2005-07-28 Graydon Hoare <graydon@redhat.com>

	* elaborate.cxx (derived_probe::derived_probe): Accept NULL probe.
	* staptree.cxx (provide, require): Move from here...
	* staptree.h: to here, and virtualize deep-copy methods.
	* translate.cxx
	(c_unparser::emit_common_header): Include loc2c-runtime.h
	* tapsets.cxx
	(dwflpp::iterate_over_modules): Use new, faster getmodules loop.
	(dwflpp::literal_stmt_for_local): New method, call loc2c.
	(var_expanding_copy_visitor): New struct which expands $-vars.
	(dwarf_derived_probe): Rebuild this->body using var expander.
	(query_function): Refactor logic a bit for speed.
	* loc2c.{c,h}: Copies (with minor changes) of Roland's work
	from elfutils CVS.
	* Makefile.am (AM_CFLAGS): Set to elfutils-style.
	(stap_SOURCES): Add loc2c.c.
	* Makefile.in: Regenerate.

2005-07-28  Graydon Hoare  <graydon@redhat.com>

	* loc2c-runtime.h: New file from elfutils CVS.

1 files changed, 1398 insertions, 0 deletions

diff --git a/loc2c.c b/loc2c.c
new file mode 100644
index 00000000..86e7e82d
--- /dev/null
+++ b/loc2c.c
@@ -0,0 +1,1398 @@
+#include <config.h>
+#include <inttypes.h>
+#include <stdbool.h>
+#include <obstack.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <error.h>
+#include <dwarf.h>
+#include <libdw.h>
+#include <assert.h>
+
+#define _(x) x
+
+#define STACK_TYPE	"intptr_t"  /* Must be the signed type.  */
+#define UTYPE		"uintptr_t" /* Must be the unsigned type.  */
+#define SFORMAT		"%" PRId64 "L"
+#define UFORMAT		"%" PRIu64 "UL"
+#define AFORMAT		"%#" PRIx64 "UL"
+#define STACKFMT	"s%u"
+
+struct location
+{
+  struct location *next;
+
+  const Dwarf_Loc *ops;
+  size_t nops;
+
+  Dwarf_Word byte_size;
+
+  enum { loc_address, loc_register, loc_noncontiguous, loc_final } type;
+  union
+  {
+    struct			/* loc_address or loc_final */
+    {
+      char *program;		/* C fragment, leaves address in s0.  */
+      unsigned int stack_depth;	/* Temporaries "s0..<N>" used by it.  */
+      struct location *frame_base;
+      bool used_deref;		/* Program uses "deref" macro.  */
+    } address;
+    unsigned int regno;		/* loc_register */
+    struct location *pieces;	/* loc_noncontiguous */
+  };
+};
+
+
+static const char *
+dwarf_diename_integrate (Dwarf_Die *die)
+{
+  Dwarf_Attribute attr_mem;
+  return dwarf_formstring (dwarf_attr_integrate (die, DW_AT_name, &attr_mem));
+}
+
+/* Synthesize a new loc_address using the program on the obstack.  */
+static struct location *
+new_synthetic_loc (struct obstack *pool, struct location *origin, bool deref)
+{
+  obstack_1grow (pool, '\0');
+  char *program = obstack_finish (pool);
+
+  struct location *loc = obstack_alloc (pool, sizeof *loc);
+  loc->next = NULL;
+  loc->byte_size = 0;
+  loc->type = loc_address;
+  loc->address.program = program;
+  loc->address.stack_depth = 0;
+  loc->address.frame_base = NULL;
+  loc->address.used_deref = deref;
+
+  if (origin->type == loc_register)
+    {
+      loc->ops = origin->ops;
+      loc->nops = origin->nops;
+    }
+  else
+    {
+      loc->ops = NULL;
+      loc->nops = 0;
+    }
+
+  return loc;
+}
+
+
+/* Die in the middle of an expression.  */
+static struct location *
+lose (const char *failure, const Dwarf_Loc *lexpr, size_t i)
+{
+  error (2, 0, _("%s in DWARF expression [%Zu] at %" PRIu64
+		 " (%#x: %" PRId64 ", %" PRId64 ")"),
+	 failure, i, lexpr[i].offset,
+	 lexpr[i].atom, lexpr[i].number, lexpr[i].number2);
+  return NULL;
+}
+
+/* Translate a (constrained) DWARF expression into C code
+   emitted to the obstack POOL.  INDENT is the number of indentation levels.
+   ADDRBIAS is the difference between runtime and Dwarf info addresses.
+   INPUT is null or an expression to be initially pushed on the stack.
+   If NEED_FB is null, fail on DW_OP_fbreg, else set *NEED_FB to true
+   and emit "frame_base" for it.  On success, set *MAX_STACK to the number
+   of stack slots required.  On failure, set *LOSER to the index in EXPR
+   of the operation we could not handle.
