From: Clemens Fruhwirth <clemens@endorphin.org>
Date: Wed, 12 Sep 2007 09:44:30 +0000 (+0000)
Subject: Sign extension hack to work around PC64 relocation limitation for binutils <2.17... 
X-Git-Url: http://git.megacz.com/?a=commitdiff_plain;h=b8a64b8ec9cd3d8f6e3f23e44312c4903eccac45;hp=b8a64b8ec9cd3d8f6e3f23e44312c4903eccac45;p=ghc-hetmet.git

Sign extension hack to work around PC64 relocation limitation for binutils <2.17 for x86_64.

binutils <2.17 can't generate PC64 relocations for x86_64. Hence we
emit only 32 bit PC relative offsets, and artifically stick a zero in
front of them to make them 64 bit (see PprMach.sh ppr_item in
pprDataItem). This works as long as the offset is <32bit AND it's
positive. This is not the case for offsets in jump tables, they are
all negative. This hack sign extends them with a MOVSXL instruction
into the dead index register, then adding the properly sign extended
offset to the jump table base label giving the correct target address
for the following jump.
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