mirror of https://github.com/axmolengine/axmol.git
649 lines
25 KiB
C
649 lines
25 KiB
C
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/*
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** NARROW: Narrowing of numbers to integers (double to int32_t).
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** STRIPOV: Stripping of overflow checks.
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** Copyright (C) 2005-2013 Mike Pall. See Copyright Notice in luajit.h
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*/
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#define lj_opt_narrow_c
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#define LUA_CORE
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#include "lj_obj.h"
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#if LJ_HASJIT
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#include "lj_bc.h"
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#include "lj_ir.h"
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#include "lj_jit.h"
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#include "lj_iropt.h"
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#include "lj_trace.h"
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#include "lj_vm.h"
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#include "lj_strscan.h"
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/* Rationale for narrowing optimizations:
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**
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** Lua has only a single number type and this is a FP double by default.
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** Narrowing doubles to integers does not pay off for the interpreter on a
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** current-generation x86/x64 machine. Most FP operations need the same
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** amount of execution resources as their integer counterparts, except
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** with slightly longer latencies. Longer latencies are a non-issue for
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** the interpreter, since they are usually hidden by other overhead.
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**
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** The total CPU execution bandwidth is the sum of the bandwidth of the FP
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** and the integer units, because they execute in parallel. The FP units
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** have an equal or higher bandwidth than the integer units. Not using
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** them means losing execution bandwidth. Moving work away from them to
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** the already quite busy integer units is a losing proposition.
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**
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** The situation for JIT-compiled code is a bit different: the higher code
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** density makes the extra latencies much more visible. Tight loops expose
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** the latencies for updating the induction variables. Array indexing
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** requires narrowing conversions with high latencies and additional
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** guards (to check that the index is really an integer). And many common
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** optimizations only work on integers.
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**
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** One solution would be speculative, eager narrowing of all number loads.
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** This causes many problems, like losing -0 or the need to resolve type
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** mismatches between traces. It also effectively forces the integer type
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** to have overflow-checking semantics. This impedes many basic
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** optimizations and requires adding overflow checks to all integer
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** arithmetic operations (whereas FP arithmetics can do without).
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**
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** Always replacing an FP op with an integer op plus an overflow check is
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** counter-productive on a current-generation super-scalar CPU. Although
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** the overflow check branches are highly predictable, they will clog the
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** execution port for the branch unit and tie up reorder buffers. This is
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** turning a pure data-flow dependency into a different data-flow
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** dependency (with slightly lower latency) *plus* a control dependency.
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** In general, you don't want to do this since latencies due to data-flow
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** dependencies can be well hidden by out-of-order execution.
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**
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** A better solution is to keep all numbers as FP values and only narrow
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** when it's beneficial to do so. LuaJIT uses predictive narrowing for
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** induction variables and demand-driven narrowing for index expressions,
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** integer arguments and bit operations. Additionally it can eliminate or
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** hoist most of the resulting overflow checks. Regular arithmetic
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** computations are never narrowed to integers.
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**
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** The integer type in the IR has convenient wrap-around semantics and
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** ignores overflow. Extra operations have been added for
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** overflow-checking arithmetic (ADDOV/SUBOV) instead of an extra type.
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** Apart from reducing overall complexity of the compiler, this also
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** nicely solves the problem where you want to apply algebraic
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** simplifications to ADD, but not to ADDOV. And the x86/x64 assembler can
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** use lea instead of an add for integer ADD, but not for ADDOV (lea does
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** not affect the flags, but it helps to avoid register moves).
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**
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**
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** All of the above has to be reconsidered for architectures with slow FP
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** operations or without a hardware FPU. The dual-number mode of LuaJIT
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** addresses this issue. Arithmetic operations are performed on integers
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** as far as possible and overflow checks are added as needed.
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**
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** This implies that narrowing for integer arguments and bit operations
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** should also strip overflow checks, e.g. replace ADDOV with ADD. The
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** original overflow guards are weak and can be eliminated by DCE, if
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** there's no other use.
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**
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** A slight twist is that it's usually beneficial to use overflow-checked
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** integer arithmetics if all inputs are already integers. This is the only
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** change that affects the single-number mode, too.
