164 lines
8.8 KiB
Text
164 lines
8.8 KiB
Text
@c OBSOLETE
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@c OBSOLETE @node Convex,,, Top
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@c OBSOLETE @appendix Convex-specific info
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@c OBSOLETE @cindex Convex notes
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@c OBSOLETE
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@c OBSOLETE Scalar registers are 64 bits long, which is a pain since
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@c OBSOLETE left half of an S register frequently contains noise.
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@c OBSOLETE Therefore there are two ways to obtain the value of an S register.
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@c OBSOLETE
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@c OBSOLETE @table @kbd
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@c OBSOLETE @item $s0
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@c OBSOLETE returns the low half of the register as an int
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@c OBSOLETE
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@c OBSOLETE @item $S0
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@c OBSOLETE returns the whole register as a long long
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@c OBSOLETE @end table
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@c OBSOLETE
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@c OBSOLETE You can print the value in floating point by using @samp{p/f $s0} or @samp{p/f $S0}
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@c OBSOLETE to print a single or double precision value.
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@c OBSOLETE
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@c OBSOLETE @cindex vector registers
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@c OBSOLETE Vector registers are handled similarly, with @samp{$V0} denoting the whole
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@c OBSOLETE 64-bit register and @kbd{$v0} denoting the 32-bit low half; @samp{p/f $v0}
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@c OBSOLETE or @samp{p/f $V0} can be used to examine the register in floating point.
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@c OBSOLETE The length of the vector registers is taken from @samp{$vl}.
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@c OBSOLETE
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@c OBSOLETE Individual elements of a vector register are denoted in the obvious way;
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@c OBSOLETE @samp{print $v3[9]} prints the tenth element of register @kbd{v3}, and
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@c OBSOLETE @samp{set $v3[9] = 1234} alters it.
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@c OBSOLETE
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@c OBSOLETE @kbd{$vl} and @kbd{$vs} are int, and @kbd{$vm} is an int vector.
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@c OBSOLETE Elements of @kbd{$vm} can't be assigned to.
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@c OBSOLETE
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@c OBSOLETE @cindex communication registers
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@c OBSOLETE @kindex info comm-registers
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@c OBSOLETE Communication registers have names @kbd{$C0 .. $C63}, with @kbd{$c0 .. $c63}
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@c OBSOLETE denoting the low-order halves. @samp{info comm-registers} will print them
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@c OBSOLETE all out, and tell which are locked. (A communication register is
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@c OBSOLETE locked when a value is sent to it, and unlocked when the value is
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@c OBSOLETE received.) Communication registers are, of course, global to all
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@c OBSOLETE threads, so it does not matter what the currently selected thread is.
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@c OBSOLETE @samp{info comm-reg @var{name}} prints just that one communication
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@c OBSOLETE register; @samp{name} may also be a communication register number
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@c OBSOLETE @samp{nn} or @samp{0xnn}.
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@c OBSOLETE @samp{info comm-reg @var{address}} prints the contents of the resource
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@c OBSOLETE structure at that address.
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@c OBSOLETE
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@c OBSOLETE @kindex info psw
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@c OBSOLETE The command @samp{info psw} prints the processor status word @kbd{$ps}
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@c OBSOLETE bit by bit.
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@c OBSOLETE
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@c OBSOLETE @kindex set base
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@c OBSOLETE GDB normally prints all integers in base 10, but the leading
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@c OBSOLETE @kbd{0x80000000} of pointers is intolerable in decimal, so the default
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@c OBSOLETE output radix has been changed to try to print addresses appropriately.
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@c OBSOLETE The @samp{set base} command can be used to change this.
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@c OBSOLETE
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@c OBSOLETE @table @code
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@c OBSOLETE @item set base 10
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@c OBSOLETE Integer values always print in decimal.
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@c OBSOLETE
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@c OBSOLETE @item set base 16
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@c OBSOLETE Integer values always print in hex.
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@c OBSOLETE
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@c OBSOLETE @item set base
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@c OBSOLETE Go back to the initial state, which prints integer values in hex if they
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@c OBSOLETE look like pointers (specifically, if they start with 0x8 or 0xf in the
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@c OBSOLETE stack), otherwise in decimal.
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@c OBSOLETE @end table
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@c OBSOLETE
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@c OBSOLETE @kindex set pipeline
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@c OBSOLETE When an exception such as a bus error or overflow happens, usually the PC
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@c OBSOLETE is several instructions ahead by the time the exception is detected.
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@c OBSOLETE The @samp{set pipe} command will disable this.
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@c OBSOLETE
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@c OBSOLETE @table @code
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@c OBSOLETE @item set pipeline off
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@c OBSOLETE Forces serial execution of instructions; no vector chaining and no
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@c OBSOLETE scalar instruction overlap. With this, exceptions are detected with
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@c OBSOLETE the PC pointing to the instruction after the one in error.
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@c OBSOLETE
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@c OBSOLETE @item set pipeline on
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@c OBSOLETE Returns to normal, fast, execution. This is the default.
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@c OBSOLETE @end table
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@c OBSOLETE
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@c OBSOLETE @cindex parallel
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@c OBSOLETE In a parallel program, multiple threads may be executing, each
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@c OBSOLETE with its own registers, stack, and local memory. When one of them
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@c OBSOLETE hits a breakpoint, that thread is selected. Other threads do
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@c OBSOLETE not run while the thread is in the breakpoint.
