Hi!
As discussed on IRC, this patch introduces two new attributes,
so that the C library (and other headers) have a way to
a) tell the compiler something about functions like aligned_alloc
or memalign
b) tell the compiler the alignment of pointers returned say by malloc
Ok for trunk if bootstrap/regtest passes?
2014-02-06 Jakub Jelinek <ja...@redhat.com>
PR middle-end/60092
* tree-ssa-ccp.c (surely_varying_stmt_p): Don't return true
if TYPE_ATTRIBUTES (gimple_call_fntype ()) contain
assume_aligned or alloc_align attributes.
(bit_value_alloc_assume_aligned_attribute): New function.
(evaluate_stmt): Handle calls to functions with
assume_aligned or alloc_align attributes.
* doc/extend.texi: Document assume_aligned and alloc_align
attributes.
c-family/
* c-common.c (handle_alloc_align_attribute,
handle_assume_aligned_attribute): New functions.
(c_common_attribute_table): Add alloc_align and assume_aligned
attributes.
testsuite/
* gcc.dg/attr-alloc_align-1.c: New test.
* gcc.dg/attr-alloc_align-2.c: New test.
* gcc.dg/attr-alloc_align-3.c: New test.
* gcc.dg/attr-assume_aligned-1.c: New test.
* gcc.dg/attr-assume_aligned-2.c: New test.
* gcc.dg/attr-assume_aligned-3.c: New test.
--- gcc/c-family/c-common.c.jj 2014-02-05 10:37:58.000000000 +0100
+++ gcc/c-family/c-common.c 2014-02-06 15:35:15.707333771 +0100
@@ -366,6 +366,8 @@ static tree handle_warn_unused_result_at
static tree handle_sentinel_attribute (tree *, tree, tree, int, bool *);
static tree handle_type_generic_attribute (tree *, tree, tree, int, bool *);
static tree handle_alloc_size_attribute (tree *, tree, tree, int, bool *);
+static tree handle_alloc_align_attribute (tree *, tree, tree, int, bool *);
+static tree handle_assume_aligned_attribute (tree *, tree, tree, int, bool *);
static tree handle_target_attribute (tree *, tree, tree, int, bool *);
static tree handle_optimize_attribute (tree *, tree, tree, int, bool *);
static tree ignore_attribute (tree *, tree, tree, int, bool *);
@@ -766,6 +768,10 @@ const struct attribute_spec c_common_att
handle_omp_declare_simd_attribute, false },
{ "omp declare target", 0, 0, true, false, false,
handle_omp_declare_target_attribute, false },
+ { "alloc_align", 1, 1, false, true, true,
+ handle_alloc_align_attribute, false },
+ { "assume_aligned", 1, 2, false, true, true,
+ handle_assume_aligned_attribute, false },
{ NULL, 0, 0, false, false, false, NULL, false }
};
@@ -8046,13 +8052,64 @@ handle_alloc_size_attribute (tree *node,
if (TREE_CODE (position) != INTEGER_CST
|| TREE_INT_CST_HIGH (position)
|| TREE_INT_CST_LOW (position) < 1
- || TREE_INT_CST_LOW (position) > arg_count )
+ || TREE_INT_CST_LOW (position) > arg_count)
{
warning (OPT_Wattributes,
"alloc_size parameter outside range");
*no_add_attrs = true;
return NULL_TREE;
}
+ }
+ return NULL_TREE;
+}
+
+/* Handle a "alloc_align" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_alloc_align_attribute (tree *node, tree ARG_UNUSED (name), tree args,
+ int, bool *no_add_attrs)
+{
+ unsigned arg_count = type_num_arguments (*node);
+ tree position = TREE_VALUE (args);
+ if (position && TREE_CODE (position) != IDENTIFIER_NODE
+ && TREE_CODE (position) != FUNCTION_DECL)
+ position = default_conversion (position);
+
+ if (TREE_CODE (position) != INTEGER_CST
+ || TREE_INT_CST_HIGH (position)
+ || TREE_INT_CST_LOW (position) < 1
+ || TREE_INT_CST_LOW (position) > arg_count)
+ {
+ warning (OPT_Wattributes,
+ "alloc_align parameter outside range");
+ *no_add_attrs = true;
+ return NULL_TREE;
+ }
+ return NULL_TREE;
+}
+
+/* Handle a "assume_aligned" attribute; arguments as in
