Reapply CycleInfo: Introduce cycles as a generalization of loops

Reverts 02940d6d2202. Fixes breakage in the modules build.

LLVM loops cannot represent irreducible structures in the CFG. This
change introduce the concept of cycles as a generalization of loops,
along with a CycleInfo analysis that discovers a nested
hierarchy of such cycles. This is based on Havlak (1997), Nesting of
Reducible and Irreducible Loops.

The cycle analysis is implemented as a generic template and then
instatiated for LLVM IR and Machine IR. The template relies on a new
GenericSSAContext template which must be specialized when used for
each IR.

This review is a restart of an older review request:
https://reviews.llvm.org/D83094

Original implementation by Nicolai Hähnle <nicolai.haehnle@amd.com>,
with recent refactoring by Sameer Sahasrabuddhe <sameer.sahasrabuddhe@amd.com>

Differential Revision: https://reviews.llvm.org/D112696

1 files changed, 2 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index bbdd8aa..7c236a9 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -68,6 +68,8 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeMachineCSEPass(Registry);
   initializeMachineCombinerPass(Registry);
   initializeMachineCopyPropagationPass(Registry);
+  initializeMachineCycleInfoPrinterPassPass(Registry);
+  initializeMachineCycleInfoWrapperPassPass(Registry);
   initializeMachineDominatorTreePass(Registry);
   initializeMachineFunctionPrinterPassPass(Registry);
   initializeMachineLICMPass(Registry);