1 files changed, 230 insertions, 85 deletions

diff --git a/gdbserver/linux-x86-tdesc.cc b/gdbserver/linux-x86-tdesc.cc
index 9fd64d8..87cf368 100644
--- a/gdbserver/linux-x86-tdesc.cc
+++ b/gdbserver/linux-x86-tdesc.cc
@@ -28,96 +28,277 @@
 #include "x86-tdesc.h"
 #include "nat/x86-linux-tdesc.h"
 
-/* Return the right x86_linux_tdesc index for a given XCR0.  Return
-   X86_TDESC_LAST if can't find a match.  */
+/* A structure used to describe a single cpu feature that might, or might
+   not, be checked for when creating a target description for one of i386,
+   amd64, or x32.  */
 
-static enum x86_linux_tdesc
-xcr0_to_tdesc_idx (uint64_t xcr0, bool is_x32)
+struct x86_tdesc_feature {
+  /* The cpu feature mask.  This is a mask against an xcr0 value.  */
+  uint64_t feature;
+
+  /* Is this feature checked when creating an i386 target description.  */
+  bool is_i386;
+
+  /* Is this feature checked when creating an amd64 target description.  */
+  bool is_amd64;
+
+  /* Is this feature checked when creating an x32 target description.  */
+  bool is_x32;
+};
+
+/* A constant table that describes all of the cpu features that are
+   checked when building a target description for i386, amd64, or x32.  */
+
+static constexpr x86_tdesc_feature x86_linux_all_tdesc_features[] = {
+  /* Feature,           i386,	amd64,	x32.  */
+  { X86_XSTATE_PKRU,	true,	true, 	true },
+  { X86_XSTATE_AVX512,	true,	true, 	true },
+  { X86_XSTATE_AVX,	true,	true, 	true },
+  { X86_XSTATE_MPX,	true,	true, 	false },
+  { X86_XSTATE_SSE,	true,	false, 	false },
+  { X86_XSTATE_X87,	true,	false, 	false }
+};
+
+/* Return a compile time constant which is a mask of all the cpu features
+   that are checked for when building an i386 target description.  */
+
+static constexpr uint64_t
+x86_linux_i386_tdesc_feature_mask ()
 {
-  if (xcr0 & X86_XSTATE_PKRU)
-    {
-      if (is_x32)
-	{
-	  /* No x32 MPX and PKU, fall back to avx_avx512.  */
-	  return X86_TDESC_AVX_AVX512;
-	}
-      else
-	return X86_TDESC_AVX_MPX_AVX512_PKU;
-    }
-  else if (xcr0 & X86_XSTATE_AVX512)
-    return X86_TDESC_AVX_AVX512;
-  else if ((xcr0 & X86_XSTATE_AVX_MPX_MASK) == X86_XSTATE_AVX_MPX_MASK)
+  uint64_t mask = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_i386)
+      mask |= entry.feature;
+
+  return mask;
+}
+
+/* Return a compile time constant which is a mask of all the cpu features
+   that are checked for when building an amd64 target description.  */
+
+static constexpr uint64_t
+x86_linux_amd64_tdesc_feature_mask ()
+{
+  uint64_t mask = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_amd64)
+      mask |= entry.feature;
+
+  return mask;
+}
+
+/* Return a compile time constant which is a mask of all the cpu features
+   that are checked for when building an x32 target description.  */
+
+static constexpr uint64_t
+x86_linux_x32_tdesc_feature_mask ()
+{
+  uint64_t mask = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_x32)
+      mask |= entry.feature;
+
+  return mask;
+}
+
+/* Return a compile time constant which is a count of the number of cpu
+   features that are checked for when building an i386 target description.  */
+
+static constexpr int
+x86_linux_i386_tdesc_count ()
+{
+  uint64_t count = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_i386)
+      ++count;
+