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@c OBSOLETE
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@c OBSOLETE @kindex 1cont
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@c OBSOLETE The selected thread can be single-stepped, given signals, and so
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@c OBSOLETE on. Any other threads remain stopped. When a @samp{cont} command is given,
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@c OBSOLETE all threads are resumed. To resume just the selected thread, use
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@c OBSOLETE the command @samp{1cont}.
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@c OBSOLETE
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@c OBSOLETE @kindex thread
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@c OBSOLETE The @samp{thread} command will show the active threads and the
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@c OBSOLETE instruction they are about to execute. The selected thread is marked
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@c OBSOLETE with an asterisk. The command @samp{thread @var{n}} will select thread @var{n},
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@c OBSOLETE shifting the debugger's attention to it for single-stepping,
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@c OBSOLETE registers, local memory, and so on.
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@c OBSOLETE
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@c OBSOLETE @kindex info threads
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@c OBSOLETE The @samp{info threads} command will show what threads, if any, have
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@c OBSOLETE invisibly hit breakpoints or signals and are waiting to be noticed.
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@c OBSOLETE
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@c OBSOLETE @kindex set parallel
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@c OBSOLETE The @samp{set parallel} command controls how many threads can be active.
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@c OBSOLETE
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@c OBSOLETE @table @code
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@c OBSOLETE @item set parallel off
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@c OBSOLETE One thread. Requests by the program that other threads join in
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@c OBSOLETE (spawn and pfork instructions) do not cause other threads to start up.
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@c OBSOLETE This does the same thing as the @samp{limit concurrency 1} command.
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@c OBSOLETE
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@c OBSOLETE @item set parallel fixed
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@c OBSOLETE All CPUs are assigned to your program whenever it runs. When it
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@c OBSOLETE executes a pfork or spawn instruction, it begins parallel execution
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@c OBSOLETE immediately. This does the same thing as the @samp{mpa -f} command.
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@c OBSOLETE
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@c OBSOLETE @item set parallel on
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@c OBSOLETE One or more threads. Spawn and pfork cause CPUs to join in when and if
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@c OBSOLETE they are free. This is the default. It is very good for system
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@c OBSOLETE throughput, but not very good for finding bugs in parallel code. If you
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@c OBSOLETE suspect a bug in parallel code, you probably want @samp{set parallel fixed.}
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@c OBSOLETE @end table
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@c OBSOLETE
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@c OBSOLETE @subsection Limitations
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@c OBSOLETE
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@c OBSOLETE WARNING: Convex GDB evaluates expressions in long long, because S
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@c OBSOLETE registers are 64 bits long. However, GDB expression semantics are not
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@c OBSOLETE exactly C semantics. This is a bug, strictly speaking, but it's not one I
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@c OBSOLETE know how to fix. If @samp{x} is a program variable of type int, then it
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@c OBSOLETE is also type int to GDB, but @samp{x + 1} is long long, as is @samp{x + y}
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@c OBSOLETE or any other expression requiring computation. So is the expression
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@c OBSOLETE @samp{1}, or any other constant. You only really have to watch out for
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@c OBSOLETE calls. The innocuous expression @samp{list_node (0x80001234)} has an
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@c OBSOLETE argument of type long long. You must explicitly cast it to int.
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@c OBSOLETE
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@c OBSOLETE It is not possible to continue after an uncaught fatal signal by using
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@c OBSOLETE @samp{signal 0}, @samp{return}, @samp{jump}, or anything else. The difficulty is with
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@c OBSOLETE Unix, not GDB.
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@c OBSOLETE
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@c OBSOLETE I have made no big effort to make such things as single-stepping a
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@c OBSOLETE @kbd{join} instruction do something reasonable. If the program seems to
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@c OBSOLETE hang when doing this, type @kbd{ctrl-c} and @samp{cont}, or use
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@c OBSOLETE @samp{thread} to shift to a live thread. Single-stepping a @kbd{spawn}
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@c OBSOLETE instruction apparently causes new threads to be born with their T bit set;
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@c OBSOLETE this is not handled gracefully. When a thread has hit a breakpoint, other
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@c OBSOLETE threads may have invisibly hit the breakpoint in the background; if you
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@c OBSOLETE clear the breakpoint gdb will be surprised when threads seem to continue
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@c OBSOLETE to stop at it. All of these situations produce spurious signal 5 traps;
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@c OBSOLETE if this happens, just type @samp{cont}. If it becomes a nuisance, use
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@c OBSOLETE @samp{handle 5 nostop}. (It will ask if you are sure. You are.)
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@c OBSOLETE
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@c OBSOLETE There is no way in GDB to store a float in a register, as with
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@c OBSOLETE @kbd{set $s0 = 3.1416}. The identifier @kbd{$s0} denotes an integer,
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@c OBSOLETE and like any C expression which assigns to an integer variable, the
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@c OBSOLETE right-hand side is casted to type int. If you should need to do
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@c OBSOLETE something like this, you can assign the value to @kbd{@{float@} ($sp-4)}
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@c OBSOLETE and then do @kbd{set $s0 = $sp[-4]}. Same deal with @kbd{set $v0[69] = 6.9}.
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