[LLVMdev] Can simplifycfg kill llvm.lifetime intrinsics?
kparzysz at codeaurora.org
Wed Dec 26 14:37:48 PST 2012
On 12/26/2012 3:38 PM, Nick Lewycky wrote:
> Of course you can re-start memory that's been ended... if that isn't
> clear in the langref, please fix.
There are several things that aren't clear (at least when I read it).
%a = phi i32* ..., [ %a.next, %block ]
llvm.lifetime.end(4, %a) <-- (1)
%a.next = getelementptr i32* %a, 1
Does (1) mean the end of lifetime for the 4 bytes that %a happens to be
pointing to in the current iteration? My guess is "yes".
%a = i32* ...
llvm.lifetime.end(4, %a) <-- (2)
%b = load i32 %ptr <-- (3)
Is (2) a guarantee that *%ptr and *%a are not aliased?
If (2) and (3) were in the opposite order, would it be illegal to move
(3) past (2)?
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