Lazily and dynamically create i386-linux target descriptions

Instead of using pre-generated target descriptions, this patch
changes GDB to lazily and dynamically create target descriptions
according to the target hardware capability (xcr0 in i386).
This support any combination of target features.

Some reg in target description has "regnum" attribute, so its register
number is got from the attribute value instead from sequential allocation.

  <reg name="xmm0" bitsize="128" type="vec128" regnum="32"/>

when target description is created, it should match the regnum, so this
patch adds a new field m_next_regnum to track it, if attribute number is
greater than the m_next_regnum, print the code to set register number
explicitly.

gdb:

2017-07-26  Yao Qi  <yao.qi@linaro.org>

	* i386-linux-tdep.c: Don't include features/i386/i386-*linux.c.
	Include features/i386/32bit-*.c.
	(i386_linux_read_description): Generate target description if it
	doesn't exist.
	(_initialize_i386_linux_tdep): Don't call _initialize_tdesc_i386
	functions.
	* features/i386/32bit-linux.c: Re-generated.
	* features/i386/32bit-sse.c: Likewise.
	* target-descriptions.c (print_c_feature::visit): Print code to
	set register number if needed.
	(print_c_feature) <m_next_regnum>: New field.

5 files changed, 112 insertions, 34 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0f4ec46..77c74f2 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,19 @@
 2017-07-26  Yao Qi  <yao.qi@linaro.org>
 
+	* i386-linux-tdep.c: Don't include features/i386/i386-*linux.c.
+	Include features/i386/32bit-*.c.
+	(i386_linux_read_description): Generate target description if it
+	doesn't exist.
+	(_initialize_i386_linux_tdep): Don't call _initialize_tdesc_i386
+	functions.
+	* features/i386/32bit-linux.c: Re-generated.
+	* features/i386/32bit-sse.c: Likewise.
+	* target-descriptions.c (print_c_feature::visit): Print code to
+	set register number if needed.
+	(print_c_feature) <m_next_regnum>: New field.
+
+2017-07-26  Yao Qi  <yao.qi@linaro.org>
+
 	* features/Makefile (CFILES): Rename with TDESC_CFILES.
 	(FEATURE_XMLFILES): New.
 	(FEATURE_CFILES): New.
diff --git a/gdb/features/i386/32bit-linux.c b/gdb/features/i386/32bit-linux.c
index 686a2f1..1b50882 100644
--- a/gdb/features/i386/32bit-linux.c
+++ b/gdb/features/i386/32bit-linux.c
@@ -9,6 +9,7 @@ create_feature_i386_32bit_linux (struct target_desc *result, long regnum)
   struct tdesc_feature *feature;
 
   feature = tdesc_create_feature (result, "org.gnu.gdb.i386.linux");
+  regnum = 41;
   tdesc_create_reg (feature, "orig_eax", regnum++, 1, NULL, 32, "int");
   return regnum;
 }
diff --git a/gdb/features/i386/32bit-sse.c b/gdb/features/i386/32bit-sse.c
index 032623e..c0684fb 100644
--- a/gdb/features/i386/32bit-sse.c
+++ b/gdb/features/i386/32bit-sse.c
@@ -61,6 +61,7 @@ create_feature_i386_32bit_sse (struct target_desc *result, long regnum)
   tdesc_add_flag (type, 12, "PM");
   tdesc_add_flag (type, 15, "FZ");
 
+  regnum = 32;
   tdesc_create_reg (feature, "xmm0", regnum++, 1, NULL, 128, "vec128");
   tdesc_create_reg (feature, "xmm1", regnum++, 1, NULL, 128, "vec128");
   tdesc_create_reg (feature, "xmm2", regnum++, 1, NULL, 128, "vec128");
diff --git a/gdb/i386-linux-tdep.c b/gdb/i386-linux-tdep.c
index e986d6f..4c0f597 100644
--- a/gdb/i386-linux-tdep.c
+++ b/gdb/i386-linux-tdep.c
@@ -45,13 +45,14 @@
 
