reassoc: Reassociate integral multiplies [PR95867]

For floating point multiply, we have nice code in reassoc to reassociate
multiplications to almost optimal sequence of as few multiplications as
possible (or library call), but for integral types we just give up
because there is no __builtin_powi* for those types.

As there is no library routine we could use, instead of adding new internal
call just to hold it temporarily and then lower to multiplications again,
this patch for the integral types calls into the sincos pass routine that
expands it into multiplications right away.

2021-01-11  Jakub Jelinek  <jakub@redhat.com>

	PR tree-optimization/95867
	* tree-ssa-math-opts.h: New header.
	* tree-ssa-math-opts.c: Include tree-ssa-math-opts.h.
	(powi_as_mults): No longer static.  Use build_one_cst instead of
	build_real.  Formatting fix.
	* tree-ssa-reassoc.c: Include tree-ssa-math-opts.h.
	(attempt_builtin_powi): Handle multiplication reassociation without
	powi_fndecl using powi_as_mults.
	(reassociate_bb): For integral types don't require
	-funsafe-math-optimizations to call attempt_builtin_powi.

	* gcc.dg/tree-ssa/pr95867.c: New test.

diff --git a/gcc/testsuite/gcc.dg/tree-ssa/pr95867.c b/gcc/testsuite/gcc.dg/tree-ssa/pr95867.c
new file mode 100644 (file)
index 0000000..8ab3690
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/tree-ssa/pr95867.c
@@ -0,0 +1,14 @@
+/* PR tree-optimization/95867 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+/* { dg-final { scan-tree-dump-times " \\* " 13 "optimized" } } */
+
+#define A n * n * n * n * n * n * n * n
+#define B A * A * A * A * A * A * A * A
+#define C B * B * B * B * B * B * B * B
+
+unsigned
+foo (unsigned n)
+{
+  return C * B * B * A * n * n * n * n * n;
+}

diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 91ec0f6fe8328acb2ce7fb151841348f0b13f7f6..74a16b66223d07726a898d9101d7f2af8777c603 100644 (file)
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -115,6 +115,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "tree-eh.h"
 #include "targhooks.h"
 #include "domwalk.h"
+#include "tree-ssa-math-opts.h"
 
 /* This structure represents one basic block that either computes a
    division, or is a common dominator for basic block that compute a
@@ -1527,7 +1528,7 @@ powi_as_mults_1 (gimple_stmt_iterator *gsi, location_t loc, tree type,
 /* Convert ARG0**N to a tree of multiplications of ARG0 with itself.
    This function needs to be kept in sync with powi_cost above.  */
 
-static tree
+tree
 powi_as_mults (gimple_stmt_iterator *gsi, location_t loc,
               tree arg0, HOST_WIDE_INT n)
 {
@@ -1536,9 +1537,9 @@ powi_as_mults (gimple_stmt_iterator *gsi, location_t loc,
   tree target;
 
   if (n == 0)
-    return build_real (type, dconst1);
+    return build_one_cst (type);
 
-  memset (cache, 0,  sizeof (cache));
+  memset (cache, 0, sizeof (cache));
   cache[1] = arg0;
 
   result = powi_as_mults_1 (gsi, loc, type, (n < 0) ? -n : n, cache);

diff --git a/gcc/tree-ssa-math-opts.h b/gcc/tree-ssa-math-opts.h
new file mode 100644 (file)
index 0000000..37c666a
--- /dev/null
+++ b/gcc/tree-ssa-math-opts.h
@@ -0,0 +1,26 @@
+/* Global, SSA-based optimizations using mathematical identities.
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */
+
+#ifndef GCC_TREE_SSA_MATH_OPTS_H
+#define GCC_TREE_SSA_MATH_OPTS_H
+
+extern tree powi_as_mults (gimple_stmt_iterator *, location_t,
+                          tree, HOST_WIDE_INT);
+
+#endif  /* GCC_TREE_SSA_MATH_OPTS_H  */

diff --git a/gcc/tree-ssa-reassoc.c b/gcc/tree-ssa-reassoc.c
index fac74a3d83c50867223bafec62dce71f8416e59f..b6a09e5d9aa045a8f263b0824258441cdfe8a7f7 100644 (file)
--- a/gcc/tree-ssa-reassoc.c
+++ b/gcc/tree-ssa-reassoc.c
@@ -52,6 +52,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimplify.h"
 #include "case-cfn-macros.h"
 #include "tree-ssa-reassoc.h"
+#include "tree-ssa-math-opts.h"
 
