Various pthread types on hppa-linux require an alignment of 16 bytes for ABI
reasons. This is larger
than the current implementations of max_align_t and max_align_t_align. As a
result, the patch to
implement C++17 over-aligned new causes warnings on hppa. The thread here
discusses the problem:
https://gcc.gnu.org/ml/gcc-patches/2016-09/msg01593.html
The attached patch implements a new hook to allow overriding the default
implementation of max_align_t_align
in the PA backend. It changes the max_align_t alignment to 16 bytes on 32-bit
hppa-linux. I added an additional
comment to BIGGEST_ALIGNMENT in pa.h to document the alignment choices for long
double on hpux. I also
defined MALLOC_ABI_ALIGNMENT so that it reflects the behaviour of the glibc and
hpux malloc implementations.
Tested on hppa2.0w-hp-hpux11.11, hppa64-hp-hpux11.11 and hppa-unknown-linux-gnu
with no observed
regressions.
Okay for trunk?
Dave
--
John David Anglin dave.ang...@bell.net
2016-10-08 John David Anglin <dang...@gcc.gnu.org>
gcc/c-family/
* c-common.c (max_align_t_align): Move to targhooks.c.
* c-common.h (max_align_t_align): Delete.
gcc/
* target.def (max_align_t_align): New target hook.
* targhooks.c (default_max_align_t_align): New.
* targhooks.h (default_max_align_t_align): Declare.
* config/pa/pa.h (BIGGEST_ALIGNMENT): Adjust comment.
(MALLOC_ABI_ALIGNMENT): Define.
* config/pa/pa.c (pa_max_align_t_align): New.
(TARGET_MAX_ALIGN_T_ALIGN): Define.
* doc/tm.texi.in (TARGET_MAX_ALIGN_T_ALIGN): Add documentation hook.
* doc/tm.texi: Update.
gcc/cp/
* decl.c (cxx_init_decl_processing): Use max_align_t_align target hook.
* init.c (build_new_1): Likewise.
Index: c-family/c-common.c
===================================================================
--- c-family/c-common.c (revision 240688)
+++ c-family/c-common.c (working copy)
@@ -12899,22 +12899,6 @@
return stv_nothing;
}
-/* Return the alignment of std::max_align_t.
-
- [support.types.layout] The type max_align_t is a POD type whose alignment
- requirement is at least as great as that of every scalar type, and whose
- alignment requirement is supported in every context. */
-
-unsigned
-max_align_t_align ()
-{
- unsigned int max_align = MAX (TYPE_ALIGN (long_long_integer_type_node),
- TYPE_ALIGN (long_double_type_node));
- if (float128_type_node != NULL_TREE)
- max_align = MAX (max_align, TYPE_ALIGN (float128_type_node));
- return max_align;
-}
-
/* Return true iff ALIGN is an integral constant that is a fundamental
alignment, as defined by [basic.align] in the c++-11
specifications.
@@ -12928,7 +12912,7 @@
bool
cxx_fundamental_alignment_p (unsigned align)
{
- return (align <= max_align_t_align ());
+ return (align <= targetm.max_align_t_align ());
}
/* Return true if T is a pointer to a zero-sized aggregate. */
Index: c-family/c-common.h
===================================================================
--- c-family/c-common.h (revision 240688)
+++ c-family/c-common.h (working copy)
@@ -864,7 +864,6 @@
extern bool keyword_is_storage_class_specifier (enum rid);
extern bool keyword_is_type_qualifier (enum rid);
extern bool keyword_is_decl_specifier (enum rid);
-extern unsigned max_align_t_align (void);
extern bool cxx_fundamental_alignment_p (unsigned);
extern bool pointer_to_zero_sized_aggr_p (tree);
extern bool diagnose_mismatched_attributes (tree, tree);
Index: config/pa/pa.c
===================================================================
--- config/pa/pa.c (revision 240688)
+++ config/pa/pa.c (working copy)
@@ -194,6 +194,7 @@
static bool pa_legitimate_constant_p (machine_mode, rtx);
static unsigned int pa_section_type_flags (tree, const char *, int);
static bool pa_legitimate_address_p (machine_mode, rtx, bool);
+static unsigned int pa_max_align_t_align (void);
/* The following extra sections are only used for SOM. */
static GTY(()) section *som_readonly_data_section;
@@ -400,6 +401,9 @@
#undef TARGET_LRA_P
#define TARGET_LRA_P hook_bool_void_false
+#undef TARGET_MAX_ALIGN_T_ALIGN
+#define TARGET_MAX_ALIGN_T_ALIGN pa_max_align_t_align
+
struct gcc_target targetm = TARGET_INITIALIZER;
/* Parse the -mfixed-range= option string. */
@@ -10719,4 +10723,16 @@
return NULL_RTX;
}
+/* The maximimum alignment in bits for the POD type std:max_align_t.