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*/
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/* Some local macros to save typing. Undef'd at the end. */
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#define IR(ref) (&J->cur.ir[(ref)])
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#define fins (&J->fold.ins)
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/* Pass IR on to next optimization in chain (FOLD). */
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#define emitir(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_opt_fold(J))
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#define emitir_raw(ot, a, b) (lj_ir_set(J, (ot), (a), (b)), lj_ir_emit(J))
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/* -- Elimination of narrowing type conversions --------------------------- */
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/* Narrowing of index expressions and bit operations is demand-driven. The
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** trace recorder emits a narrowing type conversion (CONV.int.num or TOBIT)
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** in all of these cases (e.g. array indexing or string indexing). FOLD
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** already takes care of eliminating simple redundant conversions like
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** CONV.int.num(CONV.num.int(x)) ==> x.
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**
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** But the surrounding code is FP-heavy and arithmetic operations are
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** performed on FP numbers (for the single-number mode). Consider a common
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** example such as 'x=t[i+1]', with 'i' already an integer (due to induction
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** variable narrowing). The index expression would be recorded as
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** CONV.int.num(ADD(CONV.num.int(i), 1))
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** which is clearly suboptimal.
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**
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** One can do better by recursively backpropagating the narrowing type
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** conversion across FP arithmetic operations. This turns FP ops into
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** their corresponding integer counterparts. Depending on the semantics of
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** the conversion they also need to check for overflow. Currently only ADD
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** and SUB are supported.
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**
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** The above example can be rewritten as
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** ADDOV(CONV.int.num(CONV.num.int(i)), 1)
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** and then into ADDOV(i, 1) after folding of the conversions. The original
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** FP ops remain in the IR and are eliminated by DCE since all references to
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** them are gone.
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**
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** [In dual-number mode the trace recorder already emits ADDOV etc., but
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** this can be further reduced. See below.]
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**
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** Special care has to be taken to avoid narrowing across an operation
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** which is potentially operating on non-integral operands. One obvious
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** case is when an expression contains a non-integral constant, but ends
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** up as an integer index at runtime (like t[x+1.5] with x=0.5).
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**
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** Operations with two non-constant operands illustrate a similar problem
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** (like t[a+b] with a=1.5 and b=2.5). Backpropagation has to stop there,
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** unless it can be proven that either operand is integral (e.g. by CSEing
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** a previous conversion). As a not-so-obvious corollary this logic also
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** applies for a whole expression tree (e.g. t[(a+1)+(b+1)]).
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**
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** Correctness of the transformation is guaranteed by avoiding to expand
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** the tree by adding more conversions than the one we would need to emit
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** if not backpropagating. TOBIT employs a more optimistic rule, because
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** the conversion has special semantics, designed to make the life of the
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** compiler writer easier. ;-)
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**
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** Using on-the-fly backpropagation of an expression tree doesn't work
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** because it's unknown whether the transform is correct until the end.
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** This either requires IR rollback and cache invalidation for every
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** subtree or a two-pass algorithm. The former didn't work out too well,
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** so the code now combines a recursive collector with a stack-based
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** emitter.
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**
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** [A recursive backpropagation algorithm with backtracking, employing
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** skip-list lookup and round-robin caching, emitting stack operations
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** on-the-fly for a stack-based interpreter -- and all of that in a meager
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** kilobyte? Yep, compilers are a great treasure chest. Throw away your
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** textbooks and read the codebase of a compiler today!]
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**
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** There's another optimization opportunity for array indexing: it's
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** always accompanied by an array bounds-check. The outermost overflow
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** check may be delegated to the ABC operation. This works because ABC is
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** an unsigned comparison and wrap-around due to overflow creates negative
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** numbers.
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**
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** But this optimization is only valid for constants that cannot overflow
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** an int32_t into the range of valid array indexes [0..2^27+1). A check
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** for +-2^30 is safe since -2^31 - 2^30 wraps to 2^30 and 2^31-1 + 2^30
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** wraps to -2^30-1.
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**
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** It's also good enough in practice, since e.g. t[i+1] or t[i-10] are
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** quite common. So the above example finally ends up as ADD(i, 1)!
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**
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** Later on, the assembler is able to fuse the whole array reference and
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** the ADD into the memory operands of loads and other instructions. This
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** is why LuaJIT is able to generate very pretty (and fast) machine code
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** for array indexing. And that, my dear, concludes another story about
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** one of the hidden secrets of LuaJIT ...
