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Implement a new compiler option, --exec-trace-tail-rec, that preserves direct
tail recursion in det and semidet procedures even when debugging is enabled.
This should allow the debugging of programs that previously ran out of stack.
The problem arose because even a directly tail-recursive call had some code
after it: the code for the EXIT event, like this:
p:
incr_sp
fill in the usual debug slots
CALL EVENT
...
/* tail call */
move arguments to registers as usual
call p, return to p_ret
p_ret:
/* code to move output arguments to right registers is empty */
EXIT EVENT
decr_sp
return
If the new option is enabled, the compiler will now generate code like this:
p:
incr_sp
fill in the usual debug slots
fill in new "stack frame reuse count" slot with 0
CALL EVENT
p_1:
...
/* tail call */
move arguments to registers as usual
update the usual debug slots
increment the "stack frame reuse count" slot
TAILCALL EVENT
goto p_1
The new TAIL event takes place in the caller's stack frame, so that the local
variables of the caller are available. This includes the arguments of the
recursive call (though if they are unnamed variables, the debugger will not
show them). The TAIL event serves as a replacement for the CALL event
of the recursive invocation.
compiler/options.m:
Add the new option.
compiler/handle_options.m:
Handle an implication of the new option: the declarative debugger
does not (yet) understand TAIL events.
compiler/mark_tail_calls.m:
New module to mark directly tail recursive calls and the procedures
containing them as such.
compiler/hlds.m:
compiler/notes/compiler_design.html:
Mention the new module.
compiler/mercury_compile.m:
Invoke the new module when the new option asks us to.
compiler/hlds_goal.m:
Add the feature used to mark tail recursive calls for the debugger.
Rename an existing feature with a similar but not identical purpose
to avoid possible confusion.
compiler/hlds_pred.m:
Add a field to proc_infos that says whether the procedure contains
tail recursive calls.
Minor style improvements.
compiler/passes_aux.m:
Minor change to accommodate the needs of the new module.
compiler/code_info.m:
Transmit the information from mark_tail_calls to the code generator.
compiler/call_gen.m:
Implement the new option.
compiler/trace_gen.m:
Reserve the extra slot needed for the new option.
Switch to state variable notation in the code that does the slot
allocation, since this is less error-prone than the previous approach.
compiler/layout.m:
compiler/layout_out.m:
compiler/stack_layout.m:
Remember what stack slot holds the stack frame reuse counter,
for transmission to the runtime system.
compiler/proc_gen.m:
Add the new label needed for tail recursion.
Put the arguments of some procedures into a more logical order.
compiler/deep_profiling.m:
compiler/deforest.m:
compiler/saved_vars.m:
compiler/table_gen.m:
Conform to the changes above.
compiler/trace_params.m:
mdbcomp/prim_data.m:
runtime/mercury_trace_base.[ch]:
Add the new event type.
Convert mercury_trace_base.h to four-space indentation.
runtime/mercury_stack_layout.h:
Add a field to the execution trace information we have for each
procedure that gives the number of the stack slot (if any) that holds
the stack frame reuse counter. Add a macro to get the value in the
counter.
Convert this header file to four-space indentation.
runtime/mercury_stack_trace.[ch]:
When walking the stack, we now have to be prepared to encounter stack
frames that have been reused. Modify the algorithms in this module
accordingly, and modify the interfaces of the exported functions
to allow the functions' callers to behave accordingly as well.
Group the information we gather about stack frame for printing into
one structure, and document it.
Convert the header to four-space indentation.
library/exception.m:
mdbcomp/trace_counts.m:
Conform to the changes above.
In trace_counts.m, fix an apparent cut-and-paste error (that hasn't
caused any test case failures yet).
trace/mercury_trace.c:
Modify the implementation of the "next" and "finish" commands
to accommodate the possibility that the procedure at the selected
depth may have had its stack frame reused. In such cases
tests/debugger/tailrec1.{m,inp,exp,data}:
A new test case to check the handling of tail recursive procedures.
50 lines
425 B
Plaintext
50 lines
425 B
Plaintext
echo on
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register --quiet
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table_io allow
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table_io start
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context none
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break tailrec1_read_line
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continue
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finish
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print *
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stack
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stack -d
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continue
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finish
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stack
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stack -d
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continue
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finish
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continue
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finish
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step
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step
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step
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print *
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continue
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finish
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continue
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finish
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print *
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retry -f
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stack
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stack -d
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finish
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print *
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level 1
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print *
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level 2
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retry -f 3
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retry -f 1
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stack
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stack -d
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continue
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finish
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continue
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finish
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step
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next
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next 3
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delete *
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continue
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