+
+   Returns a failure message or null for success.  */
+
+static const char *
+translate (struct obstack *pool, int indent, Dwarf_Addr addrbias,
+	   const Dwarf_Loc *expr, const size_t len,
+	   struct location *input,
+	   bool *need_fb, size_t *loser,
+	   struct location *loc)
+{
+  loc->ops = expr;
+  loc->nops = len;
+
+#define DIE(msg) return (*loser = i, _(msg))
+
+#define emit(fmt, ...) obstack_printf (pool, fmt, ## __VA_ARGS__)
+
+  unsigned int stack_depth = 0, max_stack = 0;
+  inline void deepen (void)
+    {
+      if (stack_depth == max_stack)
+	++max_stack;
+    }
+
+#define POP(var)							      \
+    if (stack_depth > 0)						      \
+      --stack_depth;							      \
+    else if (tos_register != -1)					      \
+      fetch_tos_register ();						      \
+    else								      \
+      goto underflow;							      \
+    int var = stack_depth
+#define PUSH 		(deepen (), stack_depth++)
+#define STACK(idx)	(stack_depth - 1 - (idx))
+
+  /* Don't put stack operations in the arguments to this.  */
+#define push(fmt, ...) \
+  emit ("%*s" STACKFMT " = " fmt ";\n", indent * 2, "", PUSH, ## __VA_ARGS__)
+
+  int tos_register = -1;
+  inline void fetch_tos_register (void)
+    {
+      deepen ();
+      emit ("%*s" STACKFMT " = fetch_register (%d);\n",
+	    indent * 2, "", stack_depth, tos_register);
+      tos_register = -1;
+    }
+
+  if (input != NULL)
+    switch (input->type)
+      {
+      case loc_address:
+	push ("addr");
+	break;
+
+      case loc_register:
+	tos_register = input->regno;
+	break;
+
+      default:
+	abort ();
+	break;
+      }
+
+  size_t i;
+
+  inline const char *finish (struct location *piece)
+    {
+      if (stack_depth > 1)
+	DIE ("multiple values left on stack");
+      if (stack_depth == 1)
+	{
+	  obstack_1grow (pool, '\0');
+	  char *program = obstack_finish (pool);
+	  piece->type = loc_address;
+	  piece->address.program = program;
+	  piece->address.stack_depth = max_stack;
+	  piece->address.frame_base = NULL;
+	}
+      else if (tos_register == -1)
+	DIE ("stack underflow");
+      else if (obstack_object_size (pool) != 0)
+	DIE ("register value must stand alone in location expression");
+      else
+	{
+	  piece->type = loc_register;
+	  piece->regno = tos_register;
+	}
+      return NULL;
+    }
+
+  struct location *pieces = NULL, **tailpiece = &pieces;
+  size_t piece_expr_start = 0;
+  for (i = 0; i < len; ++i)
+    {
+      unsigned int reg;
+      uint_fast8_t sp;
+      Dwarf_Word value;
+
+      switch (expr[i].atom)
+	{
+	  /* Basic stack operations.  */
+	case DW_OP_nop:
+	  break;
+
+	case DW_OP_dup:
+	  if (stack_depth < 1)
+	    goto underflow;
+	  else
+	    {
+	      unsigned int tos = STACK (0);
+	      push (STACKFMT, tos);
+	    }
+	  break;
+
+	case DW_OP_drop:
+	  POP (ignore);
+	  emit ("%*s/* drop " STACKFMT "*/\n", indent * 2, "", ignore);
+	  break;
+
+	case DW_OP_pick:
+	  sp = expr[i].number;
+	op_pick:
+	  if (sp >= stack_depth)
+	    goto underflow;
+	  sp = STACK (sp);
+	  push (STACKFMT, sp);
+	  break;
+
+	case DW_OP_over:
+	  sp = 1;
+	  goto op_pick;
+
+	case DW_OP_swap:
+	  if (stack_depth < 2)
+	    goto underflow;
+	  deepen ();		/* Use a temporary slot.  */
+	  emit ("%*s"
+		STACKFMT " = " STACKFMT ", "
+		STACKFMT " = " STACKFMT ", "
+		STACKFMT " = " STACKFMT ";\n",
+		indent * 2, "",
+		STACK (-1), STACK (0),
+		STACK (0), STACK (1),
+		STACK (1), STACK (-1));
+	  break;
+
+	case DW_OP_rot:
+	  if (stack_depth < 3)
+	    goto underflow;
+	  deepen ();		/* Use a temporary slot.  */
+	  emit ("%*s"
+		STACKFMT " = " STACKFMT ", "
+		STACKFMT " = " STACKFMT ", "
+		STACKFMT " = " STACKFMT ", "
+		STACKFMT " = " STACKFMT ";\n",
+		indent * 2, "",
+		STACK (-1), STACK (0),
+		STACK (0), STACK (1),
+		STACK (1), STACK (2),
+		STACK (3), STACK (-1));
+	  break;
+
+
+	  /* Control flow operations.  */
+	case DW_OP_skip:
+	  {
+	    Dwarf_Off target = expr[i].offset + 3 + expr[i].number;
+	    while (i + 1 < len && expr[i + 1].offset < target)
+	      ++i;
+	    if (expr[i + 1].offset != target)
+	      DIE ("invalid skip target");
+	    break;
+	  }
+
+	case DW_OP_bra:
+	  DIE ("conditional branches not supported");
+	  break;
+
+
+	  /* Memory access.  */
+	case DW_OP_deref:
+	  {
+	    POP (addr);
+	    push ("deref (sizeof (void *), " STACKFMT ")", addr);
+	    loc->address.used_deref = true;
+	  }
+	  break;
+
+	case DW_OP_deref_size:
+	  {
+	    POP (addr);
+	    push ("deref (" UFORMAT ", " STACKFMT ")",
+		  expr[i].number, addr);
+	    loc->address.used_deref = true;
+	  }
+	  break;
+
