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-Date: Thu, 26 Oct 2006 23:27:59 +0200
-From: Jan Hubicka <jh at suse dot cz>
-To: gcc-patches at gcc dot gnu dot org
-Subject: More memcpy folding
-Message-ID: <20061026212759.GD6035@kam.mff.cuni.cz>
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-
-Hi,
-this patch extends Jakub's code to fold memcpy into assignment to case of
-structures to make GCC understand common low-level C idiom of
-memcpy (&a, &b, sizeof (*a))
-for copying structures. This is of less academic interested as my previous
-memmove folding since it matches quite few times during GCC bootstrap
-and during SPEC build. The transfomration often kills last place taking
-address of the argument thus allowing SRA and other optimizations.
-
-I tried to cover as many cases as possible. Unforutnately there are
-aliasing issues as shown by execute/20060930-2.c, so I need to check
-var_decl_component_p. With little help from PTA we should be probably
-able to do better here.
-
-Bootstrapped/regtested i686-linux, OK?
-:ADDPATCH middle-end:
-
-Honza
-
/* { dg-do compile } */
/* { dg-options "-O2 -fdump-tree-optimized" } */
/* { dg-final { scan-tree-dump-times "nasty_local" 0 "optimized" } } */
int test(struct a a)
{
struct a nasty_local;
-memcpy (&nasty_local,&a, sizeof(a));
+__builtin_memcpy (&nasty_local,&a, sizeof(a));
return nasty_local.a;
}
- * builtins.c: Include tree-flow.h.
- (fold_builtin_memory_op): Be more aggressive on converting memcpy to
- assignment; convert memmove to memcpy for sizes greater than 1 where
- alignment of operands prohibit the partial overlap.
-Index: builtins.c
-===================================================================
-*** builtins.c (revision 118067)
---- builtins.c (working copy)
-*************** Software Foundation, 51 Franklin Street,
-*** 47,52 ****
---- 47,53 ----
- #include "langhooks.h"
- #include "basic-block.h"
- #include "tree-mudflap.h"
-+ #include "tree-flow.h"
-
- #ifndef PAD_VARARGS_DOWN
- #define PAD_VARARGS_DOWN BYTES_BIG_ENDIAN
-*************** static tree
-*** 8029,8035 ****
- fold_builtin_memory_op (tree arglist, tree type, bool ignore, int endp)
- {
- tree dest, src, len, destvar, srcvar, expr;
-- unsigned HOST_WIDE_INT length;
-
- if (! validate_arglist (arglist,
- POINTER_TYPE, POINTER_TYPE, INTEGER_TYPE, VOID_TYPE))
---- 8030,8035 ----
-*************** fold_builtin_memory_op (tree arglist, tr
-*** 8049,8060 ****
- expr = len;
- else
- {
- if (endp == 3)
- {
-! unsigned int src_align
-! = get_pointer_alignment (src, BIGGEST_ALIGNMENT);
-! unsigned int dest_align
-! = get_pointer_alignment (dest, BIGGEST_ALIGNMENT);
- /* Both DEST and SRC must be pointer types.
- ??? This is what old code did. Is the testing for pointer types
- really mandatory?
---- 8049,8060 ----
- expr = len;
- else
- {
-+ tree srctype, desttype;
- if (endp == 3)
- {
-! int src_align = get_pointer_alignment (src, BIGGEST_ALIGNMENT);
-! int dest_align = get_pointer_alignment (dest, BIGGEST_ALIGNMENT);
-!
- /* Both DEST and SRC must be pointer types.
- ??? This is what old code did. Is the testing for pointer types
- really mandatory?
-*************** fold_builtin_memory_op (tree arglist, tr
-*** 8062,8125 ****
- If either SRC is readonly or length is 1, we can use memcpy. */
- if (dest_align && src_align
- && (readonly_data_expr (src)
-! || integer_onep (len)))
- {
- tree fn = implicit_built_in_decls[BUILT_IN_MEMCPY];
- if (!fn)
- return 0;
- return build_function_call_expr (fn, arglist);
- }
- }
-- if (! host_integerp (len, 1))
-- return 0;
--
-- if (TREE_SIDE_EFFECTS (dest) || TREE_SIDE_EFFECTS (src))
-- return 0;
--
-- destvar = dest;
-- STRIP_NOPS (destvar);
-- if (TREE_CODE (destvar) != ADDR_EXPR)
-- return 0;
--
-- destvar = TREE_OPERAND (destvar, 0);
-- if (TREE_THIS_VOLATILE (destvar))
-- return 0;
-
-! if (!INTEGRAL_TYPE_P (TREE_TYPE (destvar))
-! && !POINTER_TYPE_P (TREE_TYPE (destvar))
-! && !SCALAR_FLOAT_TYPE_P (TREE_TYPE (destvar)))
- return 0;
-!
