement in phi-opt
    
    This improves match_simplify_replace in phi-opt to handle the
    case where there is one cheap (non-call) preparation statement in the
    middle basic block similar to xor_replacement and others.
    This allows to remove xor_replacement which it does too.
    
    OK?  Bootstrapped and tested on x86_64-linux-gnu with no regressions.
    
    Thanks,
    Andrew Pinski
    
    Changes since v1:
    v3 - Just minor changes to using gimple_assign_lhs
    instead of gimple_lhs and fixing a comment.
    v2 - change the check on the preparation statement to
    allow only assignments and no calls and only assignments
    that feed into the phi.
    
    gcc/ChangeLog:
    
            PR tree-optimization/25290
            * tree-ssa-phiopt.c (xor_replacement): Delete.
            (tree_ssa_phiopt_worker): Delete use of xor_replacement.
            (match_simplify_replacement): Allow one cheap preparation
            statement that can be moved to before the if.
    
    gcc/testsuite/ChangeLog:
    
            * gcc.dg/tree-ssa/pr96928-1.c: Fix testcase for now that ~
            happens on the outside of the bit_xor.

Diff:
---
 gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c |   4 +-
 gcc/tree-ssa-phiopt.c                     | 164 ++++++++++--------------------
 2 files changed, 54 insertions(+), 114 deletions(-)

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
index a2770e5e896..2e86620da11 100644
--- a/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr96928-1.c
@@ -1,9 +1,9 @@
 /* PR tree-optimization/96928 */
 /* { dg-do compile } */
-/* { dg-options "-O2 -fdump-tree-phiopt2" } */
+/* { dg-options "-O2 -fdump-tree-phiopt2 -fdump-tree-optimized" } */
 /* { dg-final { scan-tree-dump-times " = a_\[0-9]*\\\(D\\\) >> " 5 "phiopt2" } } */
 /* { dg-final { scan-tree-dump-times " = ~c_\[0-9]*\\\(D\\\);" 1 "phiopt2" } } */
-/* { dg-final { scan-tree-dump-times " = ~" 1 "phiopt2" } } */
+/* { dg-final { scan-tree-dump-times " = ~" 1 "optimized" } } */
 /* { dg-final { scan-tree-dump-times " = \[abc_0-9\\\(\\\)D]* \\\^ " 5 "phiopt2" } } */
 /* { dg-final { scan-tree-dump-not "a < 0" "phiopt2" } } */
 
diff --git a/gcc/tree-ssa-phiopt.c b/gcc/tree-ssa-phiopt.c
index 969b868397e..76f4e7ec843 100644
--- a/gcc/tree-ssa-phiopt.c
+++ b/gcc/tree-ssa-phiopt.c
@@ -28,6 +28,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "cfghooks.h"
 #include "tree-pass.h"
 #include "ssa.h"
+#include "tree-ssa.h"
 #include "optabs-tree.h"
 #include "insn-config.h"
 #include "gimple-pretty-print.h"
@@ -63,8 +64,6 @@ static bool minmax_replacement (basic_block, basic_block,
 				edge, edge, gphi *, tree, tree);
 static bool abs_replacement (basic_block, basic_block,
 			     edge, edge, gphi *, tree, tree);
-static bool xor_replacement (basic_block, basic_block,
-			     edge, edge, gphi *, tree, tree);
 static bool spaceship_replacement (basic_block, basic_block,
 				   edge, edge, gphi *, tree, tree);
 static bool cond_removal_in_popcount_clz_ctz_pattern (basic_block, basic_block,
@@ -352,9 +351,6 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads, bool early_p)
 	    cfgchanged = true;
 	  else if (abs_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
 	    cfgchanged = true;
-	  else if (!early_p
-		   && xor_replacement (bb, bb1, e1, e2, phi, arg0, arg1))
-	    cfgchanged = true;
 	  else if (!early_p
 		   && cond_removal_in_popcount_clz_ctz_pattern (bb, bb1, e1,
 								e2, phi, arg0,
@@ -801,14 +797,51 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
   edge true_edge, false_edge;
   gimple_seq seq = NULL;
   tree result;
-
-  if (!empty_block_p (middle_bb))
-    return false;
+  gimple *stmt_to_move = NULL;
 
   /* Special case A ? B : B as this will always simplify to B. */
   if (operand_equal_for_phi_arg_p (arg0, arg1))
     return false;
 
+  /* If the basic block only has a cheap preparation statement,
+     allow it and move it once the transformation is done. */
+  if (!empty_block_p (middle_bb))
+    {
+      stmt_to_move = last_and_only_stmt (middle_bb);
+      if (!stmt_to_move)
+	return false;
+
+      if (gimple_vuse (stmt_to_move))
+	return false;
+
+      if (gimple_could_trap_p (stmt_to_move)
+	  || gimple_has_side_effects (stmt_to_move))
+	return false;
+
+      if (gimple_uses_undefined_value_p (stmt_to_move))
+	return false;
+
+      /* Allow assignments and not no calls.
+	 As const calls don't match any of the above, yet they could
+	 still have some side-effects - they could contain
+	 gimple_could_trap_p statements, like floating point
+	 exceptions or integer division by zero.  See PR70586.
+	 FIXME: perhaps gimple_has_side_effects or gimple_could_trap_p
+	 should handle this.  */
+      if (!is_gimple_assign (stmt_to_move))
+	return false;
+
+      tree lhs = gimple_assign_lhs  (stmt_to_move);
+      gimple *use_stmt;
+      use_operand_p use_p;
+
+      /* Allow only a statement which feeds into the phi.  */
+      if (!lhs || TREE_CODE (lhs) != SSA_NAME
+	  || !single_imm_use (lhs, &use_p, &use_stmt)
+	  || use_stmt != phi)
+	return false;
+    }
+
     /* At this point we know we have a GIMPLE_COND with two successors.
      One successor is BB, the other successor is an empty block which
      falls through into BB.
@@ -844,7 +877,17 @@ match_simplify_replacement (basic_block cond_bb, basic_block middle_bb,
     return false;
 
