DSE will currently only remove stores in the same block unless they can
be guaranteed to be loop invariant. This expands that to any stores that
are in the same Loop, at the same loop level. This should still account
for where AA/MSSA will not handle aliasing between loops, but allow the
dead stores to be removed where they overlap in the same loop iteration.
It requires adding loop info to DSE, but that looks fairly harmless.
The test case this helps is from code like this, which can come up in
certain matrix operations:
for(i=..)
dst[i] = 0;
for(j=..)
dst[i] += src[i*n+j];
After LICM, this becomes:
for(i=..)
dst[i] = 0;
sum = 0;
for(j=..)
sum += src[i*n+j];
dst[i] = sum;
The first store is dead, and with this patch is now removed.
Differntial Revision: https://reviews.llvm.org/D100464
DSE will currently only remove stores in the same block unless they can
be guaranteed to be loop invariant. This expands that to any stores that
are in the same Loop, at the same loop level. This should still account
for where AA/MSSA will not handle aliasing between loops, but allow the
dead stores to be removed where they overlap in the same loop iteration.
It requires adding loop info to DSE, but that looks fairly harmless.
The test case this helps is from code like this, which can come up in
certain matrix operations:
for(i=..)
dst[i] = 0;
for(j=..)
dst[i] += src[i*n+j];
After LICM, this becomes:
for(i=..)
dst[i] = 0;
sum = 0;
for(j=..)
sum += src[i*n+j];
dst[i] = sum;
The first store is dead, and with this patch is now removed.
Differntial Revision: https://reviews.llvm.org/D100464
This moves the isOverwrite function into the DSEState so that it can
share the analyses and members from the state.
A few extra loop tests were also added to test stores in and around
multi block loops for D100464.
The MemorySSA-based implementation has been enabled without issue
for a while now, so keeping the old implementation around doesn't
seem useful anymore. This drops the MemDep-based implementation.
Differential Revision: https://reviews.llvm.org/D97877
David Green