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*/
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/* Maximum backpropagation depth and maximum stack size. */
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#define NARROW_MAX_BACKPROP 100
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#define NARROW_MAX_STACK 256
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/* The stack machine has a 32 bit instruction format: [IROpT | IRRef1]
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** The lower 16 bits hold a reference (or 0). The upper 16 bits hold
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** the IR opcode + type or one of the following special opcodes:
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*/
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enum {
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NARROW_REF, /* Push ref. */
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NARROW_CONV, /* Push conversion of ref. */
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NARROW_SEXT, /* Push sign-extension of ref. */
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NARROW_INT /* Push KINT ref. The next code holds an int32_t. */
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};
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typedef uint32_t NarrowIns;
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#define NARROWINS(op, ref) (((op) << 16) + (ref))
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#define narrow_op(ins) ((IROpT)((ins) >> 16))
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#define narrow_ref(ins) ((IRRef1)(ins))
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/* Context used for narrowing of type conversions. */
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typedef struct NarrowConv {
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jit_State *J; /* JIT compiler state. */
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NarrowIns *sp; /* Current stack pointer. */
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NarrowIns *maxsp; /* Maximum stack pointer minus redzone. */
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int lim; /* Limit on the number of emitted conversions. */
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IRRef mode; /* Conversion mode (IRCONV_*). */
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IRType t; /* Destination type: IRT_INT or IRT_I64. */
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NarrowIns stack[NARROW_MAX_STACK]; /* Stack holding stack-machine code. */
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} NarrowConv;
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/* Lookup a reference in the backpropagation cache. */
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static BPropEntry *narrow_bpc_get(jit_State *J, IRRef1 key, IRRef mode)
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{
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ptrdiff_t i;
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for (i = 0; i < BPROP_SLOTS; i++) {
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BPropEntry *bp = &J->bpropcache[i];
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/* Stronger checks are ok, too. */
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if (bp->key == key && bp->mode >= mode &&
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((bp->mode ^ mode) & IRCONV_MODEMASK) == 0)
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return bp;
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}
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return NULL;
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}
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/* Add an entry to the backpropagation cache. */
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static void narrow_bpc_set(jit_State *J, IRRef1 key, IRRef1 val, IRRef mode)
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{
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uint32_t slot = J->bpropslot;
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BPropEntry *bp = &J->bpropcache[slot];
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J->bpropslot = (slot + 1) & (BPROP_SLOTS-1);
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bp->key = key;
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bp->val = val;
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bp->mode = mode;
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}
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/* Backpropagate overflow stripping. */
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static void narrow_stripov_backprop(NarrowConv *nc, IRRef ref, int depth)
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{
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jit_State *J = nc->J;
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IRIns *ir = IR(ref);
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if (ir->o == IR_ADDOV || ir->o == IR_SUBOV ||
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(ir->o == IR_MULOV && (nc->mode & IRCONV_CONVMASK) == IRCONV_ANY)) {
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BPropEntry *bp = narrow_bpc_get(nc->J, ref, IRCONV_TOBIT);
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if (bp) {
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ref = bp->val;
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} else if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) {
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narrow_stripov_backprop(nc, ir->op1, depth);
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narrow_stripov_backprop(nc, ir->op2, depth);
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*nc->sp++ = NARROWINS(IRT(ir->o - IR_ADDOV + IR_ADD, IRT_INT), ref);
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return;
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}
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}
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*nc->sp++ = NARROWINS(NARROW_REF, ref);
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}
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/* Backpropagate narrowing conversion. Return number of needed conversions. */
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static int narrow_conv_backprop(NarrowConv *nc, IRRef ref, int depth)
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{
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jit_State *J = nc->J;
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IRIns *ir = IR(ref);
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IRRef cref;
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/* Check the easy cases first. */
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if (ir->o == IR_CONV && (ir->op2 & IRCONV_SRCMASK) == IRT_INT) {
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if ((nc->mode & IRCONV_CONVMASK) <= IRCONV_ANY)
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narrow_stripov_backprop(nc, ir->op1, depth+1);
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else
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*nc->sp++ = NARROWINS(NARROW_REF, ir->op1); /* Undo conversion. */
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if (nc->t == IRT_I64)
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*nc->sp++ = NARROWINS(NARROW_SEXT, 0); /* Sign-extend integer. */
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return 0;
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} else if (ir->o == IR_KNUM) { /* Narrow FP constant. */
