search for: getmodref

...his is odd. On my clang.bc Without: 2.2967 ( 53.8%) 0.0242 ( 26.4%) 2.3210 ( 53.2%) 2.3227 ( 53.2%) Memory SSA 2.3364 ( 53.7%) 0.0246 ( 25.7%) 2.3610 ( 53.1%) 2.3636 ( 53.1%) Memory SSA 2.3353 ( 54.0%) 0.0258 ( 27.0%) 2.3611 ( 53.4%) 2.3632 ( 53.3%) Memory SSA With two getModRefInfo calls: 3.0302 ( 58.8%) 0.0328 ( 29.9%) 3.0630 ( 58.2%) 3.0858 ( 58.2%) Memory SSA 3.0097 ( 58.9%) 0.0325 ( 30.0%) 3.0422 ( 58.3%) 3.0590 ( 58.3%) Memory SSA 3.0486 ( 58.8%) 0.0317 ( 29.4%) 3.0804 ( 58.2%) 3.1331 ( 58.3%) Memory SSA with alias followed by getModRefInf...

...om> > wrote: > >> Hi, >> >> This came up in https://reviews.llvm.org/D38569, and I'd like some input >> on what's the best way to get alias and mod-ref info without having two >> alias calls. >> >> A couple of ideas: >> (a) Extend the getModRefInfo interface (+getModRefBehavior, >> +gerArgModRefInfo) to return a pair {ModRefInfo, AliasResult}. >> >> The AliasResult can be optional based on an argument >> e.g.: >> struct MRI_AR { ModRefInfo MRI, AliasResult AR }; >> MRI_AR getModRefInfoAlias...

...we could do the same. If we determine it's a must-alias of a set of things, we could do the same If we determine it's a must-alias of the live on entry def, etc If I understand correctly, the necessary info for fp in this example is: isMustAlias (CallSite argument a, Value a) && getModRefBehavior(CallSite)== onlyReadsMemory. So adding a MRI_MustMod is insufficient? Are we instead looking to set a MRI_Must bit, disjunct of MRI_Mod, and test for MRI_Ref&MRI_Must or MRI_Mod&MRI_Must? In getModRefInfo(CS, Loc), the MRI_Must bit would then be set if doesAccessArgPointees and Arg...

> In your new proposal, doing & on the result of getModRef() may yield unexpected results. Agreed. I made the change I proposed locally, and, while it simplifies some cases, it makes other bit-wise operations look unintuitive. > Maybe we should just hide all that in inline functions or something and make it an enum class Noted, and looking into this op...

...as a major problem. Please feel free to fix these places > by replacing the equality checks with mask checks. > Ok, thank you! > > > -Hal > > So I guess my question is, what's the right approach here? I feel like I'm > not on the right path. > > >> In getModRefInfo(CS, Loc), the MRI_Must bit would then be set if >>> doesAccessArgPointees and ArgAlias == MustAlias for all Args, which seems >>> correct. >>> >> >> >> alias == MustAlias for Loc, not for all args. >> (IE It it returns a singular result about L...