 #include "record-full.h"
 #include "linux-record.h"
-#include "features/i386/i386-linux.c"
-#include "features/i386/i386-mmx-linux.c"
-#include "features/i386/i386-mpx-linux.c"
-#include "features/i386/i386-avx-mpx-linux.c"
-#include "features/i386/i386-avx-linux.c"
-#include "features/i386/i386-avx-avx512-linux.c"
-#include "features/i386/i386-avx-mpx-avx512-pku-linux.c"
+
+#include "features/i386/32bit-core.c"
+#include "features/i386/32bit-sse.c"
+#include "features/i386/32bit-linux.c"
+#include "features/i386/32bit-avx.c"
+#include "features/i386/32bit-mpx.c"
+#include "features/i386/32bit-avx512.c"
+#include "features/i386/32bit-pkeys.c"
 
 /* Return non-zero, when the register is in the corresponding register
    group.  Put the LINUX_ORIG_EAX register in the system group.  */
@@ -683,27 +684,50 @@ i386_linux_core_read_xcr0 (bfd *abfd)
 const struct target_desc *
 i386_linux_read_description (uint64_t xcr0)
 {
-  switch ((xcr0 & X86_XSTATE_ALL_MASK))
+  if (xcr0 == 0)
+    return NULL;
+
+  static struct target_desc *i386_linux_tdescs \
+    [2/*X87*/][2/*SSE*/][2/*AVX*/][2/*MPX*/][2/*AVX512*/][2/*PKRU*/] = {};
+  struct target_desc **tdesc;
+
+  tdesc = &i386_linux_tdescs[(xcr0 & X86_XSTATE_X87) ? 1 : 0]
+    [(xcr0 & X86_XSTATE_SSE) ? 1 : 0]
+    [(xcr0 & X86_XSTATE_AVX) ? 1 : 0]
+    [(xcr0 & X86_XSTATE_MPX) ? 1 : 0]
+    [(xcr0 & X86_XSTATE_AVX512) ? 1 : 0]
+    [(xcr0 & X86_XSTATE_PKRU) ? 1 : 0];
+
+  if (*tdesc == NULL)
     {
-    case X86_XSTATE_AVX_MPX_AVX512_PKU_MASK:
-      return tdesc_i386_avx_mpx_avx512_pku_linux;
-    case X86_XSTATE_AVX_AVX512_MASK:
-      return tdesc_i386_avx_avx512_linux;
-    case X86_XSTATE_MPX_MASK:
-      return tdesc_i386_mpx_linux;
-    case X86_XSTATE_AVX_MPX_MASK:
-      return tdesc_i386_avx_mpx_linux;
-    case X86_XSTATE_AVX_MASK:
-      return tdesc_i386_avx_linux;
-    case X86_XSTATE_SSE_MASK:
-      return tdesc_i386_linux;
-    case X86_XSTATE_X87_MASK:
-      return tdesc_i386_mmx_linux;
-    default:
-      break;
+      *tdesc = allocate_target_description ();
+      set_tdesc_architecture (*tdesc, bfd_scan_arch ("i386"));
+      set_tdesc_osabi (*tdesc, osabi_from_tdesc_string ("GNU/Linux"));
+
+      long regnum = 0;
+
+      if (xcr0 & X86_XSTATE_X87)
+	regnum = create_feature_i386_32bit_core (*tdesc, regnum);
+
+      if (xcr0 & X86_XSTATE_SSE)
+	regnum = create_feature_i386_32bit_sse (*tdesc, regnum);
+
+      regnum = create_feature_i386_32bit_linux (*tdesc, regnum);
+
+      if (xcr0 & X86_XSTATE_AVX)
+	regnum = create_feature_i386_32bit_avx (*tdesc, regnum);
+
+      if (xcr0 & X86_XSTATE_MPX)
+	regnum = create_feature_i386_32bit_mpx (*tdesc, regnum);
+
+      if (xcr0 & X86_XSTATE_AVX512)
+	regnum = create_feature_i386_32bit_avx512 (*tdesc, regnum);
+
+      if (xcr0 & X86_XSTATE_PKRU)
+	regnum = create_feature_i386_32bit_pkeys (*tdesc, regnum);
     }
 
