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more comments + reordeing of union inside 'expdesc' to allow 

static initialization of a VKINT value
This commit is contained in:
Roberto Ierusalimschy 2015-12-30 16:16:13 -02:00
parent c0836dda74
commit 07cf8415e3
1 changed files with 16 additions and 13 deletions
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29
lparser.h
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@ -1,5 +1,5 @@
/* /*
** $Id: lparser.h,v 1.74 2014/10/25 11:50:46 roberto Exp roberto $ ** $Id: lparser.h,v 1.75 2015/12/17 15:44:50 roberto Exp roberto $
** Lua Parser ** Lua Parser
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@ -13,15 +13,18 @@
/* /*
** Expression descriptor. ** Expression and variable descriptor.
** Code generation for expressions can be delayed to allow ** Code generation for variables and expressions can be delayed to allow
** optimizations; An 'expdesc' structure describes a ** optimizations; An 'expdesc' structure describes a potentially-delayed
** potentially-delayed expression. ** variable/expression. It has a description of its "main" value plus a
** list of conditional jumps that can also produce its value (generated
** by short-circuit operators 'and'/'or').
*/ */
/* kinds of expressions */ /* kinds of variables/expressions */
typedef enum { typedef enum {
VVOID, /* expression has no value */ VVOID, /* when 'expdesc' describes the last expression a list,
this kind means an empty list (so, no expression) */
VNIL, /* constant nil */ VNIL, /* constant nil */
VTRUE, /* constant true */ VTRUE, /* constant true */
VFALSE, /* constant false */ VFALSE, /* constant false */
@ -31,11 +34,11 @@ typedef enum {
VNONRELOC, /* expression has its value in a fixed register; VNONRELOC, /* expression has its value in a fixed register;
info = result register */ info = result register */
VLOCAL, /* local variable; info = local register */ VLOCAL, /* local variable; info = local register */
VUPVAL, /* upvalue; info = index of upvalue in 'upvalues' */ VUPVAL, /* upvalue variable; info = index of upvalue in 'upvalues' */
VINDEXED, /* indexed expression; VINDEXED, /* indexed variable;
ind.vt = whether 't' is register or upvalue; ind.vt = whether 't' is register or upvalue;
ind.t = table register or upvalue; ind.t = table register or upvalue;
ind.idx = index as R/K */ ind.idx = key's R/K index */
VJMP, /* expression is a test/comparison; VJMP, /* expression is a test/comparison;
info = pc of corresponding jump instruction */ info = pc of corresponding jump instruction */
VRELOCABLE, /* expression can put result in any register; VRELOCABLE, /* expression can put result in any register;
@ -51,14 +54,14 @@ typedef enum {
typedef struct expdesc { typedef struct expdesc {
expkind k; expkind k;
union { union {
lua_Integer ival; /* for VKINT */
lua_Number nval; /* for VKFLT */
int info; /* for generic use */
struct { /* for indexed variables (VINDEXED) */ struct { /* for indexed variables (VINDEXED) */
short idx; /* index (R/K) */ short idx; /* index (R/K) */
lu_byte t; /* table (register or upvalue) */ lu_byte t; /* table (register or upvalue) */
lu_byte vt; /* whether 't' is register (VLOCAL) or upvalue (VUPVAL) */ lu_byte vt; /* whether 't' is register (VLOCAL) or upvalue (VUPVAL) */
} ind; } ind;
int info; /* for generic use */
lua_Number nval; /* for VKFLT */
lua_Integer ival; /* for VKINT */
} u; } u;
int t; /* patch list of 'exit when true' */ int t; /* patch list of 'exit when true' */
int f; /* patch list of 'exit when false' */ int f; /* patch list of 'exit when false' */