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lua_Number n = ir_knum(ir)->n;
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if ((nc->mode & IRCONV_CONVMASK) == IRCONV_TOBIT) {
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/* Allows a wider range of constants. */
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int64_t k64 = (int64_t)n;
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if (n == (lua_Number)k64) { /* Only if const doesn't lose precision. */
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*nc->sp++ = NARROWINS(NARROW_INT, 0);
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*nc->sp++ = (NarrowIns)k64; /* But always truncate to 32 bits. */
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return 0;
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}
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} else {
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int32_t k = lj_num2int(n);
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/* Only if constant is a small integer. */
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if (checki16(k) && n == (lua_Number)k) {
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*nc->sp++ = NARROWINS(NARROW_INT, 0);
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*nc->sp++ = (NarrowIns)k;
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return 0;
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}
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}
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return 10; /* Never narrow other FP constants (this is rare). */
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}
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/* Try to CSE the conversion. Stronger checks are ok, too. */
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cref = J->chain[fins->o];
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while (cref > ref) {
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IRIns *cr = IR(cref);
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if (cr->op1 == ref &&
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(fins->o == IR_TOBIT ||
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((cr->op2 & IRCONV_MODEMASK) == (nc->mode & IRCONV_MODEMASK) &&
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irt_isguard(cr->t) >= irt_isguard(fins->t)))) {
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*nc->sp++ = NARROWINS(NARROW_REF, cref);
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return 0; /* Already there, no additional conversion needed. */
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}
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cref = cr->prev;
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}
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/* Backpropagate across ADD/SUB. */
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if (ir->o == IR_ADD || ir->o == IR_SUB) {
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/* Try cache lookup first. */
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IRRef mode = nc->mode;
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BPropEntry *bp;
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/* Inner conversions need a stronger check. */
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if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX && depth > 0)
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mode += IRCONV_CHECK-IRCONV_INDEX;
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bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode);
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if (bp) {
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*nc->sp++ = NARROWINS(NARROW_REF, bp->val);
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return 0;
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} else if (nc->t == IRT_I64) {
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/* Try sign-extending from an existing (checked) conversion to int. */
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mode = (IRT_INT<<5)|IRT_NUM|IRCONV_INDEX;
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bp = narrow_bpc_get(nc->J, (IRRef1)ref, mode);
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if (bp) {
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*nc->sp++ = NARROWINS(NARROW_REF, bp->val);
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*nc->sp++ = NARROWINS(NARROW_SEXT, 0);
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return 0;
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}
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}
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if (++depth < NARROW_MAX_BACKPROP && nc->sp < nc->maxsp) {
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NarrowIns *savesp = nc->sp;
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int count = narrow_conv_backprop(nc, ir->op1, depth);
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count += narrow_conv_backprop(nc, ir->op2, depth);
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if (count <= nc->lim) { /* Limit total number of conversions. */
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*nc->sp++ = NARROWINS(IRT(ir->o, nc->t), ref);
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return count;
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}
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nc->sp = savesp; /* Too many conversions, need to backtrack. */
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}
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}
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/* Otherwise add a conversion. */
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*nc->sp++ = NARROWINS(NARROW_CONV, ref);
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return 1;
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}
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/* Emit the conversions collected during backpropagation. */
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static IRRef narrow_conv_emit(jit_State *J, NarrowConv *nc)
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{
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/* The fins fields must be saved now -- emitir() overwrites them. */
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IROpT guardot = irt_isguard(fins->t) ? IRTG(IR_ADDOV-IR_ADD, 0) : 0;
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IROpT convot = fins->ot;
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IRRef1 convop2 = fins->op2;
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NarrowIns *next = nc->stack; /* List of instructions from backpropagation. */
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NarrowIns *last = nc->sp;
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NarrowIns *sp = nc->stack; /* Recycle the stack to store operands. */
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while (next < last) { /* Simple stack machine to process the ins. list. */
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||
|
NarrowIns ref = *next++;
|
||
|
IROpT op = narrow_op(ref);
|
||
|
if (op == NARROW_REF) {
|
||
|
*sp++ = ref;
|
||
|
} else if (op == NARROW_CONV) {
|
||
|
*sp++ = emitir_raw(convot, ref, convop2); /* Raw emit avoids a loop. */
|
||
|
} else if (op == NARROW_SEXT) {
|
||
|
lua_assert(sp >= nc->stack+1);
|
||
|
sp[-1] = emitir(IRT(IR_CONV, IRT_I64), sp[-1],
|
||
|
(IRT_I64<<5)|IRT_INT|IRCONV_SEXT);
|
||
|
} else if (op == NARROW_INT) {
|
||
|
lua_assert(next < last);
|
||
|
*sp++ = nc->t == IRT_I64 ?
