RFR (S): 8161334: C2: Cast nodes hinder memory alias analysis
vladimir.kozlov at oracle.com
Wed Feb 13 17:51:06 UTC 2019
Should you also take into account casts in following Allocation checks
at line #1072?
On 2/12/19 2:32 PM, Vladimir Ivanov wrote:
> The following IR is produced for the slow case reported in the bug:
> B = CastPP (DecodeN ...) // ...$C:NotNull
> S = StoreI M (AddP ( B) #off) V // ...$C:NotNull
> L = LoadI S (AddP (CheckCastPP B) #off) // ...$C:NotNull:exact
> MemNode::can_see_stored_value() can't prove S & L access the same
> location since AddPs are different (since base nodes differ). There's a
> special case there, but only when Allocate is a base.
> Proposed patch generalizes existing Allocate case to the case when both
> base & offset are known to be the same.
> Testing: hs-precheckin-comp, tier1-5
> Best regards,
> Vladimir Ivanov
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