[PATCH] D101245: [GlobalOpt] Disable heap SROA when GEP of the only storer is used

[Fangrui Song via Phabricator via llvm-commits]

MaskRay added inline comments.


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Comment at: llvm/lib/Transforms/IPO/GlobalOpt.cpp:1016
-    // Must index into the array and into the struct.
-    if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
-      if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
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aeubanks wrote:
> seems like this doesn't take into account when the global variable is an array.
> normally, if we just have a normal struct, the GEP's first operand is the GV, second operand is something like 0, and the third operand indexes into the struct itself, which is fine for SROA. having fewer than 3 operands can directly reference the struct
> with an array, we need to account for an extra index to index into the array
> 
Do you have specific suggestion to the diff? :)

I am thinking the value of array heap SROA is low but I don't want to just remove the implementation, so drop GEP - see the tests like heap-sra-phi.ll, heap SROA still works if the function allocates and forgets the array.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D101245/new/

https://reviews.llvm.org/D101245