+  gdb_assert (count > 0);
+
+  return (1 << count);
+}
+
+/* Return a compile time constant which is a count of the number of cpu
+   features that are checked for when building an amd64 target description.  */
+
+static constexpr int
+x86_linux_amd64_tdesc_count ()
+{
+  uint64_t count = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_amd64)
+      ++count;
+
+  gdb_assert (count > 0);
+
+  return (1 << count);
+}
+
+/* Return a compile time constant which is a count of the number of cpu
+   features that are checked for when building an x32 target description.  */
+
+static constexpr int
+x86_linux_x32_tdesc_count ()
+{
+  uint64_t count = 0;
+
+  for (const auto &entry : x86_linux_all_tdesc_features)
+    if (entry.is_x32)
+      ++count;
+
+  gdb_assert (count > 0);
+
+  return (1 << count);
+}
+
+#ifdef IN_PROCESS_AGENT
+
+/* See linux-x86-tdesc.h.  */
+
+int
+x86_linux_amd64_ipa_tdesc_count ()
+{
+  return x86_linux_amd64_tdesc_count ();
+}
+
+/* See linux-x86-tdesc.h.  */
+
+int
+x86_linux_x32_ipa_tdesc_count ()
+{
+  return x86_linux_x32_tdesc_count ();
+}
+
+/* See linux-x86-tdesc.h.  */
+
+int
+x86_linux_i386_ipa_tdesc_count ()
+{
+  return x86_linux_i386_tdesc_count ();
+}
+
+#endif /* IN_PROCESS_AGENT */
+
+/* Convert an xcr0 value into an integer.  The integer will be passed to
+   the in-process-agent where it will then be passed to
+   x86_linux_tdesc_idx_to_xcr0 to get back the xcr0 value.  */
+
+int
+x86_linux_xcr0_to_tdesc_idx (uint64_t xcr0)
+{
+  /* The following table shows which features are checked for when creating
+     the target descriptions (see nat/x86-linux-tdesc.c), the feature order
+     represents the bit order within the generated index number.
+
+     i386  | x87 sse mpx avx avx512 pkru
+     amd64 |         mpx avx avx512 pkru
+     i32   |             avx avx512 pkru
+
+     The features are ordered so that for each mode (i386, amd64, i32) the
+     generated index will form a continuous range.  */
+
+  int idx = 0;
+
+  for (int i = 0; i < ARRAY_SIZE (x86_linux_all_tdesc_features); ++i)
     {
-      if (is_x32) /* No MPX on x32.  */
-	return X86_TDESC_AVX;
-      else
-	return X86_TDESC_AVX_MPX;
+      if ((xcr0 & x86_linux_all_tdesc_features[i].feature) != 0)
+	idx |= (1 << i);
     }
-  else if (xcr0 & X86_XSTATE_MPX)
+
+  return idx;
+}
+
+
+#ifdef IN_PROCESS_AGENT
+
+/* Convert an index number (as returned from x86_linux_xcr0_to_tdesc_idx)
+   into an xcr0 value which can then be used to create a target
+   description.  */
+
+uint64_t
+x86_linux_tdesc_idx_to_xcr0 (int idx)
+{
+  uint64_t xcr0 = 0;
+
+  for (int i = 0; i < ARRAY_SIZE (x86_linux_all_tdesc_features); ++i)
     {
-      if (is_x32) /* No MPX on x32.  */
-	return X86_TDESC_AVX;
-      else
-	return X86_TDESC_MPX;
+      if ((idx & (1 << i)) != 0)
+	xcr0 |= x86_linux_all_tdesc_features[i].feature;
     }
-  else if (xcr0 & X86_XSTATE_AVX)
-    return X86_TDESC_AVX;
-  else if (xcr0 & X86_XSTATE_SSE)
-    return X86_TDESC_SSE;
-  else if (xcr0 & X86_XSTATE_X87)
-    return X86_TDESC_MMX;
-  else
-    return X86_TDESC_LAST;
+
+  return xcr0;
 }
 
+#endif /* IN_PROCESS_AGENT */
+
 #if defined __i386__ || !defined IN_PROCESS_AGENT
 
-static struct target_desc *i386_tdescs[X86_TDESC_LAST] = { };
+/* A cache of all possible i386 target descriptions.  */
 