|
||
|
lj_ir_kint64(J, (int64_t)(int32_t)*next++) :
|
||
|
lj_ir_kint(J, *next++);
|
||
|
} else { /* Regular IROpT. Pops two operands and pushes one result. */
|
||
|
IRRef mode = nc->mode;
|
||
|
lua_assert(sp >= nc->stack+2);
|
||
|
sp--;
|
||
|
/* Omit some overflow checks for array indexing. See comments above. */
|
||
|
if ((mode & IRCONV_CONVMASK) == IRCONV_INDEX) {
|
||
|
if (next == last && irref_isk(narrow_ref(sp[0])) &&
|
||
|
(uint32_t)IR(narrow_ref(sp[0]))->i + 0x40000000u < 0x80000000u)
|
||
|
guardot = 0;
|
||
|
else /* Otherwise cache a stronger check. */
|
||
|
mode += IRCONV_CHECK-IRCONV_INDEX;
|
||
|
}
|
||
|
sp[-1] = emitir(op+guardot, sp[-1], sp[0]);
|
||
|
/* Add to cache. */
|
||
|
if (narrow_ref(ref))
|
||
|
narrow_bpc_set(J, narrow_ref(ref), narrow_ref(sp[-1]), mode);
|
||
|
}
|
||
|
}
|
||
|
lua_assert(sp == nc->stack+1);
|
||
|
return nc->stack[0];
|
||
|
}
|
||
|
|
||
|
/* Narrow a type conversion of an arithmetic operation. */
|
||
|
TRef LJ_FASTCALL lj_opt_narrow_convert(jit_State *J)
|
||
|
{
|
||
|
if ((J->flags & JIT_F_OPT_NARROW)) {
|
||
|
NarrowConv nc;
|
||
|
nc.J = J;
|
||
|
nc.sp = nc.stack;
|
||
|
nc.maxsp = &nc.stack[NARROW_MAX_STACK-4];
|
||
|
nc.t = irt_type(fins->t);
|
||
|
if (fins->o == IR_TOBIT) {
|
||
|
nc.mode = IRCONV_TOBIT; /* Used only in the backpropagation cache. */
|
||
|
nc.lim = 2; /* TOBIT can use a more optimistic rule. */
|
||
|
} else {
|
||
|
nc.mode = fins->op2;
|
||
|
nc.lim = 1;
|
||
|
}
|
||
|
if (narrow_conv_backprop(&nc, fins->op1, 0) <= nc.lim)
|
||
|
return narrow_conv_emit(J, &nc);
|
||
|
}
|
||
|
return NEXTFOLD;
|
||
|
}
|
||
|
|
||
|
/* -- Narrowing of implicit conversions ----------------------------------- */
|
||
|
|
||
|
/* Recursively strip overflow checks. */
|
||
|
static TRef narrow_stripov(jit_State *J, TRef tr, int lastop, IRRef mode)
|
||
|
{
|
||
|
IRRef ref = tref_ref(tr);
|
||
|
IRIns *ir = IR(ref);
|
||
|
int op = ir->o;
|
||
|
if (op >= IR_ADDOV && op <= lastop) {
|
||
|
BPropEntry *bp = narrow_bpc_get(J, ref, mode);
|
||
|
if (bp) {
|
||
|
return TREF(bp->val, irt_t(IR(bp->val)->t));
|
||
|
} else {
|
||
|
IRRef op1 = ir->op1, op2 = ir->op2; /* The IR may be reallocated. */
|
||
|
op1 = narrow_stripov(J, op1, lastop, mode);
|
||
|
op2 = narrow_stripov(J, op2, lastop, mode);
|
||
|
tr = emitir(IRT(op - IR_ADDOV + IR_ADD,
|
||
|
((mode & IRCONV_DSTMASK) >> IRCONV_DSH)), op1, op2);
|
||
|
narrow_bpc_set(J, ref, tref_ref(tr), mode);
|
||
|
}
|
||
|
} else if (LJ_64 && (mode & IRCONV_SEXT) && !irt_is64(ir->t)) {
|
||
|
tr = emitir(IRT(IR_CONV, IRT_INTP), tr, mode);
|
||
|
}
|
||
|
return tr;
|
||
|
}
|
||
|
|
||
|
/* Narrow array index. */
|
||
|
TRef LJ_FASTCALL lj_opt_narrow_index(jit_State *J, TRef tr)
|
||
|
{
|
||
