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106 lines
4.2 KiB
Mathematica
106 lines
4.2 KiB
Mathematica
%-----------------------------------------------------------------------------%
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% vim: ft=mercury ts=4 sw=4 et
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%-----------------------------------------------------------------------------%
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% Copyright (C) 2001-2003, 2005-2007, 2010-2011 The University of Melbourne.
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% Copyright (C) 2014-2015, 2018 The Mercury team.
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% This file may only be copied under the terms of the GNU General
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% Public License - see the file COPYING in the Mercury distribution.
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%-----------------------------------------------------------------------------%
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%
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% File: wrap_blocks.m
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% Author: zs.
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%
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% The optimizations in use_local_vars.m insert into instruction sequences
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% references to temporary variables whose values need be preserved only within
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% an extended basic block. The wrap_blocks pass looks for references to
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% temporaries and introduces block instructions whenever it sees them. These
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% block instructions go from the first reference to a temporary to the end of
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% its extended basic block.
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%
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%-----------------------------------------------------------------------------%
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:- module ll_backend.wrap_blocks.
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:- interface.
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:- import_module ll_backend.llds.
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:- import_module list.
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%-----------------------------------------------------------------------------%
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:- pred wrap_blocks(list(instruction)::in, list(instruction)::out) is det.
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%-----------------------------------------------------------------------------%
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%-----------------------------------------------------------------------------%
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:- implementation.
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:- import_module ll_backend.opt_util.
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:- import_module bool.
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:- import_module int.
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:- import_module require.
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%-----------------------------------------------------------------------------%
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wrap_blocks(Instrs0, Instrs) :-
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wrap_instrs(Instrs0, 0, 0, [], Instrs).
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% R is the number of the highest numbered tempr variable seen so far;
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% R = 0 means we haven't seen any temp variables. Similarly, F is the
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% highest numbered tempf variable seen so far. RevSofar is a
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% reversed list of instructions starting with the first instruction
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% in this block that accesses a temp variable. Invariant: RevSofar
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% is always empty if R = 0 and F = 0.
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%
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:- pred wrap_instrs(list(instruction)::in, int::in, int::in,
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list(instruction)::in, list(instruction)::out) is det.
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wrap_instrs([], R, F, RevSofar, []) :-
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(
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RevSofar = [_ | _],
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unexpected($pred, "procedure ends with fallthrough")
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;
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RevSofar = [],
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( if ( R > 0 ; F > 0 ) then
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unexpected($pred, "procedure ends without closing block")
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else
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true
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)
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).
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wrap_instrs([Instr0 | Instrs0], R0, F0, RevSofar, Instrs) :-
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Instr0 = llds_instr(Uinstr0, _Comment0),
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opt_util.count_temps_instr(Uinstr0, R0, R1, F0, F1),
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( if ( R1 > 0 ; F1 > 0) then
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% We must close the block before a label, since you can jump
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% to a label from other blocks.
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%
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% Call instructions cannot fall through, but they cannot refer
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% to the temp variables declared by the block either, so we
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% close the block either just before or just after the call
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% instruction. We close the block before the call instruction,
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% because including it in the block causes the test case
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% debugger/all_solutions to fail.
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( if ( Uinstr0 = label(_) ; Uinstr0 = llcall(_, _, _, _, _, _) ) then
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list.reverse(RevSofar, BlockInstrs),
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wrap_instrs(Instrs0, 0, 0, [], Instrs1),
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BlockInstr = llds_instr(block(R1, F1, BlockInstrs), ""),
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Instrs = [BlockInstr, Instr0 | Instrs1]
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else if opt_util.can_instr_fall_through(Uinstr0) = no then
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list.reverse([Instr0 | RevSofar], BlockInstrs),
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wrap_instrs(Instrs0, 0, 0, [], Instrs1),
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BlockInstr = llds_instr(block(R1, F1, BlockInstrs), ""),
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Instrs = [BlockInstr | Instrs1]
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else
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wrap_instrs(Instrs0, R1, F1, [Instr0 | RevSofar], Instrs)
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)
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else
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wrap_instrs(Instrs0, 0, 0, [], Instrs1),
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Instrs = [Instr0 | Instrs1]
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).
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%-----------------------------------------------------------------------------%
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:- end_module ll_backend.wrap_blocks.
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%-----------------------------------------------------------------------------%
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