+
+ // Verify that the copied-from memory doesn't change in between the two
+ // transfers. For example, in:
+ // memcpy(a <- b)
+ // *b = 42;
+ // memcpy(c <- a)
+ // It would be invalid to transform the second memcpy into memcpy(c <- b).
+ //
+ // TODO: If the code between M and MDep is transparent to the destination "c",
+ // then we could still perform the xform by moving M up to the first memcpy.
+ //
+ // NOTE: This is conservative, it will stop on any read from the source loc,
+ // not just the defining memcpy.
+ MemDepResult SourceDep =
+ MD->getPointerDependencyFrom(AA.getLocationForSource(MDep),
+ false, M, M->getParent());
+ if (!SourceDep.isClobber() || SourceDep.getInst() != MDep)
+ return false;