+	case DW_OP_xderef:
+	  {
+	    POP (addr);
+	    POP (as);
+	    push ("xderef (sizeof (void *), " STACKFMT ", " STACKFMT ")",
+		  addr, as);
+	    loc->address.used_deref = true;
+	  }
+	  break;
+
+	case DW_OP_xderef_size:
+	  {
+	    POP (addr);
+	    POP (as);
+	    push ("xderef (" UFORMAT ", " STACKFMT ", " STACKFMT ")",
+		  expr[i].number, addr, as);
+	    loc->address.used_deref = true;
+	  }
+	  break;
+
+	  /* Constant-value operations.  */
+
+	case DW_OP_addr:
+	  push (AFORMAT, addrbias + expr[i].number);
+	  break;
+
+	case DW_OP_lit0 ... DW_OP_lit31:
+	  value = expr[i].atom - DW_OP_lit0;
+	  goto op_const;
+
+	case DW_OP_const1u:
+	case DW_OP_const1s:
+	case DW_OP_const2u:
+	case DW_OP_const2s:
+	case DW_OP_const4u:
+	case DW_OP_const4s:
+	case DW_OP_const8u:
+	case DW_OP_const8s:
+	case DW_OP_constu:
+	case DW_OP_consts:
+	  value = expr[i].number;
+	op_const:
+	  push (SFORMAT, value);
+	  break;
+
+	  /* Arithmetic operations.  */
+#define UNOP(dw_op, c_op)						      \
+	case DW_OP_##dw_op:						      \
+	  {								      \
+	    POP (tos);							      \
+	    push ("%s (" STACKFMT ")", #c_op, tos);			      \
+	  }								      \
+	  break
+#define BINOP(dw_op, c_op)						      \
+	case DW_OP_##dw_op:						      \
+	  {								      \
+	    POP (b);							      \
+	    POP (a);							      \
+	    push (STACKFMT " %s " STACKFMT, a, #c_op, b);		      \
+	  }								      \
+	  break
+
+	  UNOP (abs, op_abs);
+	  BINOP (and, &);
+	  BINOP (div, /);
+	  BINOP (minus, -);
+	  BINOP (mod, %);
+	  BINOP (mul, *);
+	  UNOP (neg, -);
+	  UNOP (not, ~);
+	  BINOP (or, |);
+	  BINOP (plus, +);
+	  BINOP (shl, <<);
+	  BINOP (shra, >>);
+	  BINOP (xor, ^);
+
+	  /* Comparisons are binary operators too.  */
+	  BINOP (le, <=);
+	  BINOP (ge, >=);
+	  BINOP (eq, ==);
+	  BINOP (lt, <);
+	  BINOP (gt, >);
+	  BINOP (ne, !=);
+
+#undef	UNOP
+#undef	BINOP
+
+	case DW_OP_shr:
+	  {
+	    POP (b);
+	    POP (a);
+	    push ("(%s) " STACKFMT " >> (%s)" STACKFMT,
+		  UTYPE, a, UTYPE, b);
+	    break;
+	  }
+
+	case DW_OP_plus_uconst:
+	  {
+	    POP (x);
+	    push (STACKFMT " + " UFORMAT, x, expr[i].number);
+	  }
+	  break;
+
+
+	  /* Register-relative addressing.  */
+	case DW_OP_breg0 ... DW_OP_breg31:
+	  reg = expr[i].atom - DW_OP_breg0;
+	  value = expr[i].number;
+	  goto op_breg;
+
+	case DW_OP_bregx:
+	  reg = expr[i].number;
+	  value = expr[i].number2;
+	op_breg:
+	  push ("fetch_register (%u) + " SFORMAT, reg, value);
+	  break;
+
+	case DW_OP_fbreg:
+	  if (need_fb == NULL)
+	    DIE ("DW_OP_fbreg from DW_AT_frame_base");
+	  *need_fb = true;
+	  push ("frame_base + " SFORMAT, expr[i].number);
+	  break;
+
+	  /* Direct register contents.  */
+	case DW_OP_reg0 ... DW_OP_reg31:
+	  reg = expr[i].atom - DW_OP_reg0;
+	  goto op_reg;
+
+	case DW_OP_regx:
+	  reg = expr[i].number;
+	op_reg:
+	  tos_register = reg;
+	  break;
+
+	  /* Special magic.  */
+	case DW_OP_piece:
+	  if (stack_depth > 1)
+	    /* If this ever happens we could copy the program.  */
+	    DIE ("DW_OP_piece left multiple values on stack");
+	  else
+	    {
+	      struct location *piece = obstack_alloc (pool, sizeof *piece);
+	      const char *failure = finish (piece);
+	      if (failure != NULL)
+		return failure;
+
+	      piece->ops = &expr[piece_expr_start];
+	      piece->nops = i - piece_expr_start;
+	      piece_expr_start = i + 1;
+
+	      piece->byte_size = expr[i].number;
+
+	      *tailpiece = piece;
+	      tailpiece = &piece->next;
+	      piece->next = NULL;
+	    }
+	  break;
+
+	case DW_OP_push_object_address:
+	  DIE ("XXX DW_OP_push_object_address");
+	  break;
+
+	default:
+	  DIE ("unrecognized operation");
+	  break;
+	}
+    }
+
+  if (pieces == NULL)
+    return finish (loc);
+
+  if (piece_expr_start != i)
+    DIE ("extra operations after last DW_OP_piece");
+
+  loc->type = loc_noncontiguous;
+  loc->pieces = pieces;
+
+  return NULL;
+
+ underflow:
+  DIE ("stack underflow");
+
+#undef emit
+#undef push
+#undef PUSH
+#undef POP
+#undef STACK
+#undef DIE
+}
+
+/* Translate a location starting from an address or nothing.  */
+static struct location *
+location_from_address (struct obstack *pool,
+		       int indent, Dwarf_Addr dwbias,
+		       const Dwarf_Loc *expr, size_t len, Dwarf_Addr address,
+		       struct location **input, Dwarf_Attribute *fb_attr)
+{
+  bool need_fb = false;
+  size_t loser;
+  struct location *loc = obstack_alloc (pool, sizeof *loc);
+  const char *failure = translate (pool, indent + 1, dwbias, expr, len,
+				   *input, &need_fb, &loser, loc);
