mirror of
https://github.com/Mercury-Language/mercury.git
synced 2025-12-11 03:45:33 +00:00
4db9b2adbf
Estimated hours taken: 40
Branches: main
Until now, the only indexing we did for switches on strings was using a hash
table containing jump targets (represented as indices into a list of labels).
This diff supplements this with
- binary searches of tables containing jump targets,
- binary searches of tables containing values (lookup tables), and
- hash searches of tables containing values (lookup tables).
For now, the new methods exist in the LLDS backend only.
NEWS:
Mention the new capability.
compiler/string_switch.m:
Add predicates that implement the new indexing methods on strings.
Factor out code from existing predicates as required for this.
compiler/switch_gen.m:
Invoke the new predicates in string_switch.m when relevant.
Avoid passing the constant "no" as the initial value of !MaybeEnd
to predicates where we know this will ALWAYS happen.
compiler/options.m:
doc/user_guide.texi:
Add an option to control when we use binary searches for switches
on strings.
compiler/lookup_switch.m:
This module previously handled lookup switches on integers.
Generalize it so that pieces of it are now also usable to help
implement lookup switches on strings. Rename the predicates specific
to switches on integers to make clear this specificity, and separate
them from the predicates that help implement lookup switches on
variables of all the supported types.
Export some types, predicates and functions for use in string_switch.m.
Fix the code so that it correctly handles det switches, which
can happen e.g. if we know the possible set of values of the
switched-on variable.
Use tail-recursive code to handle the list of switch arms, to allow us
to handle very large switches.
Remove an obsolete comment from the top about a previously implemented
optimization.
compiler/lookup_util.m:
Make set_liveness_and_end_branch update MaybeEnd, to account for the
reservation of stack slots for holding the current and last rows in
later solutions tables for model_non lookup switches.
compiler/switch_util.m:
Make the exported predicates of this module more general, making them
usable for switches on strings as well as ints. Also make them easier
to use. In one case this meant bundling two predicates that were always
used together into one predicate. In another, it meant splitting one
predicate into two, since some of its callers needed an intermediate
result. In the case of a type, it means reordering its fields
to make the order match the order of their use in the implementation.
Add some predicates specifically for switches on strings.
compiler/ml_lookup_switch.m:
compiler/ml_string_switch.m:
compiler/ml_switch_gen.m:
Conform to the changes to switch_util.m.
compiler/jumpopt.m:
If the comment associated with a label ends with "nofulljump", then
inhibit fulljump optimization of jumps to that label. That
optimization would replace the jumps with the code starting at that
label. This is avoids the overhead of jump instructions, and it is a
good idea in the usual case of forward jumps. However, for the few
backward jumps we generate, the block that replaces the jump
instruction can actually END with the same jump instruction (which may
be conditionally executed), which means that our usual repeated
invocation of jumpopt can replace the original jump instruction
with MANY copies of the block it jumps to. In some cases, such as those
in hash switches, you get more copies than can ever be executed in any
actual execution. Lookup switches therefore now mark the labels that
are targets of backward jumps with this marker.
compiler/llds.m:
Document the new behavior of jumpopt.
compiler/code_info.m:
Export a predicate for use in improving the code we generate for lookup
switches.
Make some other predicates simpler and/or more efficient.
compiler/builtin_ops.m:
Add a builtin op for doing string comparisons by calling strcmp.
This is to prevent the need for two traversals of the strings being
compared in each iteration of binary search.
compiler/bytecode.m:
compiler/c_util.m:
compiler/mlds_to_gcc.m:
compiler/mlds_to_il.m:
compiler/llds.m:
compiler/llds_to_x86_64.m:
Conform to the change in builtin_ops.m.
compiler/disj_gen.m:
Conform to the change in lookup_util.m
compiler/frameopt.m:
compiler/proc_gen.m:
compiler/unify_gen.m:
Take advantage of the change in fulljump optimization.
compiler/opt_debug.m:
Improve the string representation of rvals by recording the types of
the operands of binary operations, and making the output a bit more
consistent looking.
compiler/dupproc.m:
compiler/var_locn.m:
Minor style fixes.
runtime/mercury_string.h:
Add a version of strcmp for use by our code generator. This version
casts the arguments before calling the real strcmp. We need it since we
usually specify the arguments as r1, r2 etc, which are declared as
MR_Word, not char *.
tests/hard_coded/lookup_disj.{m,exp}:
tests/hard_coded/string_switch.{m,exp}:
Make these existing tests significantly tougher by making them exercise
a wider range of use scenarios.
tests/hard_coded/string_switch{2,3}.{m,exp}:
tests/hard_coded/Mercury.options
While the string_switch test case tests the handling of jump switches,
these two new test cases test the handling of binary search tables and
hash tables respectively. Their code is identical to the code of
the string_switch test case, but Mercury.options causes them to be
compiled with different options.
tests/hard_coded/int_switch.{m,exp}:
A new test case, equivalent in structure to the string switch test
cases, to test the handling of lookup switches on atomic values.
73 lines
1.6 KiB
Plaintext
73 lines
1.6 KiB
Plaintext
jump a -> 51
|
|
jump b -> 52
|
|
jump c failed
|
|
jump aa -> 11
|
|
jump ab -> 11
|
|
jump ac failed
|
|
jump ba -> 62
|
|
jump bb -> 62
|
|
jump bc failed
|
|
jump ca -> 13
|
|
jump cb failed
|
|
jump cc failed
|
|
one a -> 1
|
|
one b -> 2
|
|
one c failed
|
|
one aa -> 11
|
|
one ab -> 11
|
|
one ac failed
|
|
one ba -> 12
|
|
one bb -> 12
|
|
one bc failed
|
|
one ca -> 13
|
|
one cb failed
|
|
one cc failed
|
|
one known a failed
|
|
one known b failed
|
|
one known c failed
|
|
one known aa -> 11
|
|
one known ab failed
|
|
one known ac failed
|
|
one known ba failed
|
|
one known bb -> 12
|
|
one known bc failed
|
|
one known ca failed
|
|
one known cb failed
|
|
one known cc failed
|
|
several a -> [1]
|
|
several b -> [2]
|
|
several c -> []
|
|
several aa -> [11, 12]
|
|
several ab -> [11, 12]
|
|
several ac -> []
|
|
several ba -> [13, 14, 15]
|
|
several bb -> [13, 14, 15]
|
|
several bc -> []
|
|
several ca -> [16]
|
|
several cb -> [16]
|
|
several cc -> []
|
|
several known a -> []
|
|
several known b -> []
|
|
several known c -> []
|
|
several known aa -> [11, 12]
|
|
several known ab -> []
|
|
several known ac -> []
|
|
several known ba -> []
|
|
several known bb -> [13, 14, 15]
|
|
several known bc -> []
|
|
several known ca -> []
|
|
several known cb -> []
|
|
several known cc -> []
|
|
several nested a -> [1001, 11001, 12001]
|
|
several nested b -> [2002, 11002, 12002]
|
|
several nested c -> []
|
|
several nested aa -> [11011, 11012, 12011, 12012]
|
|
several nested ab -> [11011, 11012, 12011, 12012]
|
|
several nested ac -> []
|
|
several nested ba -> [13013, 13014, 13015, 14013, 14014, 14015, 15013, 15014, 15015]
|
|
several nested bb -> [13013, 13014, 13015, 14013, 14014, 14015, 15013, 15014, 15015]
|
|
several nested bc -> []
|
|
several nested ca -> [16016]
|
|
several nested cb -> [16016]
|
|
several nested cc -> []
|