Splitting basic blocks into multiple statements if there are now
additional scalar dependencies gives more freedom to the scheduler, but
more statements also means higher compile-time complexity. Switch to
finer statement granularity, the additional compile time should be
limited by the number of operations quota.
The regression tests are written for the -polly-stmt-granularity=bb
setting, therefore we add that flag to those tests that break with the
new default. Some of the tests only fail because the statements are
named differently due to a basic block resulting in multiple statements,
but which are removed during simplification of statements without
side-effects. Previous commits tried to reduce this effect, but it is
not completely avoidable.
Differential Revision: https://reviews.llvm.org/D42151
llvm-svn: 324169
Use a mark-and-sweep algorithm to find and remove unused instructions
and MemoryAccesses. This is useful in particular to remove scalar
writes that are never used anywhere. A scalar write in a loop induces
a write-after-write dependency that stops the loop iterations to be
rescheduled. Such writes can be a result of previous transformations
such as DeLICM and operand tree forwarding.
It adds a new class VirtualInstruction that represents an instruction in
a particular statement. At the moment an instruction can only belong to
the statement that represents a BasicBlock. In the future, instructions
can be in one of multiple statements representing a BasicBlock
(Nandini's work), in different statements than its BasicBlock would
indicate, and even multiple statements at once (by forwarding operand
trees). It also integrates nicely with the VirtualUse class.
ScopStmt::contains(Instruction*) currently uses the instruction's parent
BasicBlock to check whether it contains the instruction. It will need to
check the actual statement list when one of the aforementioned features
become possible.
Differential Revision: https://reviews.llvm.org/D35656
llvm-svn: 308626
Pengxuan Zheng