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This avoids the need for a function call and up to two property lookups for a `Math.pow()` invocation, as well as allowing expressions like `2 ** 16` to be inlined at compile time. Exponentiation uses the same internal handler as `Math.pow()`, per the ES7 specification. Usage: x = base ** exp; x **= 2;pull/987/head
Bruce Pascoe
8 years ago
10 changed files with 180 additions and 115 deletions
@ -0,0 +1,70 @@ |
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/*
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* Shared helpers for arithmetic operations |
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*/ |
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#include "duk_internal.h" |
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/* Shared helper for Math.pow() and exponentiation operator */ |
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DUK_INTERNAL double duk_js_arith_pow(double x, double y) { |
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/* The ANSI C pow() semantics differ from Ecmascript.
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* |
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* E.g. when x==1 and y is +/- infinite, the Ecmascript required |
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* result is NaN, while at least Linux pow() returns 1. |
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*/ |
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duk_small_int_t cx, cy, sx; |
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DUK_UNREF(cx); |
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DUK_UNREF(sx); |
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cy = (duk_small_int_t) DUK_FPCLASSIFY(y); |
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if (cy == DUK_FP_NAN) { |
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goto ret_nan; |
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} |
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if (DUK_FABS(x) == 1.0 && cy == DUK_FP_INFINITE) { |
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goto ret_nan; |
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} |
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#if defined(DUK_USE_POW_NETBSD_WORKAROUND) |
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/* See test-bug-netbsd-math-pow.js: NetBSD 6.0 on x86 (at least) does not
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* correctly handle some cases where x=+/-0. Specific fixes to these |
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* here. |
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*/ |
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cx = (duk_small_int_t) DUK_FPCLASSIFY(x); |
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if (cx == DUK_FP_ZERO && y < 0.0) { |
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sx = (duk_small_int_t) DUK_SIGNBIT(x); |
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if (sx == 0) { |
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/* Math.pow(+0,y) should be Infinity when y<0. NetBSD pow()
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* returns -Infinity instead when y is <0 and finite. The |
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* if-clause also catches y == -Infinity (which works even |
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* without the fix). |
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*/ |
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return DUK_DOUBLE_INFINITY; |
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} else { |
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/* Math.pow(-0,y) where y<0 should be:
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* - -Infinity if y<0 and an odd integer |
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* - Infinity otherwise |
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* NetBSD pow() returns -Infinity for all finite y<0. The |
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* if-clause also catches y == -Infinity (which works even |
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* without the fix). |
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*/ |
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/* fmod() return value has same sign as input (negative) so
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* the result here will be in the range ]-2,0], 1 indicates |
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* odd. If x is -Infinity, NaN is returned and the odd check |
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* always concludes "not odd" which results in desired outcome. |
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*/ |
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double tmp = DUK_FMOD(y, 2); |
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if (tmp == -1.0) { |
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return -DUK_DOUBLE_INFINITY; |
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} else { |
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/* Not odd, or y == -Infinity */ |
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return DUK_DOUBLE_INFINITY; |
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} |
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} |
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} |
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#endif |
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return DUK_POW(x, y); |
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ret_nan: |
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return DUK_DOUBLE_NAN; |
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} |
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