Hi,
It looks like, because of the recur, the compiler fails to notice that if
returns a primitive.
As far as I understand in Compiler.java, RecurExpr does not implement
MaybePrimitiveExpr and thus causes on canEmitPrimitive the surrounding
IfExpr to return false.
Someone to confirm this analysis?
On Tue, Nov 20, 2012 at 4:34 PM, Gunnar Völkel <
gunnar.voel...@googlemail.com> wrote:
> I have written a primitive function for exponentiation with integers as
> power using the multiply-and-square algorithm.
> For performance reasons I used primitive type hints for the arguments and
> the return value.
> Profiling the whole application I noticed that there are a lot of
> java.lang.Double/valueOf calls.
> Looking at the bytecode I see that in Clojure 1.3 as well as in Clojure
> 1.4 the result value gets boxed and unboxed like
> Double.valueOf(result).doubleValue().
>
> Am I doing something wrong? Is there a serious bug related to the support
> of primitive functions?
>
> The source code:
>
> (defn first-bit?
> {:inline (fn [n] `(== 1 (clojure.lang.Numbers/and ~n, 1)) )}
> [^long n]
> (== 1 (clojure.lang.Numbers/and n, 1)))
>
> (defn exp-int
> ^double [^double x, ^long c]
> (loop [result 1.0, factor x, c c]
> (if (> c 0)
> (recur
> (if (first-bit? c)
> (* result factor)
> result),
> (* factor factor),
> (bit-shift-right c 1))
> result)))
>
> Last lines of the Java bytecode of `exp-int`:
> 59 dload 5; /* result */
> 61 invokestatic 40; /* java.lang.Double
> java.lang.Double.valueOf(double c) */
> 64 checkcast 85; /* java.lang.Number */
> 67 invokevirtual 89; /* double doubleValue() */
> 70 dreturn;
>
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