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From: Florian Weimer <fw@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org Subject: [gcc r13-4954] Define __LIBGCC_DWARF_REG_SIZES_CONSTANT__ if DWARF register size is constant Date: Mon, 2 Jan 2023 15:18:15 +0000 (GMT) [thread overview] Message-ID: <20230102151815.DE474385842C@sourceware.org> (raw) https://gcc.gnu.org/g:97bbdb726aba76ead550e25061029cf0aa78671b commit r13-4954-g97bbdb726aba76ead550e25061029cf0aa78671b Author: Florian Weimer <fweimer@redhat.com> Date: Mon Jan 2 16:18:02 2023 +0100 Define __LIBGCC_DWARF_REG_SIZES_CONSTANT__ if DWARF register size is constant And use that to speed up the libgcc unwinder. gcc/ * debug.h (dwarf_reg_sizes_constant): Declare. * dwarf2cfi.cc (dwarf_reg_sizes_constant): New function. gcc/c-family/ * c-cppbuiltin.cc (__LIBGCC_DWARF_REG_SIZES_CONSTANT__): Define if constant is known. libgcc/ * unwind-dw2.c (dwarf_reg_size): New function. (_Unwind_GetGR, _Unwind_SetGR, _Unwind_SetGRPtr) (_Unwind_SetSpColumn, uw_install_context_1): Use it. (uw_init_context_1): Do not initialize dwarf_reg_size_table if not in use. Diff: --- gcc/c-family/c-cppbuiltin.cc | 6 ++++++ gcc/debug.h | 2 ++ gcc/dwarf2cfi.cc | 23 +++++++++++++++++++++++ libgcc/unwind-dw2.c | 41 +++++++++++++++++++++++++++++------------ 4 files changed, 60 insertions(+), 12 deletions(-) diff --git a/gcc/c-family/c-cppbuiltin.cc b/gcc/c-family/c-cppbuiltin.cc index 333f3e138d6..011478c88da 100644 --- a/gcc/c-family/c-cppbuiltin.cc +++ b/gcc/c-family/c-cppbuiltin.cc @@ -1521,6 +1521,12 @@ c_cpp_builtins (cpp_reader *pfile) #endif builtin_define_with_int_value ("__LIBGCC_DWARF_FRAME_REGISTERS__", DWARF_FRAME_REGISTERS); + { + int value = dwarf_reg_sizes_constant (); + if (value > 0) + builtin_define_with_int_value ("__LIBGCC_DWARF_REG_SIZES_CONSTANT__", + value); + } #ifdef EH_RETURN_STACKADJ_RTX cpp_define (pfile, "__LIBGCC_EH_RETURN_STACKADJ_RTX__"); #endif diff --git a/gcc/debug.h b/gcc/debug.h index 799d5e316a2..4fe9f3570ac 100644 --- a/gcc/debug.h +++ b/gcc/debug.h @@ -245,6 +245,8 @@ extern const struct gcc_debug_hooks vmsdbg_debug_hooks; /* Dwarf2 frame information. */ +extern int dwarf_reg_sizes_constant (); + extern void dwarf2out_begin_prologue (unsigned int, unsigned int, const char *); extern void dwarf2out_vms_end_prologue (unsigned int, const char *); diff --git a/gcc/dwarf2cfi.cc b/gcc/dwarf2cfi.cc index 4d2bd869a4b..d5a27dc36c5 100644 --- a/gcc/dwarf2cfi.cc +++ b/gcc/dwarf2cfi.cc @@ -334,6 +334,29 @@ generate_dwarf_reg_sizes (poly_uint16 *sizes) targetm.init_dwarf_reg_sizes_extra (sizes); } +/* Return 0 if the DWARF register sizes are not constant, otherwise + return the size constant. */ + +int +dwarf_reg_sizes_constant () +{ + poly_uint16 *sizes = XALLOCAVEC (poly_uint16, DWARF_FRAME_REGISTERS); + generate_dwarf_reg_sizes (sizes); + + int result; + for (unsigned int i = 0; i < DWARF_FRAME_REGISTERS; i++) + { + unsigned short value; + if (!sizes[i].is_constant (&value)) + return 0; + if (i == 0) + result = value; + else if (result != value) + return 0; + } + return result; +} + /* Generate code to initialize the dwarf register size table located at the provided ADDRESS. */ diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c index eaceace2029..c370121bb29 100644 --- a/libgcc/unwind-dw2.c +++ b/libgcc/unwind-dw2.c @@ -148,9 +148,25 @@ struct _Unwind_Context char by_value[__LIBGCC_DWARF_FRAME_REGISTERS__+1]; }; +#ifdef __LIBGCC_DWARF_REG_SIZES_CONSTANT__ +static inline unsigned char +dwarf_reg_size (int index __attribute__ ((__unused__))) +{ + return __LIBGCC_DWARF_REG_SIZES_CONSTANT__; +} +#else /* Byte size of every register managed by these routines. */ static unsigned char dwarf_reg_size_table[__LIBGCC_DWARF_FRAME_REGISTERS__+1]; + +static inline unsigned char +dwarf_reg_size (unsigned index) +{ + gcc_assert (index < sizeof (dwarf_reg_size_table)); + return dwarf_reg_size_table[index]; +} +#endif + \f /* Read unaligned data from the instruction buffer. */ @@ -232,8 +248,7 @@ _Unwind_GetGR (struct _Unwind_Context *context, int regno) #endif index = DWARF_REG_TO_UNWIND_COLUMN (regno); - gcc_assert (index < (int) sizeof(dwarf_reg_size_table)); - size = dwarf_reg_size_table[index]; + size = dwarf_reg_size (index); val = context->reg[index]; if (_Unwind_IsExtendedContext (context) && context->by_value[index]) @@ -280,8 +295,7 @@ _Unwind_SetGR (struct _Unwind_Context *context, int index, _Unwind_Word val) void *ptr; index = DWARF_REG_TO_UNWIND_COLUMN (index); - gcc_assert (index < (int) sizeof(dwarf_reg_size_table)); - size = dwarf_reg_size_table[index]; + size = dwarf_reg_size (index); if (_Unwind_IsExtendedContext (context) && context->by_value[index]) { @@ -329,9 +343,8 @@ _Unwind_SetGRValue (struct _Unwind_Context *context, int index, _Unwind_Word val) { index = DWARF_REG_TO_UNWIND_COLUMN (index); - gcc_assert (index < (int) sizeof(dwarf_reg_size_table)); /* Return column size may be smaller than _Unwind_Context_Reg_Val. */ - gcc_assert (dwarf_reg_size_table[index] <= sizeof (_Unwind_Context_Reg_Val)); + gcc_assert (dwarf_reg_size (index) <= sizeof (_Unwind_Context_Reg_Val)); context->by_value[index] = 1; context->reg[index] = _Unwind_Get_Unwind_Context_Reg_Val (val); @@ -1387,7 +1400,7 @@ static inline void _Unwind_SetSpColumn (struct _Unwind_Context *context, void *cfa, _Unwind_SpTmp *tmp_sp) { - int size = dwarf_reg_size_table[__builtin_dwarf_sp_column ()]; + int size = dwarf_reg_size (__builtin_dwarf_sp_column ()); if (size == sizeof(_Unwind_Ptr)) tmp_sp->ptr = (_Unwind_Ptr) cfa; @@ -1573,11 +1586,13 @@ uw_advance_context (struct _Unwind_Context *context, _Unwind_FrameState *fs) } \ while (0) +#ifndef __LIBGCC_DWARF_REG_SIZES_CONSTANT__ static inline void init_dwarf_reg_size_table (void) { __builtin_init_dwarf_reg_size_table (dwarf_reg_size_table); } +#endif static void __attribute__((noinline)) uw_init_context_1 (struct _Unwind_Context *context, @@ -1596,16 +1611,18 @@ uw_init_context_1 (struct _Unwind_Context *context, code = uw_frame_state_for (context, &fs); gcc_assert (code == _URC_NO_REASON); -#if __GTHREADS +#ifndef __LIBGCC_DWARF_REG_SIZES_CONSTANT__ +# if __GTHREADS { static __gthread_once_t once_regsizes = __GTHREAD_ONCE_INIT; if (__gthread_once (&once_regsizes, init_dwarf_reg_size_table) != 0 && dwarf_reg_size_table[0] == 0) init_dwarf_reg_size_table (); } -#else +# else if (dwarf_reg_size_table[0] == 0) init_dwarf_reg_size_table (); +# endif #endif /* Force the frame state to use the known cfa value. */ @@ -1682,20 +1699,20 @@ uw_install_context_1 (struct _Unwind_Context *current, { _Unwind_Word w; _Unwind_Ptr p; - if (dwarf_reg_size_table[i] == sizeof (_Unwind_Word)) + if (dwarf_reg_size (i) == sizeof (_Unwind_Word)) { w = (_Unwind_Internal_Ptr) t; memcpy (c, &w, sizeof (_Unwind_Word)); } else { - gcc_assert (dwarf_reg_size_table[i] == sizeof (_Unwind_Ptr)); + gcc_assert (dwarf_reg_size (i) == sizeof (_Unwind_Ptr)); p = (_Unwind_Internal_Ptr) t; memcpy (c, &p, sizeof (_Unwind_Ptr)); } } else if (t && c && t != c) - memcpy (c, t, dwarf_reg_size_table[i]); + memcpy (c, t, dwarf_reg_size (i)); } /* If the current frame doesn't have a saved stack pointer, then we
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