search for: globalsaa

Hi James, Thanks for the help. From the log, I could infer that SLP vectorizer is not preserving alias analysis, preventing GVN from getting the info. Although the first function to get compiled has GlobalsAA available during GVN, rest of them do not as SLP vectorizer run on that function invalidates GlobalsAA which is a module pass. Is there a way to force re-computation of a particular analysis? As a side note, I didn't have this problem on release_37. Thanks a lot. Regards, - Vaivaswatha O...

>You could, in the LTO pipeline, reinsert GlobalsAA after the SLPVectorizer (not saying you should). I didn't realise that adding GlobalsAA* after* SLPVectorizer could help. Thanks for this tip. >There is something fishy. Do you have a test case that reproduce with llvm-lto? I'm currently looking at a proprietary benchmark. I'll try...

Hi Mehdi, Thank you for the response. I'm actually on an LTO setup and was referring to PassManagerBuilder::addLTOOptimizationPasses. Here, GlobalsAA is scheduled to run well ahead of SLPVectorizer. However since GlobalsAA is a module pass, it runs once and a bunch of passes, including SLPVectorizer is run for each function. When one of them invalidates the analysis, rest of the functions do not have it available. Both LICM and GVN face the same...

...th for the inputs. I've created a patch for the same, please review: http://reviews.llvm.org/D15185 >You can specifically insert it into the pass pipeline, but in this case, we should just fix SLP to preserve the analysis. @Hal, I tried doing this but it didn't seem to work. I added the GlobalsAA pass right before GVN but it didn't seem to help. In retrospect, looking at the way pass manager works, it looks like it wasn't of much use. Since GlobalsAA is a ModulePass, and FunctionPasses that are scheduled even later are run first, those FunctionPasses that invalidate it do so for goo...

Hi, I've noticed that alias analysis queries arising from GVN do not use the results from GlobalsAA. The last call to AAResultsWrapperPass::runOnFunction() before GVN does not add GlobalsAAWrapperPass due to unavailability. This leads to the alias queries from GVN not having any globals mod-ref info. Is this a known issue? and is there any way to have globals mod-ref info available for GVN? Tha...

Hi, GlobalsAA, during propagation of mod-ref behavior in the call graph, looks at library functions (in GlobalsAAResult::AnalyzeCallGraph: F->isDeclaration() check), for attributes, and if the function does not have the onlyReadsMemory attribute set, forgets it. I noticed that library functions such as mallo...

...up malloc hooks (assuming we're in a whole program compilation) and make assumptions (such as onlyAccessesArgMem()) when the program hasn't setup malloc hooks? Using a command line flag could be one option too. I'm currently working on a program where having these attributes could help GlobalsAA give significantly more precise results. Considering that this info is propagated to the caller, its caller and so on, this may have a wider impact than the program I'm currently looking at. Thanks, - Vaivaswatha On Thu, Dec 3, 2015 at 2:57 PM, James Molloy <james at jamesmolloy.co.uk&g...

...act outside of LTO anyway. >>> I think you're understanding correctly, but I don't understand what you're saying will go badly with the malloc example. Quoting the start of the thread: <<< The intention behind introducing this attribute is to relax the conditions in GlobalsAA as below: (this code is in GlobalsAAResult::AnalyzeCallGraph) if (F->isDeclaration()) { // Try to get mod/ref behaviour from function attributes. - if (F->doesNotAccessMemory()) { + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { //...

...understanding correctly, but I don't understand what > > you're saying will go badly with the malloc example. Quoting the > > start of the thread: > > > > <<< > > The intention behind introducing this attribute is to relax the > > conditions in GlobalsAA as below: > > (this code is in GlobalsAAResult::AnalyzeCallGraph) > > if (F->isDeclaration()) { > > // Try to get mod/ref behaviour from function attributes. > > - if (F->doesNotAccessMemory()) { > > + if (F->doesNotAccessMemory() |...

...rstand > > > what > > > you're saying will go badly with the malloc example. Quoting the > > > start of the thread: > > > > > > <<< > > > The intention behind introducing this attribute is to relax the > > > conditions in GlobalsAA as below: > > > (this code is in GlobalsAAResult::AnalyzeCallGraph) > > > if (F->isDeclaration()) { > > > // Try to get mod/ref behaviour from function attributes. > > > - if (F->doesNotAccessMemory()) { > > > + if (F-&g...

...in the call > graph. (Do this in FunctionAttrs.cpp?). > 5. Since ReadNone and ArgMemOnly has now been redfined, all > optimizations that rely on these flags for safety now also need to > check the new "HasInaccessibleState" flag and make sure it isn't > present. > 6. GlobalsAA will be modified according to the diff in the first mail > in this email thread. > The alternative approach that was discussed would involve the > following changes: > (Approach B) > 1. Define new attributes AlmostReadNone and AlmostArgMemOnly, (with > the "Almost" par...

