[PATCH] D31924: SROA: Allow eliminating addrspacecasted allocas

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy added inline comments.


================
Comment at: lib/Transforms/Scalar/SROA.cpp:1557
+    unsigned Opc = Operator::getOpcode(Ptr);
+    if (Opc == Instruction::BitCast || Opc == Instruction::AddrSpaceCast) {
       Ptr = cast<Operator>(Ptr)->getOperand(0);
----------------
arsenm wrote:
> sanjoy wrote:
> > Are you ruling that `GEP(CAST(X), 1)` is the same as `CAST(GEP X, 1)`?  If so, I'm not sure this is correct given your constraint on address space casts.
> > 
> > For instance, if casting from address space N to M, with both spaces having the same pointer width, involves flipping the high and low halves of the pointer then `GEP(CAST(X), 1)` is not the same as `(CAST(GEP X, 1))`.
> > 
> > Of course, this means that GEPs over pointers of address space M are different operations from GEPs over pointers of address space N, but that's allowed, AFAIK.
> > 
> Yes, those should be the same
Then you need to change the langref to disallow address space casts as the above (flipping the high and low halfs of the pointer).


https://reviews.llvm.org/D31924