+  if (failure != NULL)
+    return lose (failure, expr, loser);
+
+  loc->next = NULL;
+  if (need_fb)
+    {
+      /* The main expression uses DW_OP_fbreg, so we need to compute
+	 the DW_AT_frame_base attribute expression's value first.  */
+
+      Dwarf_Loc *fb_expr;
+      size_t fb_len;
+      switch (dwarf_addrloclists (fb_attr, address - dwbias,
+				  &fb_expr, &fb_len, 1))
+	{
+	case 1:			/* Should always happen.  */
+	  if (fb_len == 0)
+	    goto fb_inaccessible;
+	  break;
+
+	default:		/* Shouldn't happen.  */
+	case -1:
+	  error (2, 0, "dwarf_addrloclists (form %#x): %s",
+		 dwarf_whatform (fb_attr), dwarf_errmsg (-1));
+	  return NULL;
+
+	case 0:			/* Shouldn't happen.  */
+	fb_inaccessible:
+	  error (2, 0, "DW_AT_frame_base not accessible at this address");
+	  return NULL;
+	}
+
+      loc->address.frame_base = obstack_alloc (pool, sizeof *loc);
+      failure = translate (pool, indent + 1, dwbias, fb_expr, fb_len, NULL,
+			   NULL, &loser, loc->address.frame_base);
+      if (failure != NULL)
+	return lose (failure, fb_expr, loser);
+    }
+
+  if (*input != NULL)
+    (*input)->next = loc;
+  *input = loc;
+
+  return loc;
+}
+
+/* Translate a location starting from a non-address "on the top of the
+   stack".  The *INPUT location is a register name or noncontiguous
+   object specification, and this expression wants to find the "address"
+   of an object relative to that "address".  */
+
+static struct location *
+location_relative (struct obstack *pool,
+		   int indent, Dwarf_Addr dwbias,
+		   const Dwarf_Loc *expr, size_t len, Dwarf_Addr address,
+		   struct location **input, Dwarf_Attribute *fb_attr)
+{
+  Dwarf_Sword *stack;
+  unsigned int stack_depth = 0, max_stack = 0;
+  inline void deepen (void)
+    {
+      if (stack_depth == max_stack)
+	{
+	  ++max_stack;
+	  obstack_blank (pool, sizeof stack[0]);
+	  stack = (void *) obstack_base (pool);
+	}
+    }
+
+#define POP(var)							      \
+    if (stack_depth > 0)						      \
+      --stack_depth;							      \
+    else								      \
+      goto underflow;							      \
+    int var = stack_depth
+#define PUSH 		(deepen (), stack_depth++)
+#define STACK(idx)	(stack_depth - 1 - (idx))
+#define STACKWORD(idx)	stack[STACK (idx)]
+
+  /* Don't put stack operations in the arguments to this.  */
+#define push(value) (stack[PUSH] = (value))
+
+  const char *failure = NULL;
+#define DIE(msg) do { failure = _(msg); goto fail; } while (0)
+
+  struct location *head = NULL;
+  size_t i;
+  for (i = 0; i < len; ++i)
+    {
+      uint_fast8_t sp;
+      Dwarf_Word value;
+
+      switch (expr[i].atom)
+	{
+	  /* Basic stack operations.  */
+	case DW_OP_nop:
+	  break;
+
+	case DW_OP_dup:
+	  if (stack_depth < 1)
+	    goto underflow;
+	  else
+	    {
+	      unsigned int tos = STACK (0);
+	      push (stack[tos]);
+	    }
+	  break;
+
+	case DW_OP_drop:
+	  if (stack_depth > 0)
+	    --stack_depth;
+	  else if (*input != NULL)
+	    /* Mark that we have consumed the input.  */
+	    *input = NULL;
+	  else
+	    /* Hits if cleared above, or if we had no input at all.  */
+	    goto underflow;
+	  break;
+
+	case DW_OP_pick:
+	  sp = expr[i].number;
+	op_pick:
+	  if (sp >= stack_depth)
+	    goto underflow;
+	  sp = STACK (sp);
+	  push (stack[sp]);
+	  break;
+
+	case DW_OP_over:
+	  sp = 1;
+	  goto op_pick;
+
+	case DW_OP_swap:
+	  if (stack_depth < 2)
+	    goto underflow;
+	  deepen ();		/* Use a temporary slot.  */
+	  STACKWORD (-1) = STACKWORD (0);
+	  STACKWORD (0) = STACKWORD (1);
+	  STACKWORD (1) = STACKWORD (-1);
+	  break;
+
+	case DW_OP_rot:
+	  if (stack_depth < 3)
+	    goto underflow;
+	  deepen ();		/* Use a temporary slot.  */
+	  STACKWORD (-1) = STACKWORD (0);
+	  STACKWORD (0) = STACKWORD (1);
+	  STACKWORD (2) = STACKWORD (2);
+	  STACKWORD (2) = STACKWORD (-1);
+	  break;
+
+
+	  /* Control flow operations.  */
+	case DW_OP_bra:
+	  {
+	    POP (taken);
+	    if (stack[taken] == 0)
+	      break;
+	  }
+	  /*FALLTHROUGH*/
+
+	case DW_OP_skip:
+	  {
+	    Dwarf_Off target = expr[i].offset + 3 + expr[i].number;
+	    while (i + 1 < len && expr[i + 1].offset < target)
+	      ++i;
+	    if (expr[i + 1].offset != target)
+	      DIE ("invalid skip target");
+	    break;
+	  }
+
+	  /* Memory access.  */
+	case DW_OP_deref:
+	case DW_OP_deref_size:
+	case DW_OP_xderef:
+	case DW_OP_xderef_size:
+
+	  /* Register-relative addressing.  */
+	case DW_OP_breg0 ... DW_OP_breg31:
+	case DW_OP_bregx:
+	case DW_OP_fbreg:
+
+	  /* This started from a register, but now it's following a pointer.