+ This is set to 128 on 32-bit non HP-UX systems to suppress warnings
+ about new with extended alignment. This arises because various POSIX
+ types such as pthread_mutex_t have for historical reasons 128-bit
+ alignment but the default alignment of std:max_align_t is 64 bits. */
+
+static unsigned int
+pa_max_align_t_align (void)
+{
+ return TARGET_HPUX && !TARGET_64BIT ? 64 : 128;
+}
+
#include "gt-pa.h"
Index: config/pa/pa.h
===================================================================
--- config/pa/pa.h (revision 240688)
+++ config/pa/pa.h (working copy)
@@ -292,9 +292,21 @@
/* A bit-field declared as `int' forces `int' alignment for the struct. */
#define PCC_BITFIELD_TYPE_MATTERS 1
-/* No data type wants to be aligned rounder than this. */
+/* No data type wants to be aligned rounder than this. The long double
+ type has 16-byte alignment on the 64-bit target even though it was never
+ implemented in hardware. The software implementation only needs 8-byte
+ alignment. This is to match the HP compilers. */
#define BIGGEST_ALIGNMENT (2 * BITS_PER_WORD)
+/* Alignment, in bits, a C conformant malloc implementation has to provide.
+ The HP-UX malloc implementation provides a default alignment of 8 bytes.
+ This can be increased with mallopt. The glibc implementation also provides
+ 8-byte alignment. Note that this isn't enough for various POSIX types such
+ as pthread_mutex_t. However, since we no longer need the 16-byte alignment
+ for atomic operations, we ignore the nominal alignment specified for these
+ types. The same is true for long double on 64-bit HP-UX. */
+#define MALLOC_ABI_ALIGNMENT (64)
+
/* Get around hp-ux assembler bug, and make strcpy of constants fast. */
#define CONSTANT_ALIGNMENT(EXP, ALIGN) \
(TREE_CODE (EXP) == STRING_CST \
Index: cp/decl.c
===================================================================
--- cp/decl.c (revision 240688)
+++ cp/decl.c (working copy)
@@ -4141,7 +4141,7 @@
if (aligned_new_threshold == -1)
aligned_new_threshold = (cxx_dialect >= cxx1z) ? 1 : 0;
if (aligned_new_threshold == 1)
- aligned_new_threshold = max_align_t_align () / BITS_PER_UNIT;
+ aligned_new_threshold = targetm.max_align_t_align () / BITS_PER_UNIT;
{
tree newattrs, extvisattr;
Index: cp/init.c
===================================================================
--- cp/init.c (revision 240688)
+++ cp/init.c (working copy)
@@ -3017,7 +3017,7 @@
gcc_assert (alloc_fn != NULL_TREE);
if (warn_aligned_new
- && TYPE_ALIGN (elt_type) > max_align_t_align ()
+ && TYPE_ALIGN (elt_type) > targetm.max_align_t_align ()
&& (warn_aligned_new > 1
|| CP_DECL_CONTEXT (alloc_fn) == global_namespace)
&& !aligned_allocation_fn_p (alloc_fn))
Index: doc/tm.texi
===================================================================
--- doc/tm.texi (revision 240688)
+++ doc/tm.texi (working copy)
@@ -11686,6 +11686,10 @@
ISO C11 requires atomic compound assignments that may raise floating-point
exceptions to raise exceptions corresponding to the arithmetic operation whose
result was successfully stored in a compare-and-exchange sequence. This
requires code equivalent to calls to @code{feholdexcept}, @code{feclearexcept}
and @code{feupdateenv} to be generated at appropriate points in the
compare-and-exchange sequence. This hook should set @code{*@var{hold}} to an
expression equivalent to the call to @code{feholdexcept}, @code{*@var{clear}}
to an expression equivalent to the call to @code{feclearexcept} and
@code{*@var{update}} to an expression equivalent to the call to
@code{feupdateenv}. The three expressions are @code{NULL_TREE} on entry to the
hook and may be left as @code{NULL_TREE} if no code is required in a particular
place. The default implementation leaves all three expressions as
@code{NULL_TREE}. The @code{__atomic_feraiseexcept} function from
@code{libatomic} may be of use as part of the code generated in
@code{*@var{update}}.
