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backend: revamp the handling of symbol types

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Currently it is the front end that passes the symbol types to the
backend.  For instance:

  %token <ival> NUM
  %type <ival> exp1 exp2
  exp1: NUM { $$ = $1; }
  exp2: NUM { $<ival>$ = $<ival>1; }

In both cases, $$ and $1 are passed to the backend as having type
'ival' resulting in code like `val.ival`.  This is troublesome in the
case of api.value.type=union, since in that the case the code this:

  %define api.value.type union
  %token <int> NUM
  %type <int> exp1 exp2
  exp1: NUM { $$ = $1; }
  exp2: NUM { $<int>$ = $<int>1; }

because in this case, since the backend does not know the symbol being
processed, it is forced to generate casts in both cases: *(int*)(&val)`.
This is unfortunate in the first case (exp1) where there is no reason
at all to use a cast instead of `val.NUM` and `val.exp1`.

So instead delegate the computation of the actual value type to the
backend: pass $<ival>$ as `symbol-number, ival` and $$ as
`symbol-number, MULL`, instead of passing `ival` before.

* src/scan-code.l (handle_action_dollar): Find the symbol the action
is about, not just its tyye.  Pass both symbol-number, and explicit
type tag ($<tag>n when there is one) to b4_lhs_value and b4_rhs_value.

* data/bison.m4 (b4_symbol_action): adjust to the new signature to
b4_dollar_pushdef.

* data/c-like.m4 (_b4_dollar_dollar, b4_dollar_pushdef): Accept the
symbol-number as new argument.

* data/c.m4 (b4_symbol_value): Accept the symbol-number as new
argument, and use it.
(b4_symbol_value_union): Accept the symbol-number as new
argument, and use it to prefer ready a union member rather than
casting the union.
* data/yacc.c (b4_lhs_value, b4_rhs_value): Accept the new
symbol-number argument.
Adjust uses of b4_dollar_pushdef.
* data/glr.c (b4_lhs_value, b4_rhs_value): Adjust.

* data/lalr1.cc (b4_symbol_value_template, b4_lhs_value): Adjust
to the new symbol-number argument.
* data/variant.hh (b4_symbol_value, b4_symbol_value_template): Accept
the new symbol-number argument.

* data/java.m4 (b4_symbol_value, b4_rhs_data): New.
(b4_rhs_value): Use them.
* data/lalr1.java: Adjust to b4_dollar_pushdef, and use b4_rhs_data.
This commit is contained in:
Akim Demaille
2018-12-03 07:03:29 +01:00
parent e40db8976c
commit c44a782a4e
10 changed files with 151 additions and 86 deletions
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21
data/c-like.m4
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@@ -39,25 +39,26 @@ m4_define([b4_comment],
# _b4_dollar_dollar(VALUE, FIELD, DEFAULT-FIELD)
# ----------------------------------------------
# _b4_dollar_dollar(VALUE, SYMBOL-NUM, FIELD, DEFAULT-FIELD)
# ----------------------------------------------------------
# If FIELD (or DEFAULT-FIELD) is non-null, return "VALUE.FIELD",
# otherwise just VALUE. Be sure to pass "(VALUE)" is VALUE is a
# otherwise just VALUE. Be sure to pass "(VALUE)" if VALUE is a
# pointer.
m4_define([_b4_dollar_dollar],
[b4_symbol_value([$1],
m4_if([$2], [[]],
[[$3]], [[$2]]))])
[$2],
m4_if([$3], [[]],
[[$4]], [[$3]]))])
# b4_dollar_pushdef(VALUE-POINTER, DEFAULT-FIELD, LOCATION)
# b4_dollar_pushdef(VALUE-POINTER, SYMBOL-NUM, [TYPE_TAG], LOCATION)
# b4_dollar_popdef
# ---------------------------------------------------------
# Define b4_dollar_dollar for VALUE and DEFAULT-FIELD,
# ------------------------------------------------------------------
# Define b4_dollar_dollar for VALUE-POINTER and DEFAULT-FIELD,
# and b4_at_dollar for LOCATION.
m4_define([b4_dollar_pushdef],
[m4_pushdef([b4_dollar_dollar],
[_b4_dollar_dollar([$1], m4_dquote($][1), [$2])])dnl
m4_pushdef([b4_at_dollar], [$3])dnl
[_b4_dollar_dollar([$1], [$2], m4_dquote($][1), [$3])])dnl
m4_pushdef([b4_at_dollar], [$4])dnl
])
m4_define([b4_dollar_popdef],
[m4_popdef([b4_at_dollar])dnl