...or sub, mul and shl. +2% 4. r246694: [RemoveDuplicatePHINodes] Start over after removing a PHI. -1% 5. r247269: [ADT] Rewrite the StringRef::find implementation to be simpler... +1% r247240: [LPM] Use a map from analysis ID to immutable passes in the legacy pass manager... +3% r247264: Enable GlobalsAA by default. +1% 6. r247674: [GlobalsAA] Disable globals-aa by default. -1% 7. r248638: [SCEV] Reapply 'Teach isLoopBackedgeGuardedByCond to exploit trip counts'. +2% 8. r249802: [SCEV] Call `StrengthenNoWrapFlags` after `GroupByComplexity`; NFCI. +4% 9. r250157: [GlobalsAA] Turn GlobalsAA o...

...ttrs.cpp?). >> > 5. Since ReadNone and ArgMemOnly has now been redfined, all >> > optimizations that rely on these flags for safety now also need to >> > check the new "HasInaccessibleState" flag and make sure it isn't >> > present. >> > 6. GlobalsAA will be modified according to the diff in the first mail >> > in this email thread. >> >> > The alternative approach that was discussed would involve the >> > following changes: >> >> > (Approach B) >> > 1. Define new attributes AlmostReadNon...

...ot; upwards in the call graph. (Do this in FunctionAttrs.cpp?). > 5. Since ReadNone and ArgMemOnly has now been redfined, all optimizations that rely on these flags for safety now also > need to check the new "HasInaccessibleState" flag and make sure it isn't present. > 6. GlobalsAA will be modified according to the diff in the first mail in this email thread. > > The alternative approach that was discussed would involve the following changes: > (Approach B) > 1. Define new attributes AlmostReadNone and AlmostArgMemOnly, (with the "Almost" part denoti...

...r246694: [RemoveDuplicatePHINodes] Start over after removing a PHI. -1% >> 5. r247269: [ADT] Rewrite the StringRef::find implementation to be simpler... +1% >> r247240: [LPM] Use a map from analysis ID to immutable passes in the legacy pass manager... +3% >> r247264: Enable GlobalsAA by default. +1% >> 6. r247674: [GlobalsAA] Disable globals-aa by default. -1% >> 7. r248638: [SCEV] Reapply 'Teach isLoopBackedgeGuardedByCond to exploit trip counts'. +2% >> 8. r249802: [SCEV] Call `StrengthenNoWrapFlags` after `GroupByComplexity`; NFCI. +4% >> 9. r...

Sigh... let me try that last part again: Maybe GlobalsAA and/or a GlobalsAA-centric attribution pass could partition writes as: 1. Stores to local allocas 2. Stores through pointer parameters 3. Stores to globals defined in this compilation unit 4. Other Attributing functions with attributes: readonly: only writes of type 1 argmemonly: only...

...eDuplicatePHINodes] Start over after removing a PHI. > -1% > > 5. r247269: [ADT] Rewrite the StringRef::find implementation to be > simpler... +1% > > r247240: [LPM] Use a map from analysis ID to immutable passes in the > legacy pass manager... +3% > > r247264: Enable GlobalsAA by default. +1% > > 6. r247674: [GlobalsAA] Disable globals-aa by default. -1% > > 7. r248638: [SCEV] Reapply 'Teach isLoopBackedgeGuardedByCond to exploit > trip counts'. +2% > > 8. r249802: [SCEV] Call `StrengthenNoWrapFlags` after > `GroupByComplexity`; NFCI. +4%...

...e don't have a specific name for" and all the analyses report "may alias because neither touches anything I have a specific name for". The other way would of course be to make one analysis powerful enough to catch the cases we're concerned with. Would it be workable to have GlobalsAA look through the stores (and other mutating operations) in a function to see if they're: 1. a store to a local alloca 2. a store to a global defined in this compilation unit 3. a store through a pointer parameter 4. a call to a function that it has inferred is "ReadOnly-like" (or...

...ariables such as errno). Example attributes (in addition to what are already set): malloc/free: HasInaccessibleState, ReadNone printf: HasInaccessibleState, ArgMemOnly realloc: HasInaccessibleState, ReadOnly (not sure). The intention behind introducing this attribute is to relax the conditions in GlobalsAA as below: (this code is in GlobalsAAResult::AnalyzeCallGraph) if (F->isDeclaration()) { // Try to get mod/ref behaviour from function attributes. - if (F->doesNotAccessMemory()) { + if (F->doesNotAccessMemory() || F->onlyAccessesArgMemory()) { /...

...mple attributes (in addition to what are already set): > malloc/free: HasInaccessibleState, ReadNone > printf: HasInaccessibleState, ArgMemOnly > realloc: HasInaccessibleState, ReadOnly (not sure). > > The intention behind introducing this attribute is to relax the conditions > in GlobalsAA as below: > (this code is in GlobalsAAResult::AnalyzeCallGraph) > > if (F->isDeclaration()) { > // Try to get mod/ref behaviour from function attributes. > - if (F->doesNotAccessMemory()) { > + if (F->doesNotAccessMemory() || F->onlyAccess...