|
IRIns *ir;
|
||
|
lua_assert(tref_isnumber(tr));
|
||
|
if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
|
||
|
return emitir(IRTGI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_INDEX);
|
||
|
/* Omit some overflow checks for array indexing. See comments above. */
|
||
|
ir = IR(tref_ref(tr));
|
||
|
if ((ir->o == IR_ADDOV || ir->o == IR_SUBOV) && irref_isk(ir->op2) &&
|
||
|
(uint32_t)IR(ir->op2)->i + 0x40000000u < 0x80000000u)
|
||
|
return emitir(IRTI(ir->o - IR_ADDOV + IR_ADD), ir->op1, ir->op2);
|
||
|
return tr;
|
||
|
}
|
||
|
|
||
|
/* Narrow conversion to integer operand (overflow undefined). */
|
||
|
TRef LJ_FASTCALL lj_opt_narrow_toint(jit_State *J, TRef tr)
|
||
|
{
|
||
|
if (tref_isstr(tr))
|
||
|
tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
|
||
|
if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
|
||
|
return emitir(IRTI(IR_CONV), tr, IRCONV_INT_NUM|IRCONV_ANY);
|
||
|
if (!tref_isinteger(tr))
|
||
|
lj_trace_err(J, LJ_TRERR_BADTYPE);
|
||
|
/*
|
||
|
** Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV.
|
||
|
** Use IRCONV_TOBIT for the cache entries, since the semantics are the same.
|
||
|
*/
|
||
|
return narrow_stripov(J, tr, IR_MULOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT);
|
||
|
}
|
||
|
|
||
|
/* Narrow conversion to bitop operand (overflow wrapped). */
|
||
|
TRef LJ_FASTCALL lj_opt_narrow_tobit(jit_State *J, TRef tr)
|
||
|
{
|
||
|
if (tref_isstr(tr))
|
||
|
tr = emitir(IRTG(IR_STRTO, IRT_NUM), tr, 0);
|
||
|
if (tref_isnum(tr)) /* Conversion may be narrowed, too. See above. */
|
||
|
return emitir(IRTI(IR_TOBIT), tr, lj_ir_knum_tobit(J));
|
||
|
if (!tref_isinteger(tr))
|
||
|
lj_trace_err(J, LJ_TRERR_BADTYPE);
|
||
|
/*
|
||
|
** Wrapped overflow semantics allow stripping of ADDOV and SUBOV.
|
||
|
** MULOV cannot be stripped due to precision widening.
|
||
|
*/
|
||
|
return narrow_stripov(J, tr, IR_SUBOV, (IRT_INT<<5)|IRT_INT|IRCONV_TOBIT);
|
||
|
}
|
||
|
|
||
|
#if LJ_HASFFI
|
||
|
/* Narrow C array index (overflow undefined). */
|
||
|
TRef LJ_FASTCALL lj_opt_narrow_cindex(jit_State *J, TRef tr)
|
||
|
{
|
||
|
lua_assert(tref_isnumber(tr));
|
||
|
if (tref_isnum(tr))
|
||
|
return emitir(IRT(IR_CONV, IRT_INTP), tr,
|
||
|
(IRT_INTP<<5)|IRT_NUM|IRCONV_TRUNC|IRCONV_ANY);
|
||
|
/* Undefined overflow semantics allow stripping of ADDOV, SUBOV and MULOV. */
|
||
|
return narrow_stripov(J, tr, IR_MULOV,
|
||
|
LJ_64 ? ((IRT_INTP<<5)|IRT_INT|IRCONV_SEXT) :
|
||
|
((IRT_INTP<<5)|IRT_INT|IRCONV_TOBIT));
|
||
|
}
|
||
|
#endif
|
||
|
|
||
|
/* -- Narrowing of arithmetic operators ----------------------------------- */
|
||
|
|
||
|
/* Check whether a number fits into an int32_t (-0 is ok, too). */
|
||
|
static int numisint(lua_Number n)
