Hi!
This patch optimizes a = {}; b = a; into a = {}; b = {};
and similarly for memset instead of the first stmt and/or memcpy
instead of the second one.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2016-11-25 Jakub Jelinek <ja...@redhat.com>
PR c/78408
* tree-ssa-ccp.c: Include tree-dfa.h.
(optimize_memcpy): New function.
(pass_fold_builtins::execute): Use it. Remove useless conditional
break after BUILT_IN_VA_*.
* gcc.dg/pr78408.c: New test.
--- gcc/tree-ssa-ccp.c.jj 2016-11-18 20:04:27.000000000 +0100
+++ gcc/tree-ssa-ccp.c 2016-11-25 17:54:26.862166658 +0100
@@ -143,6 +143,7 @@ along with GCC; see the file COPYING3.
#include "stor-layout.h"
#include "optabs-query.h"
#include "tree-ssa-ccp.h"
+#include "tree-dfa.h"
/* Possible lattice values. */
typedef enum
@@ -2928,6 +2929,113 @@ optimize_atomic_bit_test_and (gimple_stm
release_ssa_name (lhs);
}
+/* Optimize
+ a = {};
+ b = a;
+ into
+ a = {};
+ b = {};
+ Similarly for memset (&a, ..., sizeof (a)); instead of a = {};
+ and/or memcpy (&b, &a, sizeof (a)); instead of b = a; */
+
+static void
+optimize_memcpy (gimple_stmt_iterator *gsip, tree dest, tree src)
+{
+ gimple *stmt = gsi_stmt (*gsip);
+ if (gimple_has_volatile_ops (stmt)
+ || TREE_THIS_VOLATILE (dest)
+ || TREE_THIS_VOLATILE (src))
+ return;
+
+ tree vuse = gimple_vuse (stmt);
+ if (vuse == NULL)
+ return;
+
+ gimple *defstmt = SSA_NAME_DEF_STMT (vuse);
+ tree src2 = NULL_TREE;
+ tree val = integer_zero_node;
+ if (gimple_store_p (defstmt)
+ && gimple_assign_single_p (defstmt)
+ && TREE_CODE (gimple_assign_rhs1 (defstmt)) == CONSTRUCTOR
+ && CONSTRUCTOR_NELTS (gimple_assign_rhs1 (defstmt)) == 0
+ && !gimple_clobber_p (defstmt))
+ src2 = gimple_assign_lhs (defstmt);
+ else if (gimple_call_builtin_p (defstmt, BUILT_IN_MEMSET)
+ && TREE_CODE (gimple_call_arg (defstmt, 0)) == ADDR_EXPR
+ && TREE_CODE (gimple_call_arg (defstmt, 1)) == INTEGER_CST
+ && TREE_CODE (gimple_call_arg (defstmt, 2)) == INTEGER_CST)
+ {
+ HOST_WIDE_INT ssize, max_size, off;
+ bool reverse;
+ src2 = TREE_OPERAND (gimple_call_arg (defstmt, 0), 0);
+ get_ref_base_and_extent (src2, &off, &ssize, &max_size, &reverse);
+ if (ssize != max_size
+ || (ssize % BITS_PER_UNIT) != 0
+ || !wi::eq_p (gimple_call_arg (defstmt, 2), ssize / BITS_PER_UNIT))
+ src2 = NULL_TREE;
+ else
+ {
+ val = gimple_call_arg (defstmt, 1);
+ if (!integer_zerop (val) && is_gimple_assign (stmt))
+ src2 = NULL_TREE;
+ }
+ }
+
+ if (src2 == NULL_TREE)
+ return;
+
+ if (!operand_equal_p (src, src2, 0))
+ {
+ /* Handle also
+ a = {};
+ MEM[(char * {ref-all})&b] = MEM[(char * {ref-all})&a]; */
+ if (is_gimple_assign (stmt)
+ && TREE_CODE (src) == MEM_REF
+ && integer_zerop (TREE_OPERAND (src, 1))
+ && TREE_CODE (TREE_OPERAND (src, 0)) == ADDR_EXPR
+ && DECL_P (src2)
+ && operand_equal_p (TREE_OPERAND (TREE_OPERAND (src, 0), 0),
+ src2, 0)
+ && tree_int_cst_equal (TYPE_SIZE (TREE_TYPE (src)),
+ DECL_SIZE (src2)))
+ src = TREE_OPERAND (TREE_OPERAND (src, 0), 0);
+ else
+ return;
+ }
+ if (refs_may_alias_p (dest, src))
+ return;
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "Simplified\n ");
+ print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+ fprintf (dump_file, "after previous\n ");
+ print_gimple_stmt (dump_file, defstmt, 0, dump_flags);
+ }
+
+ if (is_gimple_assign (stmt))
+ {
+ tree ctor = build_constructor (TREE_TYPE (dest), NULL);
+ gimple_assign_set_rhs_from_tree (gsip, ctor);
+ update_stmt (stmt);
+ }
+ else
+ {
+ gcall *call = as_a <gcall *> (stmt);
