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 Post subject: __FP_BASE__的說明
PostPosted: Wed May 16, 2012 11:49 am 
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Joined: Fri Mar 04, 2011 9:36 pm
Posts: 500
主要是由 post-opt 加入的, linker則是負責填上值
__FP_BASE__是用來做 fp-as-gp optimization

例如
lwi.gp $r0, [+0]
lwi.gp $r1, [+4]
lwi.gp $r2, [+8]
lwi.gp $r3, [+12]
這樣需要 4*4 = 16 bytes

但改成
addi.gp $fp, __FP_BASE__ ; la $fp, __FP_BASE__
lwi37.fp $r0, [+0]
lwi37.fp $r1, [+4]
lwi37.fp $r2, [+8]
lwi37.fp $r3, [+12]
則只要 4 + 2*4 = 12 bytes

一般來說, la $fp, __FP_BASE__這道會在要做這個 optimization的function prologue


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