|
||
|
{
|
||
|
return (n == (lua_Number)lj_num2int(n));
|
||
|
}
|
||
|
|
||
|
/* Narrowing of arithmetic operations. */
|
||
|
TRef lj_opt_narrow_arith(jit_State *J, TRef rb, TRef rc,
|
||
|
TValue *vb, TValue *vc, IROp op)
|
||
|
{
|
||
|
if (tref_isstr(rb)) {
|
||
|
rb = emitir(IRTG(IR_STRTO, IRT_NUM), rb, 0);
|
||
|
lj_strscan_num(strV(vb), vb);
|
||
|
}
|
||
|
if (tref_isstr(rc)) {
|
||
|
rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0);
|
||
|
lj_strscan_num(strV(vc), vc);
|
||
|
}
|
||
|
/* Must not narrow MUL in non-DUALNUM variant, because it loses -0. */
|
||
|
if ((op >= IR_ADD && op <= (LJ_DUALNUM ? IR_MUL : IR_SUB)) &&
|
||
|
tref_isinteger(rb) && tref_isinteger(rc) &&
|
||
|
numisint(lj_vm_foldarith(numberVnum(vb), numberVnum(vc),
|
||
|
(int)op - (int)IR_ADD)))
|
||
|
return emitir(IRTGI((int)op - (int)IR_ADD + (int)IR_ADDOV), rb, rc);
|
||
|
if (!tref_isnum(rb)) rb = emitir(IRTN(IR_CONV), rb, IRCONV_NUM_INT);
|
||
|
if (!tref_isnum(rc)) rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT);
|
||
|
return emitir(IRTN(op), rb, rc);
|
||
|
}
|
||
|
|
||
|
/* Narrowing of unary minus operator. */
|
||
|
TRef lj_opt_narrow_unm(jit_State *J, TRef rc, TValue *vc)
|
||
|
{
|
||
|
if (tref_isstr(rc)) {
|
||
|
rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0);
|
||
|
lj_strscan_num(strV(vc), vc);
|
||
|
}
|
||
|
if (tref_isinteger(rc)) {
|
||
|
if ((uint32_t)numberVint(vc) != 0x80000000u)
|
||
|
return emitir(IRTGI(IR_SUBOV), lj_ir_kint(J, 0), rc);
|
||
|
rc = emitir(IRTN(IR_CONV), rc, IRCONV_NUM_INT);
|
||
|
}
|
||
|
return emitir(IRTN(IR_NEG), rc, lj_ir_knum_neg(J));
|
||
|
}
|
||
|
|
||
|
/* Narrowing of modulo operator. */
|
||
|
TRef lj_opt_narrow_mod(jit_State *J, TRef rb, TRef rc, TValue *vc)
|
||
|
{
|
||
|
TRef tmp;
|
||
|
if (tvisstr(vc) && !lj_strscan_num(strV(vc), vc))
|
||
|
lj_trace_err(J, LJ_TRERR_BADTYPE);
|
||
|
if ((LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) &&
|
||
|
tref_isinteger(rb) && tref_isinteger(rc) &&
|
||
|
(tvisint(vc) ? intV(vc) != 0 : !tviszero(vc))) {
|
||
|
emitir(IRTGI(IR_NE), rc, lj_ir_kint(J, 0));
|
||
|
return emitir(IRTI(IR_MOD), rb, rc);
|
||
|
}
|
||
|
/* b % c ==> b - floor(b/c)*c */
|
||
|
rb = lj_ir_tonum(J, rb);
|
||
|
rc = lj_ir_tonum(J, rc);
|
||
|
tmp = emitir(IRTN(IR_DIV), rb, rc);
|
||
|
tmp = emitir(IRTN(IR_FPMATH), tmp, IRFPM_FLOOR);
|
||
|
tmp = emitir(IRTN(IR_MUL), tmp, rc);
|
||
|
return emitir(IRTN(IR_SUB), rb, tmp);
|
||
|
}
|
||
|
|
||
|
/* Narrowing of power operator or math.pow. */
|
||
|
TRef lj_opt_narrow_pow(jit_State *J, TRef rb, TRef rc, TValue *vc)
|
||
|
{
|
||
|
if (tvisstr(vc) && !lj_strscan_num(strV(vc), vc))
|
||
|
lj_trace_err(J, LJ_TRERR_BADTYPE);
|
||
|