+ tree fndecl = builtin_decl_implicit (BUILT_IN_MEMSET);
+ gimple_call_set_fndecl (call, fndecl);
+ gimple_call_set_fntype (call, TREE_TYPE (fndecl));
+ gimple_call_set_arg (call, 1, val);
+ update_stmt (stmt);
+ }
+
+ if (dump_file && (dump_flags & TDF_DETAILS))
+ {
+ fprintf (dump_file, "into\n ");
+ print_gimple_stmt (dump_file, stmt, 0, dump_flags);
+ }
+}
+
/* A simple pass that attempts to fold all builtin functions. This pass
is run after we've propagated as many constants as we can. */
@@ -2994,6 +3102,9 @@ pass_fold_builtins::execute (function *f
continue;
}
}
+ else if (gimple_assign_load_p (stmt) && gimple_store_p (stmt))
+ optimize_memcpy (&i, gimple_assign_lhs (stmt),
+ gimple_assign_rhs1 (stmt));
gsi_next (&i);
continue;
}
@@ -3109,14 +3220,39 @@ pass_fold_builtins::execute (function *f
false, false);
break;
+ case BUILT_IN_MEMCPY:
+ if (gimple_call_builtin_p (stmt, BUILT_IN_NORMAL)
+ && TREE_CODE (gimple_call_arg (stmt, 0)) == ADDR_EXPR
+ && TREE_CODE (gimple_call_arg (stmt, 1)) == ADDR_EXPR
+ && TREE_CODE (gimple_call_arg (stmt, 2)) == INTEGER_CST)
+ {
+ tree dest = TREE_OPERAND (gimple_call_arg (stmt, 0), 0);
+ tree src = TREE_OPERAND (gimple_call_arg (stmt, 1), 0);
+ HOST_WIDE_INT dsize, ssize, max_size, off;
+ bool reverse;
+ get_ref_base_and_extent (dest, &off, &dsize, &max_size,
+ &reverse);
+ if (dsize != max_size)
+ break;
+ get_ref_base_and_extent (src, &off, &ssize, &max_size,
+ &reverse);
+ if (ssize != max_size
+ || ssize != dsize
+ || (ssize % BITS_PER_UNIT) != 0)
+ break;
+ if (!wi::eq_p (gimple_call_arg (stmt, 2),
+ ssize / BITS_PER_UNIT))
+ break;
+ optimize_memcpy (&i, dest, src);
+ }
+ break;
+
case BUILT_IN_VA_START:
case BUILT_IN_VA_END:
case BUILT_IN_VA_COPY:
/* These shouldn't be folded before pass_stdarg. */
result = optimize_stdarg_builtin (stmt);
- if (result)
- break;
- /* FALLTHRU */
+ break;
default:;
}
--- gcc/testsuite/gcc.dg/pr78408.c.jj 2016-11-25 18:02:47.344752199 +0100
+++ gcc/testsuite/gcc.dg/pr78408.c 2016-11-25 18:02:26.000000000 +0100
@@ -0,0 +1,78 @@
+/* PR c/78408 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-fab1-details" } */
+/* { dg-final { scan-tree-dump-times "after previous" 16 "fab1" } } */
+
+struct S { char a[32]; };
+struct T { char a[65536]; };
+void bar (int, struct S *, struct S *, struct T *, struct T *);
+
+void
+f1 (void)
+{
+ struct S a, b;
+ struct T c, d;
+ a = b = (struct S) {};
+ c = d = (struct T) {};
+ bar (1, &a, &b, &c, &d);
+}
+
+void
+f2 (void)
+{
+ struct S a, b;
+ struct T c, d;
+ b = (struct S) {};
+ a = b;
+ d = (struct T) {};
+ c = d;
+ bar (2, &a, &b, &c, &d);
+}
+
+void
+f3 (void)
+{
+ struct S a, b;
+ struct T c, d;
+ __builtin_memset (&b, 0, sizeof (b));
+ a = b;
+ __builtin_memset (&d, 0, sizeof (d));
+ c = d;
+ bar (3, &a, &b, &c, &d);
+}
+
+
+void
+f4 (void)
+{
+ struct S a, b;
+ struct T c, d;
+ b = (struct S) {};
+ __builtin_memcpy (&a, &b, sizeof (b));
+ d = (struct T) {};
+ __builtin_memcpy (&c, &d, sizeof (d));
+ bar (4, &a, &b, &c, &d);
+}
+
+void
+f5 (void)
+{
+ struct S a, b;
+ struct T c, d;
+ __builtin_memset (&b, 0, sizeof (b));
+ __builtin_memcpy (&a, &b, sizeof (b));
+ __builtin_memset (&d, 0, sizeof (d));
+ __builtin_memcpy (&c, &d, sizeof (d));
+ bar (5, &a, &b, &c, &d);
+}
+
+void
+f6 (void)
+{
+ struct S a, b, e, g;
+ struct T c, d, f, h;
+ g = e = a = b = (struct S) {};
+ h = f = c = d = (struct T) {};
+ bar (6, &a, &b, &c, &d);
+ bar (6, &e, &g, &f, &h);
+}
Jakub
