re PR tree-optimization/71016 (Redundant sign extension with conditional __builtin_clzl)

PR tree-optimization/71016
	* tree-ssa-phiopt.c (tree_ssa_phiopt_worker): Pass cond_stmt to
	factor_out_conditional_conversion.  Formatting fix.
	(factor_out_conditional_conversion): Add cond_stmt argument.
	If arg1 is INTEGER_CST, punt if new_arg0 is not any operand of
	cond_stmt and if arg0_def_stmt is not the only stmt in its bb.
	Formatting fix.

	* gcc.target/i386/pr71016.c: New test.
	* gcc.target/aarch64/pr71016.c: New test.
	* gcc.dg/tree-ssa/pr66726-3.c: New test.

From-SVN: r244114

gcc/ChangeLog

@@ -1,3 +1,13 @@
+2017-01-05  Jakub Jelinek  <jakub@redhat.com>
+
+	PR tree-optimization/71016
+	* tree-ssa-phiopt.c (tree_ssa_phiopt_worker): Pass cond_stmt to
+	factor_out_conditional_conversion.  Formatting fix.
+	(factor_out_conditional_conversion): Add cond_stmt argument.
+	If arg1 is INTEGER_CST, punt if new_arg0 is not any operand of
+	cond_stmt and if arg0_def_stmt is not the only stmt in its bb.
+	Formatting fix.
+
 2017-01-05  David Malcolm  <dmalcolm@redhat.com>
 
 	* Makefile.in (OBJS): Add read-md.o, read-rtl.o,

gcc/testsuite/ChangeLog

@@ -1,5 +1,10 @@
 2017-01-05  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/71016
+	* gcc.target/i386/pr71016.c: New test.
+	* gcc.target/aarch64/pr71016.c: New test.
+	* gcc.dg/tree-ssa/pr66726-3.c: New test.
+
 	PR c++/78931
 	* g++.dg/cpp1z/decomp19.C: New test.
 

gcc/testsuite/gcc.dg/tree-ssa/pr66726-3.c

@@ -0,0 +1,16 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times "MIN_EXPR" 1 "optimized" } } */
+
+extern unsigned short mode_size[];
+
+int
+oof (int mode)
+{
+  int tem;
+  if (64 < mode_size[mode])
+    tem = 64;
+  else
+    tem = mode_size[mode];
+  return tem;
+}

gcc/testsuite/gcc.target/aarch64/pr71016.c

@@ -0,0 +1,10 @@
+/* PR tree-optimization/71016 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+/* { dg-final { scan-assembler-not "sxtw" } } */
+
+long int
+foo (long int i)
+{
+  return i == 0 ? 17 : __builtin_clzl (i);
+}

gcc/testsuite/gcc.target/i386/pr71016.c

@@ -0,0 +1,10 @@
+/* PR tree-optimization/71016 */
+/* { dg-do compile { target lp64 } } */
+/* { dg-options "-O2 -mlzcnt" } */
+/* { dg-final { scan-assembler-not "cltq" } } */
+
+long int
+foo (long int i)
+{
+  return i == 0 ? 17 : __builtin_clzl (i);
+}

gcc/tree-ssa-phiopt.c

@@ -49,7 +49,8 @@ along with GCC; see the file COPYING3.  If not see
 static unsigned int tree_ssa_phiopt_worker (bool, bool);
 static bool conditional_replacement (basic_block, basic_block,
 				     edge, edge, gphi *, tree, tree);
-static gphi *factor_out_conditional_conversion (edge, edge, gphi *, tree, tree);
+static gphi *factor_out_conditional_conversion (edge, edge, gphi *, tree, tree,
+						gimple *);
 static int value_replacement (basic_block, basic_block,
 			      edge, edge, gimple *, tree, tree);
 static bool minmax_replacement (basic_block, basic_block,
@@ -313,7 +314,8 @@ tree_ssa_phiopt_worker (bool do_store_elim, bool do_hoist_loads)
 	  gcc_assert (arg0 != NULL_TREE && arg1 != NULL_TREE);
 
 	  gphi *newphi = factor_out_conditional_conversion (e1, e2, phi,
-							    arg0, arg1);
+							    arg0, arg1,
+							    cond_stmt);
 	  if (newphi != NULL)
 	    {
 	      phi = newphi;
@@ -402,11 +404,12 @@ replace_phi_edge_with_variable (basic_block cond_block,
 
 /* PR66726: Factor conversion out of COND_EXPR.  If the arguments of the PHI
    stmt are CONVERT_STMT, factor out the conversion and perform the conversion
-   to the result of PHI stmt.  Return the newly-created PHI, if any.  */
+   to the result of PHI stmt.  COND_STMT is the controlling predicate.
+   Return the newly-created PHI, if any.  */
 
 static gphi *
 factor_out_conditional_conversion (edge e0, edge e1, gphi *phi,
-				   tree arg0, tree arg1)
+				   tree arg0, tree arg1, gimple *cond_stmt)
 {
   gimple *arg0_def_stmt = NULL, *arg1_def_stmt = NULL, *new_stmt;
   tree new_arg0 = NULL_TREE, new_arg1 = NULL_TREE;
@@ -472,7 +475,31 @@ factor_out_conditional_conversion (edge e0, edge e1, gphi *phi,
 	  && int_fits_type_p (arg1, TREE_TYPE (new_arg0)))
 	{
 	  if (gimple_assign_cast_p (arg0_def_stmt))
+	    {
+	      /* For the INTEGER_CST case, we are just moving the
+		 conversion from one place to another, which can often
+		 hurt as the conversion moves further away from the
+		 statement that computes the value.  So, perform this
+		 only if new_arg0 is an operand of COND_STMT, or
+		 if arg0_def_stmt is the only non-debug stmt in
+		 its basic block, because then it is possible this
+		 could enable further optimizations (minmax replacement
+		 etc.).  See PR71016.  */
+	      if (new_arg0 != gimple_cond_lhs (cond_stmt)
+		  && new_arg0 != gimple_cond_rhs (cond_stmt)
+		  && gimple_bb (arg0_def_stmt) == e0->src)
+		{
+		  gsi = gsi_for_stmt (arg0_def_stmt);
+		  gsi_prev_nondebug (&gsi);
+		  if (!gsi_end_p (gsi))
+		    return NULL;
+		  gsi = gsi_for_stmt (arg0_def_stmt);
+		  gsi_next_nondebug (&gsi);
+		  if (!gsi_end_p (gsi))
+		    return NULL;
+		}
 	      new_arg1 = fold_convert (TREE_TYPE (new_arg0), arg1);
+	    }
 	  else
 	    return NULL;
 	}