-! if (! var_decl_component_p (destvar))
- return 0;
-
-! srcvar = src;
-! STRIP_NOPS (srcvar);
-! if (TREE_CODE (srcvar) != ADDR_EXPR)
-! return 0;
-
-! srcvar = TREE_OPERAND (srcvar, 0);
- if (TREE_THIS_VOLATILE (srcvar))
- return 0;
-!
-! if (!INTEGRAL_TYPE_P (TREE_TYPE (srcvar))
-! && !POINTER_TYPE_P (TREE_TYPE (srcvar))
-! && !SCALAR_FLOAT_TYPE_P (TREE_TYPE (srcvar)))
- return 0;
-
-! if (! var_decl_component_p (srcvar))
- return 0;
-!
-! length = tree_low_cst (len, 1);
-! if (GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (destvar))) != length
-! || get_pointer_alignment (dest, BIGGEST_ALIGNMENT) / BITS_PER_UNIT
-! < (int) length
-! || GET_MODE_SIZE (TYPE_MODE (TREE_TYPE (srcvar))) != length
-! || get_pointer_alignment (src, BIGGEST_ALIGNMENT) / BITS_PER_UNIT
-! < (int) length)
- return 0;
-
-! if ((INTEGRAL_TYPE_P (TREE_TYPE (srcvar))
- || POINTER_TYPE_P (TREE_TYPE (srcvar)))
- && (INTEGRAL_TYPE_P (TREE_TYPE (destvar))
- || POINTER_TYPE_P (TREE_TYPE (destvar))))
---- 8062,8133 ----
- If either SRC is readonly or length is 1, we can use memcpy. */
- if (dest_align && src_align
- && (readonly_data_expr (src)
-! || (host_integerp (len, 1)
-! && (MIN (src_align, dest_align) / BITS_PER_UNIT <=
-! tree_low_cst (len, 1)))))
- {
- tree fn = implicit_built_in_decls[BUILT_IN_MEMCPY];
- if (!fn)
- return 0;
- return build_function_call_expr (fn, arglist);
- }
-+ return 0;
- }
-
-! if (!host_integerp (len, 0))
- return 0;
-! /* FIXME:
-! This logic lose for arguments like (type *)malloc (sizeof (type)),
-! since we strip the casts of up to VOID return value from malloc.
-! Perhaps we ought to inherit type from non-VOID argument here? */
-! STRIP_NOPS (src);
-! STRIP_NOPS (dest);
-! srctype = TREE_TYPE (TREE_TYPE (src));
-! desttype = TREE_TYPE (TREE_TYPE (dest));
-! if (!srctype || !desttype
-! || !TYPE_SIZE_UNIT (srctype)
-! || !TYPE_SIZE_UNIT (desttype)
-! || TREE_CODE (TYPE_SIZE_UNIT (srctype)) != INTEGER_CST
-! || TREE_CODE (TYPE_SIZE_UNIT (desttype)) != INTEGER_CST
-! || !operand_equal_p (TYPE_SIZE_UNIT (srctype), len, 0)
-! || !operand_equal_p (TYPE_SIZE_UNIT (desttype), len, 0))
-! return 0;
-!
-! if (get_pointer_alignment (dest, BIGGEST_ALIGNMENT)
-! < (int) TYPE_ALIGN (desttype)
-! || (get_pointer_alignment (src, BIGGEST_ALIGNMENT)
-! < (int) TYPE_ALIGN (srctype)))
- return 0;
-
-! if (!ignore)
-! dest = builtin_save_expr (dest);
-
-! srcvar = build_fold_indirect_ref (src);
- if (TREE_THIS_VOLATILE (srcvar))
- return 0;
-! /* With memcpy, it is possible to bypass aliasing rules, so without
-! this check i. e. execute/20060930-2.c would be misoptimized, because
-! it use conflicting alias set to hold argument for the memcpy call.
-! This check is probably unnecesary with -fno-strict-aliasing.
-! Similarly for destvar. See also PR29286. */
-! if (!var_decl_component_p (srcvar)
-! /* Accept: memcpy (*char_var, "test", 1); that simplify
-! to char_var='t'; */
-! || is_gimple_min_invariant (srcvar)
-! || readonly_data_expr (src))
- return 0;
-
-! destvar = build_fold_indirect_ref (dest);
-! if (TREE_THIS_VOLATILE (destvar))
- return 0;
-! if (!var_decl_component_p (destvar))
- return 0;
-
-! if (srctype == desttype
-! || (in_ssa_p
-! && tree_ssa_useless_type_conversion_1 (desttype, srctype)))
-! expr = srcvar;
-! else if ((INTEGRAL_TYPE_P (TREE_TYPE (srcvar))
- || POINTER_TYPE_P (TREE_TYPE (srcvar)))
- && (INTEGRAL_TYPE_P (TREE_TYPE (destvar))
- || POINTER_TYPE_P (TREE_TYPE (destvar))))
-
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