   gsi = gsi_last_bb (cond_bb);
-
+  if (stmt_to_move)
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "statement un-sinked:\n");
+	  print_gimple_stmt (dump_file, stmt_to_move, 0,
+			   TDF_VOPS|TDF_MEMSYMS);
+	}
+      gimple_stmt_iterator gsi1 = gsi_for_stmt (stmt_to_move);
+      gsi_move_before (&gsi1, &gsi);
+    }
   if (seq)
     gsi_insert_seq_before (&gsi, seq, GSI_SAME_STMT);
 
@@ -2592,109 +2635,6 @@ abs_replacement (basic_block cond_bb, basic_block middle_bb,
   return true;
 }
 
-/* Optimize x < 0 ? ~y : y into (x >> (prec-1)) ^ y.  */
-
-static bool
-xor_replacement (basic_block cond_bb, basic_block middle_bb,
-		 edge e0 ATTRIBUTE_UNUSED, edge e1,
-		 gphi *phi, tree arg0, tree arg1)
-{
-  if (!INTEGRAL_TYPE_P (TREE_TYPE (arg1)))
-    return false;
-
-  /* OTHER_BLOCK must have only one executable statement which must have the
-     form arg0 = ~arg1 or arg1 = ~arg0.  */
-
-  gimple *assign = last_and_only_stmt (middle_bb);
-  /* If we did not find the proper one's complement assignment, then we cannot
-     optimize.  */
-  if (assign == NULL)
-    return false;
-
-  /* If we got here, then we have found the only executable statement
-     in OTHER_BLOCK.  If it is anything other than arg = ~arg1 or
-     arg1 = ~arg0, then we cannot optimize.  */
-  if (!is_gimple_assign (assign))
-    return false;
-
-  if (gimple_assign_rhs_code (assign) != BIT_NOT_EXPR)
-    return false;
-
-  tree lhs = gimple_assign_lhs (assign);
-  tree rhs = gimple_assign_rhs1 (assign);
-
-  /* The assignment has to be arg0 = -arg1 or arg1 = -arg0.  */
-  if (!(lhs == arg0 && rhs == arg1) && !(lhs == arg1 && rhs == arg0))
-    return false;
-
-  gimple *cond = last_stmt (cond_bb);
-  tree result = PHI_RESULT (phi);
-
-  /* Only relationals comparing arg[01] against zero are interesting.  */
-  enum tree_code cond_code = gimple_cond_code (cond);
-  if (cond_code != LT_EXPR && cond_code != GE_EXPR)
-    return false;
-
-  /* Make sure the conditional is x OP 0.  */
-  tree clhs = gimple_cond_lhs (cond);
-  if (TREE_CODE (clhs) != SSA_NAME
-      || !INTEGRAL_TYPE_P (TREE_TYPE (clhs))
-      || TYPE_UNSIGNED (TREE_TYPE (clhs))
-      || TYPE_PRECISION (TREE_TYPE (clhs)) != TYPE_PRECISION (TREE_TYPE (arg1))
-      || !integer_zerop (gimple_cond_rhs (cond)))
-    return false;
-
-  /* We need to know which is the true edge and which is the false
-     edge so that we know if have xor or inverted xor.  */
-  edge true_edge, false_edge;
-  extract_true_false_edges_from_block (cond_bb, &true_edge, &false_edge);
-
-  /* For GE_EXPR, if the true edge goes to OTHER_BLOCK, then we
-     will need to invert the result.  Similarly for LT_EXPR if
-     the false edge goes to OTHER_BLOCK.  */
-  edge e;
-  if (cond_code == GE_EXPR)
-    e = true_edge;
-  else
-    e = false_edge;
-
-  bool invert = e->dest == middle_bb;
-
-  result = duplicate_ssa_name (result, NULL);
-
-  gimple_stmt_iterator gsi = gsi_last_bb (cond_bb);
-
-  int prec = TYPE_PRECISION (TREE_TYPE (clhs));
-  gimple *new_stmt
-    = gimple_build_assign (make_ssa_name (TREE_TYPE (clhs)), RSHIFT_EXPR, clhs,
-			   build_int_cst (integer_type_node, prec - 1));
-  gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
-
-  if (!useless_type_conversion_p (TREE_TYPE (result), TREE_TYPE (clhs)))
-    {
-      new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
-				      NOP_EXPR, gimple_assign_lhs (new_stmt));
-      gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
-    }
-  lhs = gimple_assign_lhs (new_stmt);
-
-  if (invert)
-    {
-      new_stmt = gimple_build_assign (make_ssa_name (TREE_TYPE (result)),
-				      BIT_NOT_EXPR, rhs);
-      gsi_insert_before (&gsi, new_stmt, GSI_SAME_STMT);
-      rhs = gimple_assign_lhs (new_stmt);
-    }
-
-  new_stmt = gimple_build_assign (result, BIT_XOR_EXPR, lhs, rhs);
-  gsi_insert_before (&gsi, new_stmt, GSI_NEW_STMT);
-
-  replace_phi_edge_with_variable (cond_bb, e1, phi, result);
-
-  /* Note that we optimized this PHI.  */
-  return true;
-}
-
 /* Auxiliary functions to determine the set of memory accesses which
    can't trap because they are preceded by accesses to the same memory
    portion.  We do that for MEM_REFs, so we only need to track