+ struct attribute_spec.handler. */
+
+static tree
+handle_assume_aligned_attribute (tree *node, tree ARG_UNUSED (name), tree args,
+ int, bool *no_add_attrs)
+{
+ for (; args; args = TREE_CHAIN (args))
+ {
+ tree position = TREE_VALUE (args);
+ if (position && TREE_CODE (position) != IDENTIFIER_NODE
+ && TREE_CODE (position) != FUNCTION_DECL)
+ position = default_conversion (position);
+
+ if (TREE_CODE (position) != INTEGER_CST)
+ {
+ warning (OPT_Wattributes,
+ "assume_aligned parameter not integer constant");
+ *no_add_attrs = true;
+ return NULL_TREE;
+ }
}
return NULL_TREE;
}
--- gcc/tree-ssa-ccp.c.jj 2014-01-03 11:40:46.000000000 +0100
+++ gcc/tree-ssa-ccp.c 2014-02-06 16:16:27.260996887 +0100
@@ -738,13 +738,18 @@ surely_varying_stmt_p (gimple stmt)
return true;
/* If it is a call and does not return a value or is not a
- builtin and not an indirect call, it is varying. */
+ builtin and not an indirect call or a call to function with
+ assume_aligned/alloc_align attribute, it is varying. */
if (is_gimple_call (stmt))
{
- tree fndecl;
+ tree fndecl, fntype = gimple_call_fntype (stmt);
if (!gimple_call_lhs (stmt)
|| ((fndecl = gimple_call_fndecl (stmt)) != NULL_TREE
- && !DECL_BUILT_IN (fndecl)))
+ && !DECL_BUILT_IN (fndecl)
+ && !lookup_attribute ("assume_aligned",
+ TYPE_ATTRIBUTES (fntype))
+ && !lookup_attribute ("alloc_align",
+ TYPE_ATTRIBUTES (fntype))))
return true;
}
@@ -1534,6 +1539,77 @@ bit_value_assume_aligned (gimple stmt)
return val;
}
+/* Return the propagation value for functions with assume_aligned
+ or alloc_aligned attribute. */
+
+static prop_value_t
+bit_value_alloc_assume_aligned_attribute (gimple stmt, tree attr,
+ prop_value_t ptrval,
+ bool alloc_aligned)
+{
+ tree lhs = gimple_call_lhs (stmt), align, misalign = NULL_TREE;
+ tree type = TREE_TYPE (lhs);
+ unsigned HOST_WIDE_INT aligni, misaligni = 0;
+ prop_value_t alignval;
+ double_int value, mask;
+ prop_value_t val;
+ if (ptrval.lattice_val == UNDEFINED)
+ return ptrval;
+ gcc_assert ((ptrval.lattice_val == CONSTANT
+ && TREE_CODE (ptrval.value) == INTEGER_CST)
+ || ptrval.mask.is_minus_one ());
+ if (TREE_VALUE (attr) == NULL_TREE)
+ return ptrval;
+ attr = TREE_VALUE (attr);
+ align = TREE_VALUE (attr);
+ if (!tree_fits_uhwi_p (align))
+ return ptrval;
+ aligni = tree_to_uhwi (align);
+ if (alloc_aligned)
+ {
+ if (aligni == 0 || aligni > gimple_call_num_args (stmt))
+ return ptrval;
+ align = gimple_call_arg (stmt, aligni - 1);
+ if (!tree_fits_uhwi_p (align))
+ return ptrval;
+ aligni = tree_to_uhwi (align);
+ }
+ if (aligni <= 1
+ || (aligni & (aligni - 1)) != 0)
+ return ptrval;
+ if (!alloc_aligned && TREE_CHAIN (attr) && TREE_VALUE (TREE_CHAIN (attr)))
+ {
+ misalign = TREE_VALUE (TREE_CHAIN (attr));
+ if (!tree_fits_uhwi_p (misalign))
+ return ptrval;
+ misaligni = tree_to_uhwi (misalign);
+ if (misaligni >= aligni)
+ return ptrval;
+ }
+ align = build_int_cst_type (type, -aligni);
+ alignval = get_value_for_expr (align, true);
+ bit_value_binop_1 (BIT_AND_EXPR, type, &value, &mask,
+ type, value_to_double_int (ptrval), ptrval.mask,
+ type, value_to_double_int (alignval), alignval.mask);
+ if (!mask.is_minus_one ())
+ {
+ val.lattice_val = CONSTANT;
+ val.mask = mask;
+ gcc_assert ((mask.low & (aligni - 1)) == 0);
+ gcc_assert ((value.low & (aligni - 1)) == 0);
+ value.low |= misaligni;
+ /* ??? Delay building trees here. */
+ val.value = double_int_to_tree (type, value);
+ }
+ else
+ {
+ val.lattice_val = VARYING;
+ val.value = NULL_TREE;
+ val.mask = double_int_minus_one;
+ }
+ return val;
+}
+
/* Evaluate statement STMT.