+	     So we can do the translation starting from address here.  */
+	  return location_from_address (pool, indent, dwbias,
+					expr, len, address, input, fb_attr);
+
+
+	  /* Constant-value operations.  */
+	case DW_OP_addr:
+	  push (dwbias + expr[i].number);
+	  break;
+
+	case DW_OP_lit0 ... DW_OP_lit31:
+	  value = expr[i].atom - DW_OP_lit0;
+	  goto op_const;
+
+	case DW_OP_const1u:
+	case DW_OP_const1s:
+	case DW_OP_const2u:
+	case DW_OP_const2s:
+	case DW_OP_const4u:
+	case DW_OP_const4s:
+	case DW_OP_const8u:
+	case DW_OP_const8s:
+	case DW_OP_constu:
+	case DW_OP_consts:
+	  value = expr[i].number;
+	op_const:
+	  push (value);
+	  break;
+
+	  /* Arithmetic operations.  */
+#define UNOP(dw_op, c_op)						      \
+	case DW_OP_##dw_op:						      \
+	  {								      \
+	    POP (tos);							      \
+	    push (c_op (stack[tos])); 					      \
+	  }								      \
+	  break
+#define BINOP(dw_op, c_op)						      \
+	case DW_OP_##dw_op:						      \
+	  {								      \
+	    POP (b);							      \
+	    POP (a);							      \
+ 	    push (stack[a] c_op stack[b]);				      \
+	  }								      \
+	  break
+
+#define op_abs(x) (x < 0 ? -x : x)
+	  UNOP (abs, op_abs);
+	  BINOP (and, &);
+	  BINOP (div, /);
+	  BINOP (mod, %);
+	  BINOP (mul, *);
+	  UNOP (neg, -);
+	  UNOP (not, ~);
+	  BINOP (or, |);
+	  BINOP (shl, <<);
+	  BINOP (shra, >>);
+	  BINOP (xor, ^);
+
+	  /* Comparisons are binary operators too.  */
+	  BINOP (le, <=);
+	  BINOP (ge, >=);
+	  BINOP (eq, ==);
+	  BINOP (lt, <);
+	  BINOP (gt, >);
+	  BINOP (ne, !=);
+
+#undef	UNOP
+#undef	BINOP
+
+	case DW_OP_shr:
+	  {
+	    POP (b);
+	    POP (a);
+	    push ((Dwarf_Word) stack[a] >> (Dwarf_Word) stack[b]);
+	    break;
+	  }
+
+	  /* Simple addition we may be able to handle relative to
+	     the starting register name.  */
+	case DW_OP_minus:
+	  {
+	    POP (tos);
+	    value = -stack[tos];
+	    goto plus;
+	  }
+	case DW_OP_plus:
+	  {
+	    POP (tos);
+	    value = stack[tos];
+	    goto plus;
+	  }
+	case DW_OP_plus_uconst:
+	  value = expr[i].number;
+	plus:
+	  if (stack_depth > 0)
+	    {
+	      /* It's just private diddling after all.  */
+	      POP (a);
+	      push (stack[a] + value);
+	      break;
+	    }
+	  if (*input == NULL)
+	    goto underflow;
+
+	  /* This is the primary real-world case: the expression takes
+	     the input address and adds a constant offset.  */
+
+	  while ((*input)->type == loc_noncontiguous)
+	    {
+	      /* We are starting from a noncontiguous object (DW_OP_piece).
+		 Find the piece we want.  */
+
+	      struct location *piece = (*input)->pieces;
+	      while (piece != NULL && value >= piece->byte_size)
+		{
+		  value -= piece->byte_size;
+		  piece = piece->next;
+		}
+	      if (piece == NULL)
+		DIE ("offset outside available pieces");
+
+	      *input = piece;
+	    }
+
+	  switch ((*input)->type)
+	    {
+	    case loc_address:
+	      {
+		/* The piece we want is actually in memory.  Use the same
+		   program to compute the address from the preceding input.  */
+
+		struct location *loc = obstack_alloc (pool, sizeof *loc);
+		*loc = **input;
+		if (head == NULL)
+		  head = loc;
+		(*input)->next = loc;
+		if (value == 0)
+		  {
+		    /* The piece addresses exactly where we want to go.  */
+		    loc->next = NULL;
+		    *input = loc;
+		  }
+		else
+		  {
+		    /* Add a second fragment to offset the piece address.  */
+		    obstack_printf (pool, "%*saddr += " SFORMAT "\n",
+				    indent * 2, "", value);
+		    *input = loc->next = new_synthetic_loc (pool, *input,
+							    false);
+		  }
+
+		if (i + 1 < len)
+		  {
+		    /* This expression keeps going, but further
+		       computations now have an address to start with.
+		       So we can punt to the address computation generator.  */
+		    loc = location_from_address (pool, indent, dwbias,
+						 &expr[i + 1], len - i - 1,
+						 address, input, fb_attr);
+		    if (loc == NULL)
+		      return NULL;
+		  }
+
+		/* That's all she wrote.  */
+		return head;
+	      }
+
+	    case loc_register:
+	      // XXX
+
+	    default:
+	      abort ();
+	    }
+	  break;
+
+	  /* Direct register contents.  */
+	case DW_OP_reg0 ... DW_OP_reg31:
+	case DW_OP_regx:
+	  DIE ("register");
+	  break;
+
+	  /* Special magic.  */
+	case DW_OP_piece:
+	  DIE ("DW_OP_piece");
+	  break;
+
+	case DW_OP_push_object_address:
+	  DIE ("XXX DW_OP_push_object_address");
+	  break;
+
+	default:
+	  DIE ("unrecognized operation");
+	  break;
+	}
+    }
+
+  if (stack_depth > 1)
+    DIE ("multiple values left on stack");
+
+  if (stack_depth > 0)		/* stack_depth == 1 */
+    {
+      if (*input != NULL)
+	DIE ("multiple values left on stack");
+
+      /* Could handle this if it ever actually happened.  */
+      DIE ("relative expression computed constant");
+    }
+
+  return head;
+
+ underflow:
+  if (*input == NULL)
+    DIE ("stack underflow");
+  else
+    DIE ("cannot handle location expression");
+
+ fail:
+  return lose (failure, expr, i);
+}
+
+
+/* Translate a C fragment for the location expression, using *INPUT
+   as the starting location, begin from scratch if *INPUT is null.
