junparser added inline comments.
================
Comment at: clang/lib/CodeGen/CGExprScalar.cpp:2120
+ } else
+ Addr = EmitLValue(E).getAddress(CGF);
Addr = Builder.CreateElementBitCast(Addr, CGF.ConvertTypeForMem(DestTy));
----------------
efriedma wrote:
> junparser wrote:
> > junparser wrote:
> > > efriedma wrote:
> > > > I don't think it's legal to use EmitLValue here at all; the emitted IR
> > > > could have side-effects.
> > > >
> > > > Since we have the vector insert/extract intrinsics now, can we just use
> > > > them here instead of going through the load/store dance?
> > > > I don't think it's legal to use EmitLValue here at all; the emitted IR
> > > > could have side-effects.
> > > >
> > > I agree since we have already visited E.
> > >
> > > > Since we have the vector insert/extract intrinsics now, can we just use
> > > > them here instead of going through the load/store dance?
> > >
> > > we have already use insert/extract intrinsics for same element type, we
> > > can only handle predicate cast through memory.
> > > One of idea here is always use store + load. what do you think?
> > >
> > @efriedma I'm also working on a patch that optimize such store + bitcast +
> > load pattern with constant vector, so maybe it is ok to always use alloca +
> > load
> I'd be happy to accept just unconditionally doing the alloca+store+load thing
> for now.
>
> Not sure I understand why predicates are special here. Even if we can't
> handle predicates directly in insert/extract intrinsics, we can always just
> zero-extend to a bigger integer type, do the cast, then truncate the result.
I'm not sure whether zext+cast+trunc to vxi1 can generate better code. I think
it is better to handle this in llvm ir without extend and truncate, only
bitcast and insert/extract
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D105097/new/
https://reviews.llvm.org/D105097
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