Valid only for assignments, calls, conditionals, and switches. */
@@ -1714,6 +1790,23 @@ evaluate_stmt (gimple stmt)
default:;
}
}
+ if (is_gimple_call (stmt) && gimple_call_lhs (stmt))
+ {
+ tree fntype = gimple_call_fntype (stmt);
+ if (fntype)
+ {
+ tree attrs = lookup_attribute ("assume_aligned",
+ TYPE_ATTRIBUTES (fntype));
+ if (attrs)
+ val = bit_value_alloc_assume_aligned_attribute (stmt, attrs,
+ val, false);
+ attrs = lookup_attribute ("alloc_align",
+ TYPE_ATTRIBUTES (fntype));
+ if (attrs)
+ val = bit_value_alloc_assume_aligned_attribute (stmt, attrs,
+ val, true);
+ }
+ }
is_constant = (val.lattice_val == CONSTANT);
}
--- gcc/doc/extend.texi.jj 2014-02-04 01:35:58.000000000 +0100
+++ gcc/doc/extend.texi 2014-02-06 15:20:28.728138862 +0100
@@ -2154,8 +2154,8 @@ The keyword @code{__attribute__} allows
attributes when making a declaration. This keyword is followed by an
attribute specification inside double parentheses. The following
attributes are currently defined for functions on all targets:
-@code{aligned}, @code{alloc_size}, @code{noreturn},
-@code{returns_twice}, @code{noinline}, @code{noclone},
+@code{aligned}, @code{alloc_size}, @code{alloc_align}, @code{assume_aligned},
+@code{noreturn}, @code{returns_twice}, @code{noinline}, @code{noclone},
@code{always_inline}, @code{flatten}, @code{pure}, @code{const},
@code{nothrow}, @code{sentinel}, @code{format}, @code{format_arg},
@code{no_instrument_function}, @code{no_split_stack},
@@ -2249,6 +2249,46 @@ declares that @code{my_calloc} returns m
the product of parameter 1 and 2 and that @code{my_realloc} returns memory
of the size given by parameter 2.
+@item alloc_align
+@cindex @code{alloc_align} attribute
+The @code{alloc_align} attribute is used to tell the compiler that the
+function return value points to memory, where the returned pointer minimum
+alignment is given by one of the functions parameters. GCC uses this
+information to improve pointer alignment analysis.
+
+The function parameter denoting the allocated alignment is specified by
+one integer argument, whose number is the argument of the attribute.
+Argument numbering starts at one.
+
+For instance,
+
+@smallexample
+void* my_memalign(size_t, size_t) __attribute__((alloc_align(1)))
+@end smallexample
+
+@noindent
+declares that @code{my_memalign} returns memory with minimum alignment
+given by parameter 1.
+
+@item assume_aligned
+@cindex @code{assume_aligned} attribute
+The @code{assume_aligned} attribute is used to tell the compiler that the
+function return value points to memory, where the returned pointer minimum
+alignment is given by the first argument.
+If the attribute has two arguments, the second argument is misalignment offset.