+   If DW_OP_fbreg is used, it may have a subfragment computing from
+   the FB_ATTR location expression.
+
+   On errors, exit and never return (XXX ?).  On success, return the
+   first fragment created, which is also chained onto (*INPUT)->next.
+   *INPUT is then updated with the new tail of that chain.  */
+
+struct location *
+c_translate_location (struct obstack *pool,
+		      int indent, Dwarf_Addr dwbias,
+		      Dwarf_Attribute *loc_attr, Dwarf_Addr address,
+		      struct location **input, Dwarf_Attribute *fb_attr)
+{
+  Dwarf_Loc *expr;
+  size_t len;
+  switch (dwarf_addrloclists (loc_attr, address - dwbias, &expr, &len, 1))
+    {
+    case 1:			/* Should always happen.  */
+      if (len == 0)
+	goto inaccessible;
+      break;
+
+    default:			/* Shouldn't happen.  */
+    case -1:
+      error (2, 0, "dwarf_addrloclists (form %#x): %s",
+	     dwarf_whatform (fb_attr), dwarf_errmsg (-1));
+      return NULL;
+
+    case 0:			/* Shouldn't happen.  */
+    inaccessible:
+      error (2, 0, "not accessible at this address");
+      return NULL;
+    }
+
+  ++indent;
+  switch (*input == NULL ? loc_address : (*input)->type)
+    {
+    case loc_address:
+      /* We have a previous address computation.
+	 This expression will compute starting with that on the stack.  */
+      return location_from_address (pool, indent, dwbias, expr, len, address,
+				    input, fb_attr);
+
+    case loc_noncontiguous:
+    case loc_register:
+      /* The starting point is not an address computation, but a
+	 register.  We can only handle limited computations from here.  */
+      return location_relative (pool, indent, dwbias, expr, len, address,
+				input, fb_attr);
+
+    case loc_final:		/* Bogus caller.  */
+    default:
+      abort ();
+      break;
+    }
+
+  return NULL;
+}
+
+
+/* Emit "uintNN_t TARGET = ...;".  */
+static bool
+emit_base_fetch (struct obstack *pool, Dwarf_Word byte_size,
+		 const char *target, bool decl, struct location *loc)
+{
+  if (decl)
+    obstack_printf (pool, "uint%" PRIu64 "_t ", byte_size * 8);
+
+  switch (loc->type)
+    {
+    case loc_address:
+      if (byte_size != 0 && byte_size != (Dwarf_Word) -1)
+	obstack_printf (pool, "%s = deref (%" PRIu64 ", addr); ",
+			target, byte_size);
+      else
+	obstack_printf (pool, "%s = deref (sizeof %s, addr); ",
+			target, target);
+      return true;
+
+    case loc_register:
+      obstack_printf (pool, "%s = fetch_register (%u);", target, loc->regno);
+      break;
+
+    case loc_noncontiguous:
+      /* Could be handled if it ever happened.  */
+      error (2, 0, _("noncontiguous locations not supported"));
+      break;
+
+    default:
+      abort ();
+      break;
+    }
+
+  return false;
+}
+
+/* Translate a fragment to dereference the given pointer type,
+   where *INPUT is the location of the pointer with that type.
+
+   We chain on a loc_address program that yields this pointer value
+   (i.e. the location of what it points to).  */
+
+void
+c_translate_pointer (struct obstack *pool, int indent,
+		     Dwarf_Addr dwbias __attribute__ ((unused)),
+		     Dwarf_Die *typedie, struct location **input)
+{
+  obstack_printf (pool, "%*s{ ", (indent + 2) * 2, "");
+
+  bool deref = false;
+  Dwarf_Attribute attr_mem;
+  Dwarf_Word byte_size;
+  if (dwarf_attr_integrate (typedie, DW_AT_byte_size, &attr_mem) == NULL)
+    {
+      obstack_printf (pool, "uintptr_t ");
+      emit_base_fetch (pool, 0, "tmp", false, *input);
+    }
+  else if (dwarf_formudata (&attr_mem, &byte_size) != 0)
+    error (2, 0,
+	   _("cannot get byte_size attribute for type %s: %s"),
+	   dwarf_diename_integrate (typedie) ?: "<anonymous>",
+	   dwarf_errmsg (-1));
+  else
+    deref = emit_base_fetch (pool, byte_size, "tmp", true, *input);
+
+  obstack_printf (pool, " addr = tmp; }\n");
+
+  struct location *loc = new_synthetic_loc (pool, *input, deref);
+  (*input)->next = loc;
+  *input = loc;
+}
+
+/* Determine the byte size of a base type.  */
+static Dwarf_Word
+base_byte_size (Dwarf_Die *typedie)
+{
+  Dwarf_Attribute attr_mem;
+  Dwarf_Word size;
+  if (dwarf_attr_integrate (typedie, DW_AT_byte_size, &attr_mem) != NULL
+      && dwarf_formudata (&attr_mem, &size) == 0)
+    return size;
+
+  error (2, 0,
+	 _("cannot get byte_size attribute for type %s: %s"),
+	 dwarf_diename_integrate (typedie) ?: "<anonymous>",
+	 dwarf_errmsg (-1));
+  return -1;
+}
+
+/* Emit a code fragment like:
+	{ uintNN_t tmp = ...; S1 S2 S3, tmp, B0, Bn); }
+*/
+static void
+emit_bitfield (struct obstack *pool, int indent,
+	       Dwarf_Die *die, Dwarf_Word byte_size, struct location *loc,
+	       const char *s1, const char *s2, const char *s3)
+{
