Re: Compiling to C (where C is used as misspelled assembly)

conway@mundook.cs.mu.OZ.AU (Thomas Charles CONWAY) writes:


>he [Fergus] wrote an equivalent piece
>of C code (all in one module) which passed and returned structures,
>just as the Mercury code did. He tried several C compilers - even
>with `const' in all the right places (etc), the compiler didn't do any
>inlining, and created the intermediate structures even though it
>should have been painfully obvious to do so.


Minor correction: the C compilers did do the inlining.
The problem was that they only optimized away the "call" and "return"
instructions. They didn't optimize away the parameter passing/returning.
They generated code that spent a lot of time unnecessarily
storing data on the stack, copying data from one location on the stack
to another, and then loading it from the stack into registers again.


--
Fergus Henderson <fjh@cs.mu.oz.au>
WWW: <http://www.cs.mu.oz.au/~fjh>
PGP: finger fjh@128.250.37.3
--

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