questions about memory dependence analysis

Hi,

    I have tried memory dependence analysis. I found that load could have def dependence on another load. How could this happen? And what does clobber dependence mean?

    Thanks a lot!

    Best,

                                                                        Linhai

    I have tried memory dependence analysis. I found that load could have
def dependence on another load. How could this happen? And what does
clobber dependence mean?

  For example, we may have two 32-bit register R0 and R1, and [R0,R1] can
be considered as one 64-bit register X1. When you load X1, this
operation actually affect R0 and R1. If you have another load R0, we can
say those load instructions have dependence.

  From the comment of the source code [1], clobber dependence means the
content of some memory locations (X) that we cares is modified by a store
instruction, thus "load X" might have clobber dependence with the store
instruction.

HTH,
chenwj

[1]
http://llvm.org/docs/doxygen/html/MemoryDependenceAnalysis_8h_source.html

Thanks a lot!

Best,

Linhai