From
http://embed.cs.utah.edu/embarrassing/dec_09/harvest/gcc-head_llvm-gcc-head/
typedef unsigned char u8;
typedef unsigned int u32;
#pragma pack(1)
#pragma pack()
#pragma pack(1)
#pragma pack()
#pragma pack(1)
#pragma pack()
#pragma pack(4)
#pragma pack()
union __anonunion_out_195
{
u32 value;
u8 bytes[4];
};
union __anonunion_in_196
{
u32 value;
u8 bytes[4];
};
extern void acpi_ut_track_stack_ptr (void);
u32 acpi_ut_dword_byte_swap (u32 value);
u32
acpi_ut_dword_byte_swap (u32 value)
{
union __anonunion_out_195 out;
union __anonunion_in_196 in;
{
acpi_ut_track_stack_ptr ();
in.value = value;
out.bytes[0] = in.bytes[3];
out.bytes[1] = in.bytes[2];
out.bytes[2] = in.bytes[1];
out.bytes[3] = in.bytes[0];
return (out.value);
}
}
/* Checksum = 1251E213 */
does not turn into bswap, while llvm does that.
There's bswap detection code in tree-ssa-math-ops.c, but it doesn't
seem to work for this union pattern. Perhaps it should?
--
Summary: bswap not recognized for union
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: enhancement
Priority: P3
Component: tree-optimization
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: andi-gcc at firstfloor dot org
GCC host triplet: x86_64-linux
GCC target triplet: x86_64-linux
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42587
