The cast from void* to T* in std::assume_aligned is not valid in a
constexpr function. The optimization hint is redundant during constant
evaluation anyway (the compiler can see the object and knows its
alignment). Simply return the original pointer without applying the
__builtin_assume_aligned hint to it when doing constant evaluation.
This change also removes the preprocessor branch that works around
uintptr_t not being available. We already assume that type is present
elsewhere in the library.
libstdc++-v3/ChangeLog:
PR libstdc++/97132
* include/bits/align.h (align) [!_GLIBCXX_USE_C99_STDINT_TR1]:
Remove unused code.
(assume_aligned): Do not use __builtin_assume_aligned during
constant evaluation.
* testsuite/20_util/assume_aligned/1.cc: Improve test.
* testsuite/20_util/assume_aligned/97132.cc: New test.
This makes sure to emit full declaration DIEs including
formal parameters for used external functions. This helps
debugging when debug information of the external entity is
not available and also helps external tools cross-checking
ABI compatibility which was the bug reporters use case.
For cc1 this affects debug information size as follows:
VM SIZE FILE SIZE
++++++++++++++ GROWING ++++++++++++++
[ = ] 0 .debug_info +1.63Mi +1.3%
[ = ] 0 .debug_str +263Ki +3.4%
[ = ] 0 .debug_abbrev +101Ki +4.9%
[ = ] 0 .debug_line +5.71Ki +0.0%
+44% +16 [Unmapped] +48 +1.2%
-------------- SHRINKING --------------
[ = ] 0 .debug_loc -213 -0.0%
-0.0% -48 .text -48 -0.0%
[ = ] 0 .debug_ranges -16 -0.0%
-0.0% -32 TOTAL +1.99Mi +0.6%
and DWARF compression via DWZ can only shave off minor bits
here.
Previously we emitted no DIEs for external functions at all
unless they were referenced via DW_TAG_GNU_call_site which
for some GCC revs caused a regular DIE to appear and since
GCC 4.9 only a stub without formal parameters. This means
at -O0 we did not emit any DIE for external functions
but with optimization we emitted stubs.
2020-07-30 Richard Biener <rguenther@suse.de>
PR debug/96383
* langhooks-def.h (lhd_finalize_early_debug): Declare.
(LANG_HOOKS_FINALIZE_EARLY_DEBUG): Define.
(LANG_HOOKS_INITIALIZER): Amend.
* langhooks.c: Include cgraph.h and debug.h.
(lhd_finalize_early_debug): Default implementation from
former code in finalize_compilation_unit.
* langhooks.h (lang_hooks::finalize_early_debug): Add.
* cgraphunit.c (symbol_table::finalize_compilation_unit):
Call the finalize_early_debug langhook.
gcc/c-family/
* c-common.h (c_common_finalize_early_debug): Declare.
* c-common.c: Include debug.h.
(c_common_finalize_early_debug): finalize_early_debug langhook
implementation generating debug for extern declarations.
gcc/c/
* c-objc-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG):
Define to c_common_finalize_early_debug.
gcc/cp/
* cp-objcp-common.h (LANG_HOOKS_FINALIZE_EARLY_DEBUG):
Define to c_common_finalize_early_debug.
gcc/testsuite/
* gcc.dg/debug/dwarf2/pr96383-1.c: New testcase.
* gcc.dg/debug/dwarf2/pr96383-2.c: Likewise.
libstdc++-v3/
* testsuite/20_util/assume_aligned/3.cc: Use -g0.