@end deftypefn
+@deftypefn {Target Hook} {unsigned int} TARGET_MAX_ALIGN_T_ALIGN (void)
+If defined, this function returns the alignment in bits for std:max_align_t.
The default is suitable for most targets.
+@end deftypefn
+
@deftypefn {Target Hook} void TARGET_RECORD_OFFLOAD_SYMBOL (tree)
Used when offloaded functions are seen in the compilation unit and no named
sections are available. It is called once for each symbol that must be
Index: doc/tm.texi.in
===================================================================
--- doc/tm.texi.in (revision 240688)
+++ doc/tm.texi.in (working copy)
@@ -8224,6 +8224,8 @@
@hook TARGET_ATOMIC_ASSIGN_EXPAND_FENV
+@hook TARGET_MAX_ALIGN_T_ALIGN
+
@hook TARGET_RECORD_OFFLOAD_SYMBOL
@hook TARGET_OFFLOAD_OPTIONS
Index: target.def
===================================================================
--- target.def (revision 240688)
+++ target.def (working copy)
@@ -5894,6 +5894,15 @@
void, (tree *hold, tree *clear, tree *update),
default_atomic_assign_expand_fenv)
+/* Return an unsigned int representing the alignment (in bits) of
+ std:max_align_t. This allows the default alignment to be overridden. */
+DEFHOOK
+(max_align_t_align,
+"If defined, this function returns the alignment in bits for std:max_align_t.\
+ The default is suitable for most targets. ",
+ unsigned int, (void),
+ default_max_align_t_align)
+
/* Leave the boolean fields at the end. */
/* True if we can create zeroed data by switching to a BSS section
Index: targhooks.c
===================================================================
--- targhooks.c (revision 240688)
+++ targhooks.c (working copy)
@@ -1907,6 +1907,23 @@
{
}
+/* Default implementation of TARGET_MAX_ALIGN_T_ALIGN to return alignment
+ in bits of std::max_align_t.
+
+ [support.types.layout] The type max_align_t is a POD type whose alignment
+ requirement is at least as great as that of every scalar type, and whose
+ alignment requirement is supported in every context. */
+
+unsigned int
+default_max_align_t_align (void)
+{
+ unsigned int max_align = MAX (TYPE_ALIGN (long_long_integer_type_node),
+ TYPE_ALIGN (long_double_type_node));
+ if (float128_type_node != NULL_TREE)
+ max_align = MAX (max_align, TYPE_ALIGN (float128_type_node));
+ return max_align;
+}
+
#ifndef PAD_VARARGS_DOWN
#define PAD_VARARGS_DOWN BYTES_BIG_ENDIAN
#endif
Index: targhooks.h
===================================================================
--- targhooks.h (revision 240688)
+++ targhooks.h (working copy)
@@ -262,5 +262,6 @@
optimization_type);
extern unsigned int default_max_noce_ifcvt_seq_cost (edge);
+extern unsigned int default_max_align_t_align (void);
#endif /* GCC_TARGHOOKS_H */