+  Dwarf_Word bit_offset, bit_size;
+  Dwarf_Attribute attr_mem;
+  if (dwarf_attr_integrate (die, DW_AT_bit_offset, &attr_mem) == NULL
+      || dwarf_formudata (&attr_mem, &bit_offset) != 0
+      || dwarf_attr_integrate (die, DW_AT_bit_size, &attr_mem) == NULL
+      || dwarf_formudata (&attr_mem, &bit_size) != 0)
+    error (2, 0, _("cannot get bit field parameters: %s"),
+	   dwarf_errmsg (-1));
+
+  /* Emit "{ uintNN_t tmp = ...;" to fetch the base type.  */
+
+  obstack_printf (pool, "%*s{ ", indent * 2, "");
+  emit_base_fetch (pool, byte_size, "tmp", true, loc);
+
+  obstack_printf (pool, "%s%s%s, tmp, %" PRIu64 ", %" PRIu64 "); }\n",
+		  s1, s2, s3, bit_offset, bit_size);
+}
+
+/* Translate a fragment to fetch the value of variable or member DIE
+   at the *INPUT location and store it in variable TARGET.  */
+
+void
+c_translate_fetch (struct obstack *pool, int indent,
+		   Dwarf_Addr dwbias __attribute__ ((unused)),
+		   Dwarf_Die *die, Dwarf_Attribute *typeattr,
+		   struct location **input, const char *target)
+{
+  ++indent;
+
+  Dwarf_Attribute size_attr;
+  Dwarf_Word byte_size;
+  if (dwarf_attr_integrate (die, DW_AT_byte_size, &size_attr) == NULL
+      || dwarf_formudata (&size_attr, &byte_size) != 0)
+    {
+      Dwarf_Die basedie;
+      if (dwarf_formref_die (typeattr, &basedie) == NULL)
+	error (2, 0, _("cannot get type of field: %s"), dwarf_errmsg (-1));
+      byte_size = base_byte_size (&basedie);
+    }
+
+  bool deref = false;
+  if (dwarf_hasattr_integrate (die, DW_AT_bit_offset))
+    /* This is a bit field.  */
+    emit_bitfield (pool, indent, die, byte_size, *input,
+		   "fetch_bitfield (", target, "");
+  else
+    switch (byte_size)
+      {
+      case 1:
+      case 2:
+      case 4:
+      case 8:
+	obstack_printf (pool, "%*s", indent * 2, "");
+	deref = emit_base_fetch (pool, byte_size, target, false, *input);
+	obstack_printf (pool, "\n");
+	break;
+
+      default:
+	/* Could handle this generating call to memcpy equivalent.  */
+	error (2, 0, _("fetch is larger than base integer types"));
+	break;
+      }
+
+  struct location *loc = new_synthetic_loc (pool, *input, deref);
+  loc->type = loc_final;
+  (*input)->next = loc;
+  *input = loc;
+}
+
+void
+c_translate_addressof (struct obstack *pool, int indent,
+		       Dwarf_Addr dwbias __attribute__ ((unused)),
+		       Dwarf_Die *die,
+		       Dwarf_Attribute *typeattr  __attribute__ ((unused)),
+		       struct location **input, const char *target)
+{
+  ++indent;
+
+  if (dwarf_hasattr_integrate (die, DW_AT_bit_offset))
+    error (2, 0, _("cannot take the address of a bit field"));
+
+  switch ((*input)->type)
+    {
+    case loc_address:
+      obstack_printf (pool, "%*s%s = addr;\n", indent * 2, "", target);
+      (*input)->next = new_synthetic_loc (pool, *input, false);
+      (*input)->next->type = loc_final;
+      break;
+
+    case loc_register:
+      error (2, 0, _("cannot take address of object in register"));
+      break;
+    case loc_noncontiguous:
+      error (2, 0, _("cannot take address of noncontiguous object"));
+      break;
+
+    default:
+      abort();
+      break;
+    }
+}
+
+
+/* Determine the element stride of an array type.  */
+static Dwarf_Word
+array_stride (Dwarf_Die *typedie)
+{
+  Dwarf_Attribute attr_mem;
+  if (dwarf_attr_integrate (typedie, DW_AT_stride_size, &attr_mem) != NULL)
+    {
+      Dwarf_Word stride;
+      if (dwarf_formudata (&attr_mem, &stride) == 0)
+	return stride;
+      error (2, 0, _("cannot get stride_size attribute array type %s: %s"),
+	     dwarf_diename_integrate (typedie) ?: "<anonymous>",
+	     dwarf_errmsg (-1));
+    }
+
+  Dwarf_Die die_mem;
+  if (dwarf_attr_integrate (typedie, DW_AT_type, &attr_mem) == NULL
+      || dwarf_formref_die (&attr_mem, &die_mem) == NULL)
+    error (2, 0, _("cannot get element type of array type %s: %s"),
+	   dwarf_diename_integrate (typedie) ?: "<anonymous>",
+	   dwarf_errmsg (-1));
+
+  if (dwarf_attr_integrate (&die_mem, DW_AT_byte_size, &attr_mem) != NULL)
+    {
+      Dwarf_Word stride;
+      if (dwarf_formudata (&attr_mem, &stride) == 0)
+	return stride;
+      error (2, 0,
+	     _("cannot get byte_size attribute for array element type %s: %s"),
+	     dwarf_diename_integrate (&die_mem) ?: "<anonymous>",
+	     dwarf_errmsg (-1));
+    }
+
+  error (2, 0, _("confused about array element size"));
+  return 0;
+}
+
+void
+c_translate_array (struct obstack *pool, int indent,
+		   Dwarf_Addr dwbias __attribute__ ((unused)),
+		   Dwarf_Die *typedie, struct location **input,
+		   const char *idx, Dwarf_Word const_idx)
+{
+  ++indent;
+
+  Dwarf_Word stride = array_stride (typedie);
+
