On Fri, 25 Nov 2016, Jakub Jelinek wrote:
> 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;
I wonder why you jump through the hoops of get_ref_base_and_extent
given the call args will be invariant addresses and thus
get_addr_base_and_unit_offset would be more appropriate here.
Also not sure why you want to restrict the size with the wi::eq_p
(probably for the a = b case where the size isn't given explicitely
but then you don't check whether off is 0 ...). I'd say passing
in base, offset and size for src and dest into this function will
simplify things and should allow to handle
memset (p+10, 0, 24);
memcpy (q, p+10, 24);
if you compare bases with operand_equal_p.
> + 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;
Why's that?
Richard.
> + 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
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
