Re: [PATCH] Unshare constants in the constant pool (PR target/42894)

[Jeff Law <law at redhat dot com>]

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On 01/26/11 12:37, Jakub Jelinek wrote:
> Hi!
> 
> As discussed in the PR, if a non-shareable constant is force_const_mem
> and the original expression is used elsewhere in the IL (e.g. in REG_EQUAL
> or REG_EQUIV note), unshare_all_rtl doesn't unshare it, but modification of
> the IL might result in changes of the constant in theory and if
> avoid_constant_pool_reference result is then pushed somewhere else into the
> IL, we get RTL sharing errors (as on arm on this testcase).
Well, one could easily argue that using the original expression in the
REG_EQUAL note is incorrect as well.  In fact, looking over all the
calls to set_unique_reg_note shows that most either copy the value or
generate a new one.

I think that means we actually want both the varasm.c and the expr.c
change to avoid incorrect sharing.

jeff

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