[MachineCopyPropagation] Extend pass to do COPY source forwarding

This change extends MachineCopyPropagation to do COPY source forwarding.

This change also extends the MachineCopyPropagation pass to be able to
be run during register allocation, after physical registers have been
assigned, but before the virtual registers have been re-written, which
allows it to remove virtual register COPY LiveIntervals that become dead
through the forwarding of all of their uses.

Reviewers: qcolombet, javed.absar, MatzeB, jonpa

Subscribers: jyknight, nemanjai, llvm-commits, nhaehnle, mcrosier, mgorny

Differential Revision: https://reviews.llvm.org/D30751

llvm-svn: 311038

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/CodeGen.cpp b/llvm/lib/CodeGen/CodeGen.cpp
index b7fd45a3f6a..c92b45a752e 100644
--- a/llvm/lib/CodeGen/CodeGen.cpp
+++ b/llvm/lib/CodeGen/CodeGen.cpp
@@ -54,6 +54,7 @@ void llvm::initializeCodeGen(PassRegistry &Registry) {
   initializeMachineCSEPass(Registry);
   initializeMachineCombinerPass(Registry);
   initializeMachineCopyPropagationPass(Registry);
+  initializeMachineCopyPropagationPreRegRewritePass(Registry);
   initializeMachineDominatorTreePass(Registry);
   initializeMachineFunctionPrinterPassPass(Registry);
   initializeMachineLICMPass(Registry);