https://bugs.webkit.org/show_bug.cgi?id=99706
--- Comment #18 from Balazs Kilvady <kilvadyb at homejinni.com> 2012-10-24 11:31:31 PST ---
(In reply to comment #14)
> (From update of attachment 169392 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=169392&action=review
>
> > Source/JavaScriptCore/offlineasm/mips.rb:398
> > + if scaleShift == 0
> > + tmp0 = Tmp.new(codeOrigin, :gpr)
> > + list << Instruction.new(codeOrigin, "addp", [base, index, tmp0])
> > + Address.new(codeOrigin, tmp0, Immediate.new(codeOrigin, offset.value));
>
> scaleShift will never be 0.
There is 0 scaleShift so I would like to keep that checking. For example at LowLevelInterpreter.asm:602:
loadp VectorBufferOffset[scratch, dest, 1], dest
The generated armv7 code:
"\tmovw r9, #4\n"
"\tadd r9, r1\n"
"\tldr r0, [r9, r0, lsl #0]\n"
The mips equivalent is (without scaleShift == 0 check):
"\tsll $t7, $v0, 0\n"
"\taddu $t7, $t7, $v1\n"
"\tlw $v0, 4($t7)\n"
And on mips with scaleShift checking:
"\taddu $t7, $v1, $v0\n"
"\tlw $v0, 4($t7)\n"
Both (with or without scaleShift checking) passes Tools/Scripts/run-javascriptcore-tests. I guess 2^0 == 1 so scale == 1; scaleShift == 0;
As ast.rb has:
def scaleShift
case scale
when 1
0
when 2
1
when 4
2
when 8
3
else
raise "Bad scale at #{codeOriginString}"
end
end
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