/* Narrowing must be unconditional to preserve (-x)^i semantics. */
|
||
|
if (tvisint(vc) || numisint(numV(vc))) {
|
||
|
int checkrange = 0;
|
||
|
/* Split pow is faster for bigger exponents. But do this only for (+k)^i. */
|
||
|
if (tref_isk(rb) && (int32_t)ir_knum(IR(tref_ref(rb)))->u32.hi >= 0) {
|
||
|
int32_t k = numberVint(vc);
|
||
|
if (!(k >= -65536 && k <= 65536)) goto split_pow;
|
||
|
checkrange = 1;
|
||
|
}
|
||
|
if (!tref_isinteger(rc)) {
|
||
|
if (tref_isstr(rc))
|
||
|
rc = emitir(IRTG(IR_STRTO, IRT_NUM), rc, 0);
|
||
|
/* Guarded conversion to integer! */
|
||
|
rc = emitir(IRTGI(IR_CONV), rc, IRCONV_INT_NUM|IRCONV_CHECK);
|
||
|
}
|
||
|
if (checkrange && !tref_isk(rc)) { /* Range guard: -65536 <= i <= 65536 */
|
||
|
TRef tmp = emitir(IRTI(IR_ADD), rc, lj_ir_kint(J, 65536));
|
||
|
emitir(IRTGI(IR_ULE), tmp, lj_ir_kint(J, 2*65536));
|
||
|
}
|
||
|
return emitir(IRTN(IR_POW), rb, rc);
|
||
|
}
|
||
|
split_pow:
|
||
|
/* FOLD covers most cases, but some are easier to do here. */
|
||
|
if (tref_isk(rb) && tvispone(ir_knum(IR(tref_ref(rb)))))
|
||
|
return rb; /* 1 ^ x ==> 1 */
|
||
|
rc = lj_ir_tonum(J, rc);
|
||
|
if (tref_isk(rc) && ir_knum(IR(tref_ref(rc)))->n == 0.5)
|
||
|
return emitir(IRTN(IR_FPMATH), rb, IRFPM_SQRT); /* x ^ 0.5 ==> sqrt(x) */
|
||
|
/* Split up b^c into exp2(c*log2(b)). Assembler may rejoin later. */
|
||
|
rb = emitir(IRTN(IR_FPMATH), rb, IRFPM_LOG2);
|
||
|
rc = emitir(IRTN(IR_MUL), rb, rc);
|
||
|
return emitir(IRTN(IR_FPMATH), rc, IRFPM_EXP2);
|
||
|
}
|
||
|
|
||
|
/* -- Predictive narrowing of induction variables ------------------------- */
|
||
|
|
||
|
/* Narrow a single runtime value. */
|
||
|
static int narrow_forl(jit_State *J, cTValue *o)
|
||
|
{
|
||
|
if (tvisint(o)) return 1;
|
||
|
if (LJ_DUALNUM || (J->flags & JIT_F_OPT_NARROW)) return numisint(numV(o));
|
||
|
return 0;
|
||
|
}
|
||
|
|
||
|
/* Narrow the FORL index type by looking at the runtime values. */
|
||
|
IRType lj_opt_narrow_forl(jit_State *J, cTValue *tv)
|
||
|
{
|
||
|
lua_assert(tvisnumber(&tv[FORL_IDX]) &&
|
||
|
tvisnumber(&tv[FORL_STOP]) &&
|
||
|
tvisnumber(&tv[FORL_STEP]));
|
||
|
/* Narrow only if the runtime values of start/stop/step are all integers. */
|
||
|
if (narrow_forl(J, &tv[FORL_IDX]) &&
|
||
|
narrow_forl(J, &tv[FORL_STOP]) &&
|
||
|
narrow_forl(J, &tv[FORL_STEP])) {
|
||
|
/* And if the loop index can't possibly overflow. */
|
||
|
lua_Number step = numberVnum(&tv[FORL_STEP]);
|
||
|
lua_Number sum = numberVnum(&tv[FORL_STOP]) + step;
|
||
|
if (0 <= step ? (sum <= 2147483647.0) : (sum >= -2147483648.0))
|
||
|
return IRT_INT;
|
||
|
}
|
||
|
return IRT_NUM;
|
||
|
}
|
||
|
|
||
|
#undef IR
|
||
|
#undef fins
|
||
|
#undef emitir
|
||
|
#undef emitir_raw
|
||
|
|
||
|
#endif
|