 /*  This is a simple global reassociation pass.  It is, in part, based
     on the LLVM pass of the same name (They do some things more/less
@@ -5976,8 +5977,8 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
   gimple *mul_stmt, *pow_stmt;
 
   /* Nothing to do if BUILT_IN_POWI doesn't exist for this type and
-     target.  */
-  if (!powi_fndecl)
+     target, unless type is integral.  */
+  if (!powi_fndecl && !INTEGRAL_TYPE_P (type))
     return NULL_TREE;
 
   /* Allocate the repeated factor vector.  */
@@ -6086,14 +6087,33 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
            }
          else
            {
-             iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
-             pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr, 
-                                           build_int_cst (integer_type_node,
-                                                          power));
-             gimple_call_set_lhs (pow_stmt, iter_result);
-             gimple_set_location (pow_stmt, gimple_location (stmt));
-             gimple_set_uid (pow_stmt, gimple_uid (stmt));
-             gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
+             if (INTEGRAL_TYPE_P (type))
+               {
+                 gcc_assert (power > 1);
+                 gimple_stmt_iterator gsip = gsi;
+                 gsi_prev (&gsip);
+                 iter_result = powi_as_mults (&gsi, gimple_location (stmt),
+                                              rf1->repr, power);
+                 gimple_stmt_iterator gsic = gsi;
+                 while (gsi_stmt (gsic) != gsi_stmt (gsip))
+                   {
+                     gimple_set_uid (gsi_stmt (gsic), gimple_uid (stmt));
+                     gimple_set_visited (gsi_stmt (gsic), true);
+                     gsi_prev (&gsic);
+                   }
+               }
+             else
+               {
+                 iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
+                 pow_stmt
+                   = gimple_build_call (powi_fndecl, 2, rf1->repr,
+                                        build_int_cst (integer_type_node,
+                                                       power));
+                 gimple_call_set_lhs (pow_stmt, iter_result);
+                 gimple_set_location (pow_stmt, gimple_location (stmt));
+                 gimple_set_uid (pow_stmt, gimple_uid (stmt));
+                 gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
+               }
 
              if (dump_file && (dump_flags & TDF_DETAILS))
                {
@@ -6188,14 +6208,32 @@ attempt_builtin_powi (gimple *stmt, vec<operand_entry *> *ops)
          /* Form a call to __builtin_powi for the maximum product
             just formed, raised to the power obtained earlier.  */
          rf1 = &repeat_factor_vec[j];
-         iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
-         pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr, 
-                                       build_int_cst (integer_type_node,
-                                                      power));
-         gimple_call_set_lhs (pow_stmt, iter_result);
-         gimple_set_location (pow_stmt, gimple_location (stmt));
-         gimple_set_uid (pow_stmt, gimple_uid (stmt));
-         gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
+         if (INTEGRAL_TYPE_P (type))
+           {
+             gcc_assert (power > 1);
+             gimple_stmt_iterator gsip = gsi;
+             gsi_prev (&gsip);
+             iter_result = powi_as_mults (&gsi, gimple_location (stmt),
+                                          rf1->repr, power);
+             gimple_stmt_iterator gsic = gsi;
+             while (gsi_stmt (gsic) != gsi_stmt (gsip))
+               {
+                 gimple_set_uid (gsi_stmt (gsic), gimple_uid (stmt));
+                 gimple_set_visited (gsi_stmt (gsic), true);
+                 gsi_prev (&gsic);
+               }
+           }
+         else
+           {
+             iter_result = make_temp_ssa_name (type, NULL, "reassocpow");
+             pow_stmt = gimple_build_call (powi_fndecl, 2, rf1->repr,
+                                           build_int_cst (integer_type_node,
+                                                          power));
+             gimple_call_set_lhs (pow_stmt, iter_result);
+             gimple_set_location (pow_stmt, gimple_location (stmt));
+             gimple_set_uid (pow_stmt, gimple_uid (stmt));
+             gsi_insert_before (&gsi, pow_stmt, GSI_SAME_STMT);
+           }
        }
 
       /* If we previously formed at least one other builtin_powi call,
@@ -6522,7 +6560,8 @@ reassociate_bb (basic_block bb)
                  attempt_builtin_copysign (&ops);
 
                  if (reassoc_insert_powi_p
-                     && flag_unsafe_math_optimizations)
+                     && (flag_unsafe_math_optimizations
+                         || (INTEGRAL_TYPE_P (TREE_TYPE (lhs)))))
                    powi_result = attempt_builtin_powi (stmt, &ops);
                }