-/* Return the target description according to XCR0.  */
+static struct target_desc *i386_tdescs[x86_linux_i386_tdesc_count ()] = { };
+
+/* See nat/x86-linux-tdesc.h.  */
 
 const struct target_desc *
 i386_linux_read_description (uint64_t xcr0)
 {
-  enum x86_linux_tdesc idx = xcr0_to_tdesc_idx (xcr0, false);
+  xcr0 &= x86_linux_i386_tdesc_feature_mask ();
+  int idx = x86_linux_xcr0_to_tdesc_idx (xcr0);
 
-  if (idx == X86_TDESC_LAST)
-    return NULL;
+  gdb_assert (idx >= 0 && idx < x86_linux_i386_tdesc_count ());
 
-  struct target_desc **tdesc = &i386_tdescs[idx];
+  target_desc **tdesc = &i386_tdescs[idx];
 
-  if (*tdesc == NULL)
+  if (*tdesc == nullptr)
     {
       *tdesc = i386_create_target_description (xcr0, true, false);
 
       init_target_desc (*tdesc, i386_expedite_regs);
     }
 
-  return *tdesc;;
+  return *tdesc;
 }
 #endif
 
 #ifdef __x86_64__
 
-static target_desc *amd64_tdescs[X86_TDESC_LAST] = { };
-static target_desc *x32_tdescs[X86_TDESC_LAST] = { };
+/* A cache of all possible amd64 target descriptions.  */
+
+static target_desc *amd64_tdescs[x86_linux_amd64_tdesc_count ()] = { };
+
+/* A cache of all possible x32 target descriptions.  */
+
+static target_desc *x32_tdescs[x86_linux_x32_tdesc_count ()] = { };
+
+/* See nat/x86-linux-tdesc.h.  */
 
 const struct target_desc *
 amd64_linux_read_description (uint64_t xcr0, bool is_x32)
 {
-  enum x86_linux_tdesc idx = xcr0_to_tdesc_idx (xcr0, is_x32);
+  if (is_x32)
+    xcr0 &= x86_linux_x32_tdesc_feature_mask ();
+  else
+    xcr0 &= x86_linux_amd64_tdesc_feature_mask ();
+
+  int idx = x86_linux_xcr0_to_tdesc_idx (xcr0);
 
-  if (idx == X86_TDESC_LAST)
-    return NULL;
+  if (is_x32)
+    gdb_assert (idx >= 0 && idx < x86_linux_x32_tdesc_count ());
+  else
+    gdb_assert (idx >= 0 && idx < x86_linux_amd64_tdesc_count ());
 
-  struct target_desc **tdesc = NULL;
+  target_desc **tdesc = nullptr;
 
   if (is_x32)
     tdesc = &x32_tdescs[idx];
   else
     tdesc = &amd64_tdescs[idx];
 
-  if (*tdesc == NULL)
+  if (*tdesc == nullptr)
     {
       *tdesc = amd64_create_target_description (xcr0, is_x32, true, true);
 
@@ -127,39 +308,3 @@ amd64_linux_read_description (uint64_t xcr0, bool is_x32)
 }
 
 #endif
-
-#ifndef IN_PROCESS_AGENT
-
-int
-i386_get_ipa_tdesc_idx (const struct target_desc *tdesc)
-{
-  for (int i = 0; i < X86_TDESC_LAST; i++)
-    {
-      if (tdesc == i386_tdescs[i])
-	return i;
-    }
-
-  /* If none tdesc is found, return the one with minimum features.  */
-  return X86_TDESC_MMX;
-}
-
-#if defined __x86_64__
-int
-amd64_get_ipa_tdesc_idx (const struct target_desc *tdesc)
-{
-  for (int i = 0; i < X86_TDESC_LAST; i++)
-    {
-      if (tdesc == amd64_tdescs[i])
-	return i;
-    }
-  for (int i = 0; i < X86_TDESC_LAST; i++)
-    {
-      if (tdesc == x32_tdescs[i])
-	return i;
-    }
-
-  return X86_TDESC_SSE;
-}
-
-#endif
-#endif