gdb/config/convex/Convex.notes

   1 @c OBSOLETE
   2 @c OBSOLETE @node Convex,,, Top
   3 @c OBSOLETE @appendix Convex-specific info
   4 @c OBSOLETE @cindex Convex notes
   5 @c OBSOLETE
   6 @c OBSOLETE Scalar registers are 64 bits long, which is a pain since
   7 @c OBSOLETE left half of an S register frequently contains noise.
   8 @c OBSOLETE Therefore there are two ways to obtain the value of an S register.
   9 @c OBSOLETE
  10 @c OBSOLETE @table @kbd
  11 @c OBSOLETE @item $s0
  12 @c OBSOLETE returns the low half of the register as an int
  13 @c OBSOLETE
  14 @c OBSOLETE @item $S0
  15 @c OBSOLETE returns the whole register as a long long
  16 @c OBSOLETE @end table
  17 @c OBSOLETE
  18 @c OBSOLETE You can print the value in floating point by using @samp{p/f $s0} or @samp{p/f $S0}
  19 @c OBSOLETE to print a single or double precision value.
  20 @c OBSOLETE
  21 @c OBSOLETE @cindex vector registers
  22 @c OBSOLETE Vector registers are handled similarly, with @samp{$V0} denoting the whole
  23 @c OBSOLETE 64-bit register and @kbd{$v0} denoting the 32-bit low half; @samp{p/f $v0}
  24 @c OBSOLETE or @samp{p/f $V0} can be used to examine the register in floating point.
  25 @c OBSOLETE The length of the vector registers is taken from @samp{$vl}.
  26 @c OBSOLETE
  27 @c OBSOLETE Individual elements of a vector register are denoted in the obvious way;
  28 @c OBSOLETE @samp{print $v3[9]} prints the tenth element of register @kbd{v3}, and
  29 @c OBSOLETE @samp{set $v3[9] = 1234} alters it.
  30 @c OBSOLETE
  31 @c OBSOLETE @kbd{$vl} and @kbd{$vs} are int, and @kbd{$vm} is an int vector.
  32 @c OBSOLETE Elements of @kbd{$vm} can't be assigned to.
  33 @c OBSOLETE
  34 @c OBSOLETE @cindex communication registers
  35 @c OBSOLETE @kindex info comm-registers
  36 @c OBSOLETE Communication registers have names @kbd{$C0 .. $C63}, with @kbd{$c0 .. $c63}
  37 @c OBSOLETE denoting the low-order halves.  @samp{info comm-registers} will print them
  38 @c OBSOLETE all out, and tell which are locked.  (A communication register is
  39 @c OBSOLETE locked when a value is sent to it, and unlocked when the value is
  40 @c OBSOLETE received.)  Communication registers are, of course, global to all
  41 @c OBSOLETE threads, so it does not matter what the currently selected thread is.
  42 @c OBSOLETE @samp{info comm-reg @var{name}} prints just that one communication
  43 @c OBSOLETE register; @samp{name} may also be a communication register number
  44 @c OBSOLETE @samp{nn} or @samp{0xnn}.
  45 @c OBSOLETE @samp{info comm-reg @var{address}} prints the contents of the resource
  46 @c OBSOLETE structure at that address.
  47 @c OBSOLETE
  48 @c OBSOLETE @kindex info psw
  49 @c OBSOLETE The command @samp{info psw} prints the processor status word @kbd{$ps}
  50 @c OBSOLETE bit by bit.
  51 @c OBSOLETE
  52 @c OBSOLETE @kindex set base
  53 @c OBSOLETE GDB normally prints all integers in base 10, but the leading
  54 @c OBSOLETE @kbd{0x80000000} of pointers is intolerable in decimal, so the default
  55 @c OBSOLETE output radix has been changed to try to print addresses appropriately.
  56 @c OBSOLETE The @samp{set base} command can be used to change this.
  57 @c OBSOLETE
  58 @c OBSOLETE @table @code
  59 @c OBSOLETE @item set base 10
  60 @c OBSOLETE Integer values always print in decimal.
  61 @c OBSOLETE
  62 @c OBSOLETE @item set base 16
  63 @c OBSOLETE Integer values always print in hex.
  64 @c OBSOLETE
  65 @c OBSOLETE @item set base
  66 @c OBSOLETE Go back to the initial state, which prints integer values in hex if they
  67 @c OBSOLETE look like pointers (specifically, if they start with 0x8 or 0xf in the
  68 @c OBSOLETE stack), otherwise in decimal.
  69 @c OBSOLETE @end table
  70 @c OBSOLETE
  71 @c OBSOLETE @kindex set pipeline
  72 @c OBSOLETE When an exception such as a bus error or overflow happens, usually the PC
  73 @c OBSOLETE is several instructions ahead by the time the exception is detected.
  74 @c OBSOLETE The @samp{set pipe} command will disable this.
  75 @c OBSOLETE
  76 @c OBSOLETE @table @code
  77 @c OBSOLETE @item set pipeline off
  78 @c OBSOLETE Forces serial execution of instructions; no vector chaining and no
  79 @c OBSOLETE scalar instruction overlap.  With this, exceptions are detected with
  80 @c OBSOLETE the PC pointing to the instruction after the one in error.
  81 @c OBSOLETE
  82 @c OBSOLETE @item set pipeline on
  83 @c OBSOLETE Returns to normal, fast, execution.  This is the default.
  84 @c OBSOLETE @end table
  85 @c OBSOLETE
  86 @c OBSOLETE @cindex parallel
  87 @c OBSOLETE In a parallel program, multiple threads may be executing, each
  88 @c OBSOLETE with its own registers, stack, and local memory.  When one of them
  89 @c OBSOLETE hits a breakpoint, that thread is selected.  Other threads do
  90 @c OBSOLETE not run while the thread is in the breakpoint.