-  return NULL;
+  return *tdesc;
 }
 
 /* Get Linux/x86 target description from core dump.  */
@@ -1092,13 +1116,4 @@ _initialize_i386_linux_tdep (void)
 {
   gdbarch_register_osabi (bfd_arch_i386, 0, GDB_OSABI_LINUX,
 			  i386_linux_init_abi);
-
-  /* Initialize the Linux target description.  */
-  initialize_tdesc_i386_linux ();
-  initialize_tdesc_i386_mmx_linux ();
-  initialize_tdesc_i386_avx_linux ();
-  initialize_tdesc_i386_mpx_linux ();
-  initialize_tdesc_i386_avx_mpx_linux ();
-  initialize_tdesc_i386_avx_avx512_linux ();
-  initialize_tdesc_i386_avx_mpx_avx512_pku_linux ();
 }
diff --git a/gdb/target-descriptions.c b/gdb/target-descriptions.c
index 5fd07ef..333cbd8 100644
--- a/gdb/target-descriptions.c
+++ b/gdb/target-descriptions.c
@@ -2104,6 +2104,48 @@ public:
 
   void visit (const tdesc_reg *reg) override
   {
+    /* Most "reg" in XML target descriptions don't have "regnum"
+       attribute, so the register number is allocated sequentially.
+       In case that reg has "regnum" attribute, register number
+       should be set by that explicitly.  */
+
+    if (reg->target_regnum < m_next_regnum)
+      {
+	/* The integrity check, it can catch some errors on register
+	   number collision, like this,
+
+	  <reg name="x0" bitsize="32"/>
+	  <reg name="x1" bitsize="32"/>
+	  <reg name="x2" bitsize="32"/>
+	  <reg name="x3" bitsize="32"/>
+	  <reg name="ps" bitsize="32" regnum="3"/>
+
+	  but it also has false negatives.  The target description
+	  below is correct,
+
+	  <reg name="x1" bitsize="32" regnum="1"/>
+	  <reg name="x3" bitsize="32" regnum="3"/>
+	  <reg name="x2" bitsize="32" regnum="2"/>
+	  <reg name="x4" bitsize="32" regnum="4"/>
+
+	  but it is not a good practice, so still error on this,
+	  and also print the message so that it can be saved in the
+	  generated c file.  */
+
+	printf_unfiltered ("ERROR: \"regnum\" attribute %ld ",
+			   reg->target_regnum);
+	printf_unfiltered ("is not the largest number (%d).\n",
+			   m_next_regnum);
+	error (_("\"regnum\" attribute %ld is not the largest number (%d)."),
+	       reg->target_regnum, m_next_regnum);
+      }
+
+    if (reg->target_regnum > m_next_regnum)
+      {
+	printf_unfiltered ("  regnum = %ld;\n", reg->target_regnum);
+	m_next_regnum = reg->target_regnum;
+      }
+
     printf_unfiltered ("  tdesc_create_reg (feature, \"%s\", regnum++, %d, ",
 		       reg->name, reg->save_restore);
     if (reg->group)
@@ -2111,8 +2153,13 @@ public:
     else
       printf_unfiltered ("NULL, ");
     printf_unfiltered ("%d, \"%s\");\n", reg->bitsize, reg->type);
+
+    m_next_regnum++;
   }
 
+private:
+  /* The register number to use for the next register we see.  */
+  int m_next_regnum = 0;
 };
 
 static void