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dwarf2asm: Use constexpr for eh_data_format_name initialization for C++14

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Similarly to the previous patch, dwarf2asm.cc had
HAVE_DESIGNATED_INITIALIZERS support, and as fallback a huge switch.
The switch from what I can see is expanded as a jump table with 256
label pointers and code at those labels then loads addresses of
string literals.
The following patch instead uses a table with 256 const char * pointers,
NULL for ICE, non-NULL for returning something, similarly to the
HAVE_DESIGNATED_INITIALIZERS case.

2024-09-19  Jakub Jelinek  <jakub@redhat.com>

	* dwarf2asm.cc (eh_data_format_name): Use constexpr initialization
	of format_names table for C++14 instead of a large switch.
This commit is contained in:
Jakub Jelinek 2024-09-19 17:53:27 +02:00 committed by Jakub Jelinek
parent cee868ae0d
commit 16dda95e39
1 changed files with 17 additions and 2 deletions
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19
gcc/dwarf2asm.cc
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@ -488,14 +488,22 @@ eh_data_format_name (int format)
{
#if HAVE_DESIGNATED_INITIALIZERS
#define S(p, v) [p] = v,
#elif __cpp_constexpr >= 201304L
#define S(p, v) names[p] = v;
#else
#define S(p, v) case p: return v;
#endif
#if HAVE_DESIGNATED_INITIALIZERS
__extension__ static const char * const format_names[256] = {
#elif __cpp_constexpr >= 201304L
static constexpr struct format_names_s {
const char *names[256];
constexpr format_names_s () : names {}
{
#else
switch (format) {
switch (format)
{
#endif
S(DW_EH_PE_absptr, "absolute")
@ -635,8 +643,15 @@ eh_data_format_name (int format)
gcc_assert (format >= 0 && format < 0x100 && format_names[format]);
return format_names[format];
#elif __cpp_constexpr >= 201304L
}
} format_names;
gcc_assert (format >= 0 && format < 0x100 && format_names.names[format]);
return format_names.names[format];
#else
}
}
gcc_unreachable ();
#endif
}