[lldb] Use local definition of get_cpuid_count

[JosephTremoulet]

Summary

This is needed for gcc/cstdlib++ 5.4.0, where __get_cpuid_count is not
defined in cpuid.h.

[JosephTremoulet]

@labath, as discussed in D59991, I went with a local copy of the function since I didn't see an obvious opportunity to tweak the calling code, but maybe I overlooked something. My copy of cpuid.h matches https://github.com/gcc-mirror/gcc/blob/gcc-5-branch/gcc/config/i386/cpuid.h

[labath]

The chosen approach looks fine to me. The only nit I have is that llvm style prefers static functions over ones in anonymous namespaces (though this file is not very consistent in that aspect already).

Do you have commit access or shall I commit this for you?

[JosephTremoulet]

• Use static function rather than anonymous namespace

[JosephTremoulet]

Switched to static function, and yes I do have commit access. Thanks for the review!

lldb/source/Plugins/Process/Linux/NativeRegisterContextLinux_x86_64.cpp

 #include <linux/elf.h>
 
 using namespace lldb_private;
 using namespace lldb_private::process_linux;
 
 // Private namespace.
 
 namespace {
+// Newer toolchains define __get_cpuid_count in cpuid.h, but some
+// older-but-still-supported ones (e.g. gcc 5.4.0) don't, so we
+// define it locally here, following the definition in clang/lib/Headers.
+inline int get_cpuid_count (unsigned int __leaf,
+                            unsigned int __subleaf,
+                            unsigned int *__eax, unsigned int *__ebx,
+                            unsigned int *__ecx, unsigned int *__edx)
+{
+    unsigned int __max_leaf = __get_cpuid_max(__leaf & 0x80000000, 0);
+
+    if (__max_leaf == 0 || __max_leaf < __leaf)
+        return 0;
+
+    __cpuid_count(__leaf, __subleaf, *__eax, *__ebx, *__ecx, *__edx);
+    return 1;
+}
+
 // x86 32-bit general purpose registers.
 const uint32_t g_gpr_regnums_i386[] = {
     lldb_eax_i386,      lldb_ebx_i386,    lldb_ecx_i386, lldb_edx_i386,
     lldb_edi_i386,      lldb_esi_i386,    lldb_ebp_i386, lldb_esp_i386,
     lldb_eip_i386,      lldb_eflags_i386, lldb_cs_i386,  lldb_fs_i386,
     lldb_gs_i386,       lldb_ss_i386,     lldb_ds_i386,  lldb_es_i386,
     lldb_ax_i386,       lldb_bx_i386,     lldb_cx_i386,  lldb_dx_i386,
     lldb_di_i386,       lldb_si_i386,     lldb_bp_i386,  lldb_sp_i386,

 // sizeof(FPR) so that the allocated buffer can be safely cast to FPR*.
 static std::size_t GetXSTATESize() {
   unsigned int eax, ebx, ecx, edx;
   // First check whether the XSTATE are is supported at all.
   if (!__get_cpuid(1, &eax, &ebx, &ecx, &edx) || !(ecx & bit_XSAVE))
     return sizeof(FPR);
 
   // Then fetch the maximum size of the area.
-  if (!__get_cpuid_count(0x0d, 0, &eax, &ebx, &ecx, &edx))
+  if (!get_cpuid_count(0x0d, 0, &eax, &ebx, &ecx, &edx))
     return sizeof(FPR);
   return std::max<std::size_t>(ecx, sizeof(FPR));
 }
 
 NativeRegisterContextLinux_x86_64::NativeRegisterContextLinux_x86_64(
     const ArchSpec &target_arch, NativeThreadProtocol &native_thread)
     : NativeRegisterContextLinux(native_thread,
                                  CreateRegisterInfoInterface(target_arch)),