  91 @c OBSOLETE
  92 @c OBSOLETE @kindex 1cont
  93 @c OBSOLETE The selected thread can be single-stepped, given signals, and so
  94 @c OBSOLETE on.  Any other threads remain stopped.  When a @samp{cont} command is given,
  95 @c OBSOLETE all threads are resumed.  To resume just the selected thread, use
  96 @c OBSOLETE the command @samp{1cont}.
  97 @c OBSOLETE
  98 @c OBSOLETE @kindex thread
  99 @c OBSOLETE The @samp{thread} command will show the active threads and the
 100 @c OBSOLETE instruction they are about to execute.  The selected thread is marked
 101 @c OBSOLETE with an asterisk.  The command @samp{thread @var{n}} will select thread @var{n},
 102 @c OBSOLETE shifting the debugger's attention to it for single-stepping,
 103 @c OBSOLETE registers, local memory, and so on.
 104 @c OBSOLETE
 105 @c OBSOLETE @kindex info threads
 106 @c OBSOLETE The @samp{info threads} command will show what threads, if any, have
 107 @c OBSOLETE invisibly hit breakpoints or signals and are waiting to be noticed.
 108 @c OBSOLETE
 109 @c OBSOLETE @kindex set parallel
 110 @c OBSOLETE The @samp{set parallel} command controls how many threads can be active.
 111 @c OBSOLETE
 112 @c OBSOLETE @table @code
 113 @c OBSOLETE @item set parallel off
 114 @c OBSOLETE One thread.  Requests by the program that other threads join in
 115 @c OBSOLETE (spawn and pfork instructions) do not cause other threads to start up.
 116 @c OBSOLETE This does the same thing as the @samp{limit concurrency 1} command.
 117 @c OBSOLETE
 118 @c OBSOLETE @item set parallel fixed
 119 @c OBSOLETE All CPUs are assigned to your program whenever it runs.  When it
 120 @c OBSOLETE executes a pfork or spawn instruction, it begins parallel execution
 121 @c OBSOLETE immediately.  This does the same thing as the @samp{mpa -f} command.
 122 @c OBSOLETE
 123 @c OBSOLETE @item set parallel on
 124 @c OBSOLETE One or more threads.  Spawn and pfork cause CPUs to join in when and if
 125 @c OBSOLETE they are free.  This is the default.  It is very good for system
 126 @c OBSOLETE throughput, but not very good for finding bugs in parallel code.  If you
 127 @c OBSOLETE suspect a bug in parallel code, you probably want @samp{set parallel fixed.}
 128 @c OBSOLETE @end table
 129 @c OBSOLETE
 130 @c OBSOLETE @subsection Limitations
 131 @c OBSOLETE
 132 @c OBSOLETE WARNING: Convex GDB evaluates expressions in long long, because S
 133 @c OBSOLETE registers are 64 bits long.  However, GDB expression semantics are not
 134 @c OBSOLETE exactly C semantics.  This is a bug, strictly speaking, but it's not one I
 135 @c OBSOLETE know how to fix.  If @samp{x} is a program variable of type int, then it
 136 @c OBSOLETE is also type int to GDB, but @samp{x + 1} is long long, as is @samp{x + y}
 137 @c OBSOLETE or any other expression requiring computation.  So is the expression
 138 @c OBSOLETE @samp{1}, or any other constant.  You only really have to watch out for
 139 @c OBSOLETE calls.  The innocuous expression @samp{list_node (0x80001234)} has an
 140 @c OBSOLETE argument of type long long.  You must explicitly cast it to int.
 141 @c OBSOLETE
 142 @c OBSOLETE It is not possible to continue after an uncaught fatal signal by using
 143 @c OBSOLETE @samp{signal 0}, @samp{return}, @samp{jump}, or anything else.  The difficulty is with
 144 @c OBSOLETE Unix, not GDB.
 145 @c OBSOLETE
 146 @c OBSOLETE I have made no big effort to make such things as single-stepping a
 147 @c OBSOLETE @kbd{join} instruction do something reasonable.  If the program seems to
 148 @c OBSOLETE hang when doing this, type @kbd{ctrl-c} and @samp{cont}, or use
 149 @c OBSOLETE @samp{thread} to shift to a live thread.  Single-stepping a @kbd{spawn}
 150 @c OBSOLETE instruction apparently causes new threads to be born with their T bit set;
 151 @c OBSOLETE this is not handled gracefully.  When a thread has hit a breakpoint, other
 152 @c OBSOLETE threads may have invisibly hit the breakpoint in the background; if you
 153 @c OBSOLETE clear the breakpoint gdb will be surprised when threads seem to continue
 154 @c OBSOLETE to stop at it.  All of these situations produce spurious signal 5 traps;
 155 @c OBSOLETE if this happens, just type @samp{cont}.  If it becomes a nuisance, use
 156 @c OBSOLETE @samp{handle 5 nostop}.  (It will ask if you are sure.  You are.)
 157 @c OBSOLETE
 158 @c OBSOLETE There is no way in GDB to store a float in a register, as with
 159 @c OBSOLETE @kbd{set $s0 = 3.1416}.  The identifier @kbd{$s0} denotes an integer,
 160 @c OBSOLETE and like any C expression which assigns to an integer variable, the
 161 @c OBSOLETE right-hand side is casted to type int.  If you should need to do
 162 @c OBSOLETE something like this, you can assign the value to @kbd{@{float@} ($sp-4)}
 163 @c OBSOLETE and then do @kbd{set $s0 = $sp[-4]}.  Same deal with @kbd{set $v0[69] = 6.9}.
 164