[LLVMdev] [PATCH / PROPOSAL] bitcode encoding that is ~15% smaller for large bitcode files...
jvoung at chromium.org
Wed Sep 26 14:08:34 PDT 2012
On Wed, Sep 26, 2012 at 2:07 AM, Renato Golin <rengolin at systemcall.org>wrote:
> On 26 September 2012 01:08, Jan Voung <jvoung at chromium.org> wrote:
> > - Forward references will create negative-valued ids (which end up being
> > written out as large 32-bit integers, as far as I could tell).
> Can you use an SLEB-like representation?
> It's probably not going to be backwards compatible, but if there isn't
> an SLEB/ULEB representation in bitcode, I'd say it's a good
> improvement. ;)
I think most of the instructions operands are encoded as VBR(N)
for some N number of bits, and it seems to me that VBR(8) is like ULEB?
I think that the default N is 6 bits, but I haven't tried tweaking these
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