+
+For instance
+
+@smallexample
+void* my_alloc1(size_t) __attribute__((assume_aligned(16)))
+void* my_alloc2(size_t) __attribute__((assume_aligned(32, 8)))
+@end smallexample
+
+@noindent
+declares that @code{my_alloc1} returns 16-byte aligned pointer and
+that @code{my_alloc2} returns a pointer whose value modulo 32 is equal
+to 8.
+
@item always_inline
@cindex @code{always_inline} function attribute
Generally, functions are not inlined unless optimization is specified.
--- gcc/testsuite/gcc.dg/attr-alloc_align-1.c.jj 2014-02-06
15:41:05.866432468 +0100
+++ gcc/testsuite/gcc.dg/attr-alloc_align-1.c 2014-02-06 15:58:20.427853133
+0100
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+double *my_alloc1 (int len, int align) __attribute__((__alloc_align__ (2)));
+double *my_alloc2 (int align, int len) __attribute__((alloc_align (1)));
+
+void
+test1 (int len, int align)
+{
+ int i;
+ double *__restrict o1 = my_alloc1 (len, 32);
+ double *__restrict o2 = my_alloc1 (len, 32);
+ double *__restrict o3 = my_alloc1 (len, 32);
+ double *__restrict i1 = my_alloc1 (len, 32);
+ double *__restrict i2 = my_alloc1 (len, align);
+ for (i = 0; i < len; ++i)
+ {
+ o1[i] = i1[i] * i2[i];
+ o2[i] = i1[i] + i2[i];
+ o3[i] = i1[i] - i2[i];
+ }
+}
+
+void
+test2 (int len, int align)
+{
+ int i;
+ double *__restrict o1 = my_alloc2 (32, len);
+ double *__restrict o2 = my_alloc2 (32, len);
+ double *__restrict o3 = my_alloc2 (32, len);
+ double *__restrict i1 = my_alloc2 (32, len);
+ double *__restrict i2 = my_alloc2 (align, len);
+ for (i = 0; i < len; ++i)
+ {
+ o1[i] = i1[i] * i2[i];
+ o2[i] = i1[i] + i2[i];
+ o3[i] = i1[i] - i2[i];
+ }
+}
--- gcc/testsuite/gcc.dg/attr-alloc_align-2.c.jj 2014-02-06
15:38:34.369258030 +0100
+++ gcc/testsuite/gcc.dg/attr-alloc_align-2.c 2014-02-06 16:28:27.202071608
+0100
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+
+int i;
+void *f1 (int) __attribute__((alloc_align (1)));
+void *f2 (int, int, int) __attribute__((alloc_align (3)));
+void *f3 (void) __attribute__((alloc_align)); /* { dg-error "wrong number of
arguments specified" } */
+void *f4 (int, int) __attribute__((alloc_align (1, 2))); /* { dg-error "wrong
number of arguments specified" } */
+void *f5 (void) __attribute__((alloc_align (i))); /* { dg-warning "outside
range" } */
+void *f6 (int) __attribute__((alloc_align (0))); /* { dg-warning "outside
range" } */
+void *f7 (int) __attribute__((alloc_align (2))); /* { dg-warning "outside
range" } */
--- gcc/testsuite/gcc.dg/attr-alloc_align-3.c.jj 2014-02-06
16:20:23.550709898 +0100
+++ gcc/testsuite/gcc.dg/attr-alloc_align-3.c 2014-02-06 16:24:05.497509170
+0100
@@ -0,0 +1,56 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+char *my_alloc1 (int len, int align) __attribute__((__alloc_align__ (2)));
+char *my_alloc2 (int align, int len) __attribute__((alloc_align (1)));
+
+int
+test1 (int len)
+{
+ int i;
+ char *p = my_alloc1 (len, 32);
+ return ((__INTPTR_TYPE__) p) & 31;
+}
+
+int
+test2 (int len)
+{
+ int i;
+ char *p = my_alloc2 (32, len);
+ return ((__INTPTR_TYPE__) p) & 31;
+}
+
+int
