fhahn added inline comments.
================
Comment at: llvm/lib/Transforms/Scalar/DeadStoreElimination.cpp:312
switch (II->getIntrinsicID()) {
default: llvm_unreachable("doesn't pass 'hasAnalyzableMemoryWrite'
predicate");
case Intrinsic::lifetime_end:
----------------
asbirlea wrote:
> The crash is hitting this unreachable for the intrinsic "llvm.memcpy.inline".
> Simple repro: opt -dse test1.ll
> ```
> define void @test(i8* noalias nocapture %0, i8* noalias nocapture readonly
> %1) {
> tail call void @llvm.memcpy.inline(i8* align 1 %0, i8* align 1 %1, i64 3,
> i1 false)
> ret void
> }
>
> declare void @llvm.memcpy.inline(i8* noalias nocapture writeonly, i8* noalias
> nocapture readonly, i64 immarg, i1 immarg)
> ```
Thanks! The problem was that MemorySSA-based DSE only relies on whether we can
find read/write memory locations. For `memcpy.inline`, MemoryLocation knows how
to extract the arguments, but the DSE functions where not updated to account
for that.
In the legacy DSE, we silently failed to optimized/eliminate `memcpy.inline`
calls, but with the MemorySSA version we got a crash highlighting that the code
needs updating.
That should be fixed by a5ec99da6ea7
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D87163/new/
https://reviews.llvm.org/D87163
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