New instruction format 'ivABC' (a variant of iABC where parameter vC has
10 bits) allows constructors of up to 1024 elements to be coded without
EXTRAARG.
Instead of a fixed limit of 50 registers (which, in a bad worst case,
can limit the nesting of constructors to 5 levels), the compiler
computes an individual limit for each constructor based on how many
registers are available when it runs. This limit then controls the
frequency of SETLIST instructions.
Several definitions that don't need to be "global" (that is, that
concerns only specific parts of the code) moved out of llimits.h,
to more appropriate places.
- After converting a generic GCObject to a specific type ('gco2*'),
avoid using the original GCObject (to reduce aliasing).
- Small corrections in comments in 'lopcodes.h'
- Added tests about who calls __close metamethods
'simplesect' encloses the introductory text of sections with
subsections, so that each section either is all text or is all
subsections. (This commit also corrects a small brace error in the
manual and extra spaces/tabs in some other files.)
Instead of an explicit value (field 'b'), true and false use different
tag variants. This avoids reading an extra field and results in more
direct code. (Most code that uses booleans needs to distinguish between
true and false anyway.)
- Several details in 'lcode.c'
- A few more tests for code generation
- Bug in assert in 'lcode.c' ("=" x "==")
- Comments in 'lopcodes.h' and 'ltable.c'
The difference in performance between immediate operands and K operands
does not seem to justify all those extra opcodes. We only keep OP_ADDI,
due to its ubiquity and because the difference is a little more relevant.
(Later, OP_SUBI will be implemented by OP_ADDI, negating the constant.)
In arithmetic/bitwise operators, the call to metamethods is made
in a separate opcode following the main one. (The main
opcode skips this next one when the operation succeeds.) This
change reduces slightly the size of the binary and the complexity
of the arithmetic/bitwise opcodes. It also simplfies the treatment
of errors and yeld/resume in these operations, as there are much
fewer cases to consider. (Only OP_MMBIN/OP_MMBINI/OP_MMBINK,
instead of all variants of all arithmetic/bitwise operators.)
Opcodes OP_NEWTABLE and OP_SETLIST use the same representation to
store the size of the array part of a table. This new representation
can go up to 2^33 (8 + 25 bits).
OP_NEWTABLE is followed by an OP_EXTRAARG, so that it can keep
the exact size of the array part of the table to be created.
(Functions 'luaO_int2fb'/'luaO_fb2int' were removed.)
- The preprocessor must work with at least 'long', and therefore must
do shifts of up to 31 bits correctly.
- Whenever possible, use unsigned types in shifts.
When calling metamethods for things like 'a < 3.0', which generates
the opcode OP_LTI, the C register tells that the operand was
converted to an integer, so that it can be corrected to float when
calling a metamethod.
This commit also includes some other stuff:
- file 'onelua.c' added to the project
- opcode OP_PREPVARARG renamed to OP_VARARGPREP
- comparison opcodes rewritten through macros
The numerical 'for' loop over integers now uses a precomputed counter
to control its number of iteractions. This change eliminates several
weird cases caused by overflows (wrap-around) in the control variable.
(It also ensures that every integer loop halts.)
Also, the special opcodes for the usual case of step==1 were removed.
(The new code is already somewhat complex for the usual case,
but efficient.)
Several small improvements (code style, warnings, comments, more tests),
in particular:
- 'lua_topointer' extended to handle strings
- raises an error in 'string.format("%10q")' ('%q' with modifiers)
- in the manual for 'string.format', the term "option" replaced by
"conversion specifier" (the term used by the C standard)
Added opcodes for all seven arithmetic operators with K operands
(that is, operands that are numbers in the array of constants of
the function). They cover the cases of constant float operands
(e.g., 'x + .0.0', 'x^0.5') and large integer operands (e.g.,
'x % 10000').
The variable to be closed in a generic 'for' loop now is the
4th value produced in the loop initialization, instead of being
the loop state (the 2nd value produced). That allows a loop to
use a state with a '__toclose' metamethod but do not close it.
(As an example, 'f:lines()' might use the file 'f' as a state
for the loop, but it should not close the file when the loop ends.)
Added restriction that, when a label is created, there cannot be
another label with the same name visible. That allows backward goto's
to be resolved when they are read. Backward goto's get a close if
they jump out of the scope of some variable; labels get a close only
if previous goto to it jumps out of the scope of some upvalue.
Added new instruction 'OP_TFORPREP' to prepare a generic for loop.
Currently it is equivalent to a jump (but with a format 'iABx',
similar to other for-loop preparing instructions), but soon it will
be the place to create upvalues for closing loop states.
Start of the implementation of "scoped variables" or "to be closed"
variables, local variables whose '__close' (or themselves) are called
when they go out of scope. This commit implements the syntax, the
opcode, and the creation of the corresponding upvalue, but it still
does not call the finalizations when the variable goes out of scope
(the most important part).
Currently, the syntax is 'local scoped name = exp', but that will
probably change.
The array with the names of the opcodes was moved to a header file
('lopnames.h'), as it is not used by the Lua kernel. Files that need
that array ('luac.c' and 'ltests.c') include the header file to get
a private (static) copy.
