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<h1>The GHC Commentary - The Native Code Generator</h1>
<p>
- On x86 and sparc platforms, GHC can generate assembly code
+ On some platforms (currently x86 and PowerPC, with bitrotted
+ support for Sparc and Alpha), GHC can generate assembly code
directly, without having to go via C. This can sometimes almost
halve compilation time, and avoids the fragility and
- horribleness of the mangler. The NCG is enabled by default for
- non-optimising compilation on x86 and sparc. For most programs
- it generates code which runs only about 1% slower than that
+ horribleness of the <a href="mangler.html">mangler</a>. The NCG
+ is enabled by default for
+ non-optimising compilation on supported platforms. For most programs
+ it generates code which runs only 1-3% slower
+ (depending on platform and type of code) than that
created by gcc on x86s, so it is well worth using even with
optimised compilation. FP-intensive x86 programs see a bigger
- slowdown, and all sparc code runs about 5% slower due to
+ slowdown, and all Sparc code runs about 5% slower due to
us not filling branch delay slots.
<p>
- In the distant past
- the NCG could also generate Alpha code, and that machinery
- is still there, but will need extensive refurbishment to
- get it going again, due to underlying infrastructural changes.
- Budding hackers thinking of doing a PowerPC port would do well
- to use the sparc bits as a starting point.
- <p>
The NCG has always been something of a second-class citizen
inside GHC, an unloved child, rather. This means that its
integration into the compiler as a whole is rather clumsy, which
proper is fairly cleanly designed, as target-independent as it
reasonably can be, and so should not be difficult to retarget.
<p>
- The following details are correct as per the CVS head of end-Jan
- 2002.
+ <b>NOTE!</b> The native code generator was largely rewritten as part
+ of the C-- backend changes, around May 2004. Unfortunately the
+ rest of this document still refers to the old version, and was written
+ with relation to the CVS head as of end-Jan 2002. Some of it is relevant,
+ some of it isn't.
<h2>Overview</h2>
The top-level code generator fn is
projects / ghc-hetmet.git / commitdiff