+test3 (int len)
+{
+ int i;
+ char *p = my_alloc1 (len, 16);
+ return ((__INTPTR_TYPE__) p) & 15;
+}
+
+int
+test4 (int len)
+{
+ int i;
+ char *p = my_alloc2 (16, len);
+ return ((__INTPTR_TYPE__) p) & 15;
+}
+
+int
+test5 (int len, int align)
+{
+ int i;
+ char *p = my_alloc1 (len, align);
+ return ((__INTPTR_TYPE__) p) & 15;
+}
+
+int
+test6 (int len, int align)
+{
+ int i;
+ char *p = my_alloc2 (align, len);
+ return ((__INTPTR_TYPE__) p) & 15;
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 4 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
--- gcc/testsuite/gcc.dg/attr-assume_aligned-1.c.jj 2014-02-06
15:30:31.717867866 +0100
+++ gcc/testsuite/gcc.dg/attr-assume_aligned-1.c 2014-02-06
15:43:29.848668818 +0100
@@ -0,0 +1,39 @@
+/* { dg-do compile } */
+/* { dg-options "-O3" } */
+
+double *my_alloc1 (int len) __attribute__((__assume_aligned__ (16)));
+double *my_alloc2 (int len) __attribute__((__assume_aligned__ (32, 16)));
+
+void
+test1 (int len)
+{
+ int i;
+ double *__restrict o1 = my_alloc1 (len);
+ double *__restrict o2 = my_alloc1 (len);
+ double *__restrict o3 = my_alloc1 (len);
+ double *__restrict i1 = my_alloc1 (len);
+ double *__restrict i2 = my_alloc1 (len);
+ for (i = 0; i < len; ++i)
+ {
+ o1[i] = i1[i] * i2[i];
+ o2[i] = i1[i] + i2[i];
+ o3[i] = i1[i] - i2[i];
+ }
+}
+
+void
+test2 (int len)
+{
+ int i;
+ double *__restrict o1 = my_alloc2 (len);
+ double *__restrict o2 = my_alloc2 (len);
+ double *__restrict o3 = my_alloc2 (len);
+ double *__restrict i1 = my_alloc2 (len);
+ double *__restrict i2 = my_alloc2 (len);
+ for (i = 0; i < len; ++i)
+ {
+ o1[i] = i1[i] * i2[i];
+ o2[i] = i1[i] + i2[i];
+ o3[i] = i1[i] - i2[i];
+ }
+}
--- gcc/testsuite/gcc.dg/attr-assume_aligned-2.c.jj 2014-02-06
15:30:36.340844433 +0100
+++ gcc/testsuite/gcc.dg/attr-assume_aligned-2.c 2014-02-06
16:28:56.985935446 +0100
@@ -0,0 +1,8 @@
+/* { dg-do compile } */
+
+int i;
+void *f1 (void) __attribute__((assume_aligned (32)));
+void *f2 (void) __attribute__((assume_aligned (16, 4)));
+void *f3 (void) __attribute__((assume_aligned)); /* { dg-error "wrong number
of arguments specified" } */
+void *f4 (void) __attribute__((assume_aligned (32, 16, 8))); /* { dg-error
"wrong number of arguments specified" } */
+void *f5 (void) __attribute__((assume_aligned (i))); /* { dg-warning "integer
constant" } */
--- gcc/testsuite/gcc.dg/attr-assume_aligned-3.c.jj 2014-02-06
16:24:56.038240610 +0100
+++ gcc/testsuite/gcc.dg/attr-assume_aligned-3.c 2014-02-06
16:26:34.432711183 +0100
@@ -0,0 +1,24 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-optimized" } */
+
+char *my_alloc1 (int len) __attribute__((__assume_aligned__ (32)));
+char *my_alloc2 (int len) __attribute__((assume_aligned (32, 4)));
+
+int
+test1 (int len)
+{
+ int i;
+ char *p = my_alloc1 (len);
+ return ((__INTPTR_TYPE__) p) & 31;
+}
+
+int
+test2 (int len)
+{
+ int i;
+ char *p = my_alloc2 (len);
+ return (((__INTPTR_TYPE__) p) & 31) != 4;
+}
+
+/* { dg-final { scan-tree-dump-times "return 0" 2 "optimized" } } */
+/* { dg-final { cleanup-tree-dump "optimized" } } */
Jakub