+  struct location *loc = *input;
+  while (loc->type == loc_noncontiguous)
+    {
+      if (idx != NULL)
+	error (2, 0, _("cannot dynamically index noncontiguous array"));
+      else
+	{
+	  Dwarf_Word offset = const_idx * stride;
+	  struct location *piece = loc->pieces;
+	  while (piece != NULL && offset >= piece->byte_size)
+	    {
+	      offset -= piece->byte_size;
+	      piece = piece->next;
+	    }
+	  if (piece == NULL)
+	    error (2, 0, _("constant index is outside noncontiguous array"));
+	  if (offset % stride != 0)
+	    error (2, 0, _("noncontiguous array splits elements"));
+	  const_idx = offset / stride;
+	  loc = piece;
+	}
+    }
+
+  switch (loc->type)
+    {
+    case loc_address:
+      ++indent;
+      if (idx != NULL)
+	obstack_printf (pool, "%*saddr += %s * " UFORMAT ";\n",
+			indent * 2, "", idx, stride);
+      else
+	obstack_printf (pool, "%*saddr += " UFORMAT " * " UFORMAT ";\n",
+			indent * 2, "", const_idx, stride);
+      loc = new_synthetic_loc (pool, loc, false);
+      break;
+
+    case loc_register:
+      error (2, 0, _("cannot index array stored in a register"));
+      break;
+
+    default:
+      abort();
+      break;
+    }
+
+  (*input)->next = loc;
+  *input = (*input)->next;
+}
+
+
+/* Emitting C code for finalized fragments.  */
+
+
+#define emit(fmt, ...) fprintf (out, fmt, ## __VA_ARGS__)
+
+/* Open a block with a comment giving the original DWARF expression.  */
+static void
+emit_header (FILE *out, struct location *loc, unsigned int hindent)
+{
+  if (loc->ops == NULL)
+    emit ("%*s{ // synthesized\n", hindent * 2, "");
+  else
+    {
+      emit ("%*s{ // DWARF expression:", hindent * 2, "");
+      for (size_t i = 0; i < loc->nops; ++i)
+	{
+	  emit (" %#x", loc->ops[i].atom);
+	  if (loc->ops[i].number2 == 0)
+	    {
+	      if (loc->ops[i].number != 0)
+		emit ("(%" PRId64 ")", loc->ops[i].number);
+	    }
+	  else
+	    emit ("(%" PRId64 ",%" PRId64 ")",
+		  loc->ops[i].number, loc->ops[i].number2);
+	}
+      emit ("\n");
+    }
+}
+
+/* Emit a code fragment to assign the target variable to a register value.  */
+static void
+emit_loc_register (FILE *out, struct location *loc, unsigned int indent,
+		   const char *target)
+{
+  assert (loc->type == loc_register);
+
+  emit ("%*s%s = fetch_register (%u);\n",
+	indent * 2, "", target, loc->regno);
+}
+
+/* Emit a code fragment to assign the target variable to an address.  */
+static void
+emit_loc_address (FILE *out, struct location *loc, unsigned int indent,
+		  const char *target)
+{
+  assert (loc->type == loc_address);
+
+  if (loc->address.stack_depth == 0)
+    /* Synthetic program.  */
+    emit ("%s", loc->address.program);
+  else
+    {
+      emit ("%*s%s " STACKFMT, (indent + 1) * 2, "", STACK_TYPE, 0);
+      for (unsigned int i = 1; i < loc->address.stack_depth; ++i)
+	emit (", " STACKFMT, i);
+      emit (";\n");
+
+      emit ("%s%*s%s = " STACKFMT ";\n", loc->address.program,
+	    (indent + 1) * 2, "", target, 0);
+    }
+}
+
+/* Emit a code fragment to declare the target variable and
+   assign it to an address-sized value.  */
+static void
+emit_loc_value (FILE *out, struct location *loc, unsigned int indent,
+		const char *target, bool declare)
+{
+  if (declare)
+    emit ("%*s%s %s;\n", indent * 2, "", STACK_TYPE, target);
+
+  emit_header (out, loc, indent);
+
+  switch (loc->type)
+    {
+    default:
+      abort ();
+      break;
+
+    case loc_register:
+      emit_loc_register (out, loc, indent, target);
+      break;
+
+    case loc_address:
+      if (loc->address.frame_base != NULL)
+	emit_loc_value (out, loc->address.frame_base, indent,
+			"frame_base", true);
+      emit_loc_address (out, loc, indent, target);
+      break;
+    }
+
+  emit ("%*s}\n", indent * 2, "");
+}
+
+bool
+c_emit_location (FILE *out, struct location *loc, int indent)
+{
+  emit ("%*s{\n", indent * 2, "");
+
+  bool deref = false;
+  for (bool declare_addr = true; loc->next != NULL; loc = loc->next)
+    switch (loc->type)
+      {
+      case loc_address:
+	/* Emit the program fragment to calculate the address.  */
+	emit_loc_value (out, loc, indent + 1, "addr", declare_addr);
+	declare_addr = false;
+	deref = deref || loc->address.used_deref;
+	break;
+
+      case loc_register:
+      case loc_noncontiguous:
+	/* These don't produce any code directly.
+	   The next address/final record incorporates the value.  */
+	break;
+
+      case loc_final:		/* Should be last in chain!  */
+      default:
+	abort ();
+	break;
+      }
+
+  if (loc->type != loc_final)	/* Unfinished chain.  */
+    abort ();
+
+  emit ("%s%*s}\n", loc->address.program, indent * 2, "");
+
+  return deref;
+}
+
+#undef emit